Tailoring Schottky Barriers and Active Sites in Bi-metallic Cluster Mesoporous Carbon Nitride Heterostructures nanocomposite for Hydrogen Evolution with In-situ insights

Tailoring Schottky Barriers and Active Sites in Bi-metallic Cluster Mesoporous Carbon Nitride Heterostructures nanocomposite for Hydrogen Evolution with In-situ insights | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Tailoring Schottky Barriers and Active Sites in Bi-metallic Cluster Mesoporous Carbon Nitride Heterostructures nanocomposite for Hydrogen Evolution with In-situ insights V Navakoteswara Rao, Kwon hukwon, M Nagaveni, P Ravi, Yonghee Lee, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3971500/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The advancement of photocatalysis relies on the development of novel hetero-structured materials with unique architectures. In this study, we successfully synthesized a hetero-structured g-C 3 N 4 (GCN) material with a distinctive surface modification. To further enhance its photocatalytic performance, we optimized the Ag-Ni concentration to maximize the active sites for hydrogen evolution reactions. By using systematic physicochemical characterizations and density functional theory (DFT) calculations, we elucidated the pivotal role of graphitic carbon nitride (g-C 3 N 4 ) in facilitating the formation of an efficient charge transfer channel and promoting the effective generation and separation of photo-generated carriers. From the DFT calculations, we also demonstrated that the Ag-Ni nanoparticles provide more efficient active sites than Ni nanoparticles for water splitting and hydrogen evolution and In-situ TEM exploration. Furthermore, the hetero microstructure consisting of thin g-C 3 N 4 nano scrolls has a crucial role in shortening the migration distance of the carriers, effectively suppressing carrier recombination. Consequently, these extraordinary characteristics resulted in a superior solar light-driven photocatalytic H 2 evolution rate of 2507 µmol h − 1 g − 1 , surpassing the rate achieved by bulk g-C 3 N 4 by a remarkable 18.6-folds. Moreover, the apparent quantum efficiency of this hetero-structured material reached an exceptional value of 1.6% under a 1.5 G air mass filter. Hetero-structured Surface-active site Solar Photocatalyst and quantum efficiency Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction In recent decades, the world has been confronted with an unparalleled challenge in the form of an energy crisis brought by the surging global population and rapid industrialization. Our growing energy demands have predominantly relied on non-renewable resources like coal, fossil fuels, petrol, and oil, leading to their alarming depletion[ 1 ]. Disturbingly, projections indicate that by 2050, the world's energy requirements will surpass twice the capacity of existing energy supplies[ 2 ]. Beyond depletion, the utilization of these non-renewable sources has inflicted grave damage upon the environment with greenhouse gas emissions being a major concern. It is evident that we need a transformative solution, and renewable energy sources have emerged as the most promising alternative to address these pressing issues. For example, there are many eco-friendly options, including hydroelectricity, biomass, wind, geothermal energy, and solar light that include applications like solar drying and solar cooking[ 3 , 4 ]. One particularly ingenious approach to alleviating the impending energy crisis and environmental degradation lies in harnessing the power of solar energy through photosynthesis[ 5 , 6 ]. By converting solar energy into chemical energy, we can produce environmentally friendly hydrogen gas, which upon consumption, only yields water or water vapours, leaving no harmful traces behind[ 7 ]. Embracing this innovative method not only enables us to meet the future energy demand sustainably but also has a crucial role in safeguarding our planet's fragile ecosystem[ 8 ]. The potential of solar energy harvesting to produce clean hydrogen gas offers a beacon of hope for a greener and more sustainable future[ 9 , 10 ]. As we strive toward a world driven by renewable resources, we pave the path to tackle the energy crisis while upholding our responsibility to protect the environment for evolution[ 11 , 12 ]. Hydrogen, with its impressive heat value of 120–142 MJ kg − 1 , is widely recognized as a clean and efficient source of solar energy. Recently, the global production of hydrogen has exceeded 44.5 million tons, and its prominence as a primary energy source is projected to endure until 2080[ 13 , 14 ]. Amidst the various methods of hydrogen production, photocatalytic water splitting shines as a promising approach, captivating considerable attention for its diverse potential in both environmental and energy applications[ 15 , 16 ]. Artificial photosynthesis, a revolutionary concept, has emerged as one of the most environmentally friendly solutions to tackle the impending crises in energy and the environment[ 6 , 17 , 18 ]. By emulating the natural process of photosynthesis, this innovative technique harnesses the power of sunlight to facilitate the conversion of water into hydrogen gas[ 19 ]. Not only does this method hold tremendous promise in addressing the world's energy needs, but it also offers an elegant and sustainable means to mitigate environmental challenges[ 20 ]. The journey towards a greener and more sustainable future heavily relies on pioneering approaches like photocatalytic water splitting and artificial photosynthesis. By tapping into these cutting-edge technologies, we pave the way for a harmonious coexistence with our planet, ensuring a brighter and cleaner tomorrow for future generations[ 17 , 21 ]. Graphitic carbon nitride (g-C 3 N 4 ) has gained prominence as an efficient photocatalyst due to its remarkable properties[ 22 , 23 ]. First, it exhibits visible light absorption with a bandgap ranging from 2.6 to 2.7 eV, enabling it to harness a substantial portion of the solar spectrum for photocatalytic reactions. Moreover, g-C 3 N 4 demonstrates excellent stability under photocatalytic conditions, ensuring long-term use without significant degradation. Its large specific surface area offers abundant active sites, enhancing its catalytic efficiency[ 24 , 25 ]. These tuneable properties make it versatile, enabling customized materials for specific applications. Furthermore, g-C 3 N 4 is environmentally friendly, composed of earth-abundant elements like carbon and nitrogen unlike catalysts based on rare or toxic elements[ 26 ]. Photocatalytic activity is a benchmark of g-C 3 N 4 , participating in reactions like water splitting, pollutant degradation, CO 2 reduction, and organic synthesis, making it valuable for sustainable energy conversion and environmental remediation[ 27 – 29 ]. Lastly, it boasts cost-effectiveness, as the raw materials for its synthesis are readily available and inexpensive. Due to these attributes, g-C 3 N 4 is widely studied for its potential in various applications[ 30 , 31 ]. The addition of a bimetallic catalyst, typically composed of a photosensitizer (e.g., Ag, Au, and Ni) and a co-catalyst, further enhances its photocatalytic efficiency[ 32 ]. The photosensitizer broadens the light absorption range, including visible light, improving electron-hole pair generation[ 33 , 34 ]. Effective charge carrier separation is crucial because recombination diminishes photocatalytic activity[ 35 ]. The co-catalyst acts as an electron trap, capturing electrons and preventing their recombination with holes. It also boosts catalytic activity by facilitating reduction reactions, such as hydrogen evolution during photocatalytic water splitting. This dual catalyst system enhances hydrogen generation rates and efficiency while improving stability and addresses potential degradation issues during prolonged exposure to light and reaction conditions[ 25 , 36 , 37 ]. Harnessing solar energy for hydrogen generation reduces reliance on fossil fuels and mitigates climate change. The dual (Ag-Ni) catalyst enhances photocatalytic efficiency, significantly reducing the energy consumption required for hydrogen production and thereby promoting a sustainable and eco-friendly approach[ 38 ]. To the best of our knowledge, there is no existing literature on the fabrication of holey grain nanotubes with dual-catalyst deposition for photocatalytic hydrogen generation. Exploring holey grain nanotubes combined with dual co-catalysts has the potential to significantly enhance photocatalytic surface medication properties and active sites[ 39 – 41 ]. In this study, we developed a straightforward and efficient synthesis process to create holey grain g-C 3 N 4 nanotubes/nanosheets heterostructure and successfully incorporated them into a dual catalyst (Ni-Ag) for enhanced hydrogen production. Our optimized photocatalyst demonstrated a remarkable hydrogen generation rate when exposed to simulated solar light irradiation shown by in situ TEM analysis. Notably, the apparent quantum yield and overall UTH (UV-visible-to-hydrogen) conversion efficiency show exceptional performance. To support our findings, we performed density functional theory (DFT) calculations, and the results obtained from our experiments align closely with the theoretical predictions. This synergy between experimental results and theoretical modelling underscores the robustness of our approach and the potential for significant advancements in photocatalytic hydrogen production efficiency. 2. Materials and Methods 2.1 Reagents and Solvents All chemicals were of analytical grade and used without further purification or distillation steps unless otherwise noted: hydroxylamine sulphate (NH 4 OH.H 2 SO 4, Sigma Aldrich, 99%), melamine (C 3 N 4 (NH 2 ) 3 , Sigma Aldrich, 99%), Nickel (II) nitrate (Ni(NO 3 ) 2 , Sigma Aldrich, 99%), NaBH 4 (Fisher Scientific, 99%), Poly Vinyl pyrrolidine (PVP, Merck, 99%), Na 2 So 4 (Sigma Aldrich, 99%), HCl (Sigma Aldrich, 99%), NaOH (Sigma Aldrich, 99%), Nafion solution (Fisher Scientific, 99%), and ethanol (C 2 H 5 OH, Merck, 99.9%). Both ultra-pure water (H 2 O) was utilized for the photocatalytic hydrogen (H 2 ) evolution experiments. 2.2 Experiments (i) The complex Intermediate preparation : In this experimental procedure, we utilized typical hydrothermal processes to synthesize an intermediate compound[ 42 , 43 ]. The process began with the dispersion of 2 g of hydroxylamine sulphate (NH 4 OH.H 2 SO 4 ) and 1 g of melamine (C 3 N 4 (NH 2 ) 3 ) into 35 mL of deionized water. Both precursors were mixed using magnetic stirring for a duration of 30 min. Subsequently, the mixture was carefully transferred into a 50 mL Teflon-lined autoclave and heated to 120°C for a period of 12 h. After the hydrothermal reaction was completed, the resulting product was collected in 50 mL beakers and underwent a series of washing steps. The washing was performed alternately with deionized water and absolute ethanol, repeating the process five times to ensure purity. Finally, the synthesized intermediate compound was dried at 80°C for 12 h to remove any remaining solvent. It is essential to note that the entire experimental process was carried out meticulously to prevent any impurities from affecting the formation of the intermediate compound. This intermediate compound is a crucial step in the synthesis of the final desired product, which holds significant promise in photocatalytic hydrogen generation. (ii) Holy grain g-C 3 N 4 nanotube preparation : The obtained supra-molecular intermediates were then subjected to a further process to transform them into g-C 3 N 4 nanotubes[ 26 , 44 , 45 ]. To achieve this, the intermediates were placed inside a tubular furnace, and a flow of Ar air was maintained at a rate of 15 mL /min. The furnace was then heated gradually at a temperature rate of 2°C/min until it reached 520°C. The intermediates underwent this heating process for a total duration of 4 h. During this thermal treatment, the supra-molecular intermediates underwent a series of chemical reactions and structural rearrangements facilitated by controlled heating in the presence of Ar gas. As a result, the final product, g-C 3 N 4 nanotubes was formed. These nanotubes possess unique properties and structural characteristics. (iii) Chemical reduction is a crucial method for depositing metal nanoparticles onto semiconductor photocatalysts[ 46 , 47 ]. Various reducing agents such as NaBH 4 , LiBH 4 , N 2 H 4 , LiAlH 4 , etc., are utilized in the reaction solution to facilitate the conversion of metal ions into metal particles, such as the reduction of Ni (II) to Ni (0). It is important to note that this chemical reduction approach does not involve the use of any toxic templates and is conducted at ambient temperature and pressure. A standard chemical reduction procedure for preparing Ni-deposited g-C 3 N 4 heterostructures was as follows: Initially, 0.01 M Nickel (II) nitrate was dissolved in 50 mL of distilled H 2 O and stirred for 5 minutes. Subsequently, 0.2 g of g-C 3 N 4 powder were dispersed into the solution with continuous stirring. To act as a capping and size-controlling agent, 0.001 M PVP was added to the above solution. Next, a freshly prepared solution of the reducing agent, NaBH 4 (0.1 M), was slowly added dropwise to facilitate the reduction of the metal ions. The reduction process was confirmed by observing the colour change of the solution from colourless to black. The stirring continued for 1 hour to ensure complete reduction and deposition of the metal nanoparticles onto the g-C 3 N 4 surface. After the reduction process, the Ni-deposited g-C 3 N 4 heterostructures were collected through centrifugation and washed twice with distilled H 2 O. The resulting precipitate was then dried at 100°C for 4 h to obtain the final Ni/g-C 3 N 4 (shortly, GCNN) composite catalyst. To prepare different molar ratios (0.1, 0.2, 0.3, and 0.4 M) of Ni in the GCNN composites, the volume of Ni precursor was varied while following the same protocol. These samples are denoted as GCNN-1, GCNN-2, GCNN-3, and GCNN-4, respectively. (iv) The described procedure enables the successful and environmentally friendly synthesis of Ni-GCN composite catalysts without the need for toxic templates, and the resulting materials possess potential as hydrogen evolution reaction electrocatalysts[ 48 ]. A standard chemical reduction procedure for preparing Ag-deposited Ni/g-C 3 N 4 heterostructures was as follows[ 49 ]: Initially, 0.01M Silver(I) nitrate was dissolved in 50 mL of distilled H 2 O and stirred for 5 minutes. Subsequently, 0.2 g of Ni/g-C 3 N 4 (GCNN-3) powder were dispersed into the solution with continuous stirring. To act as a capping and size-controlling agent, 0.001 M PVP was added to the above solution. Next, a freshly prepared solution of the reducing agent, NaBH 4 (0.1 M), was slowly added dropwise to facilitate the reduction of the metal ions. The reduction process was confirmed by observing the colour change of the solution from colourless to black. The stirring was continued for 1 h to ensure complete reduction and deposition of the metal nanoparticles onto the g-C 3 N 4 surface. After the reduction process, the Ni/g-C 3 N 4 (GCNN-3) heterostructures were collected through centrifugation and washed twice with distilled H 2 O. The resulting precipitate was then dried at 100°C for 4 h to obtain the final Ag-Ni/g-C 3 N 4 composite catalyst with the detailed mechanism shown in Scheme 1 . To prepare different molar ratios (0.1, 0.2, 0.3, and 0.4 M) of Ag with a 0.3 M of Ni in the Ag-Ni/g-C 3 N 4 (shortly, CAN) composites, the volume of the Ni precursor was varied while following the same protocol. These samples are denoted as CAN-1, CAN-2, CAN-3, and CAN-4, respectively. 2.3 Photocatalytic and Photoelectrochemical Hydrogen Analysis The comprehensive procedures for photocatalytic and photoelectrochemical experiments can be found in the supplementary information section. 2.4 Characterization Instruments Details The complete detail of the characterization equipment can be found in the supplementary information section. 2.5 Computational Details All the DFT results reported in this work were generated using the Vienna ab initio simulation software (VASP)[ 50 ]. The generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional was used to characterize electronic interchange and coherence[ 51 ]. The core electrons were described using the projector augmented wave (PAW) pseudopotentials [ 52 ]. A plane wave basis set was used to describe electron wave functions with a cutoff of 400 eV. Spin-polarization was included in all DFT calculations to describe the magnetic properties. Our XRD analysis confirmed that GCN has a tri-s-triazine structure. We generated a tri-s-triazine model consisting of 24 C atoms and 32 N atoms with a 2 x 2-unit cell along the a and b directions for the DFT calculations ( Figures S9&S10 ). The optimized lattice constant was 7.15 Å, which is consistent with the literature value (7.14 Å)[ 53 ]. The periodic cell contains a vacuum of 15 Å along the c direction to prevent artificial interactions between adjacent layers. We used a 3 × 3 × 1 Monk horst–Pack k-point mesh for all optimization calculations. The reaction energy for H 2 O dissociation was calculated using the total energy difference between the initial and final states. The climbing image-nudged elastic band (CI-NEB)[ 54 ] was used to search for transition states (TS) along the reaction pathway. The activation barrier for H 2 O dissociation was determined through the total energy difference between the initial state and the transition state. The Gibbs free energy of H* adsorption ( \(\varDelta {\text{G}}_{{H}^{\ast }}\) ) was calculated as a descriptor for the hydrogen evolution reaction (HER) using the following equation: \(\varDelta {G}_{{H}^{\ast }}={E}_{{H}^{\ast }+surf}-\left({E}_{surf}+1/2{E}_{{H}_{2}}\right)+\varDelta {E}_{ZPE}-T{\varDelta S}_{H}\) . Here, \({E}_{{H}^{\ast }+surf}\) , \({E}_{surf}\) , and \({E}_{{H}_{2}}\) represent the total energy of an atomic hydrogen adsorbed on the GCN surface, a bare surface, and molecular hydrogen, respectively. \(\varDelta {E}_{ZPE}\) is the difference in the zero-point energy between the adsorbed H and molecular hydrogen. The entropic contribution to the Gibbs free energy, denoted as \(\text{T}\varDelta {S}_{H}\) , was taken from literature as 0.24 eV at 300 K[ 55 ]. 3. Results and Discussion Figure 1 (a-f) shows the construction of a carbon-film liquid cell using two commercially available carbon-coated TEM grids with a film thickness of 10 nm. These grids encapsulate a thin liquid film. To initiate the process, the surface of the carbon films undergoes activation with ozone plasma treatment. Subsequently, a droplet of either a "water-in-salt" LiCl aqueous solution or a pure water solution containing Ag-Ni/g-C 3 N 4 heterostructures is carefully deposited onto one of the carbon films. This is then covered with the second carbon film. As the water droplet evaporates, van der Waals forces come into play, sealing a small quantity of the solution between the two carbon films. For comprehensive details on the synthesis of Ag-Ni/g-C 3 N 4 , the preparation of the "water-in-salt" 3 M LiCl solution, and the fabrication of the liquid cell, please refer to the Experimental Section in the supplementary information. The Ag-Ni/g-C 3 N 4 nanotubes and nanosheets possess dimensions of 90–150 nm in diameter and 900–1000 nm in length[ 56 ]. Notably, the ends of these nanotubes/nanosheets exhibit sharp tips, as seen in Fig. 1 (a-d) . High-resolution images unequivocally confirm their trigonal structure. Moreover, they reveal that the porous nanotubes expose (100) facets on their sides, while the tips are primarily dominated by (002) facets, exemplified in Fig. 1 (f). Static analysis substantiated that all trigonal nanotubes expose {100} facets on their sides and {002} facets at their tips. However, not all of them have {002} facets at the front of their tips, under the influence of a low electron dose rate of 3.6 e-/Å 2 ·s, bubbles can be observed on the sides of the nanorods. Importantly, there are no bubbles present on the tip facets, even when the reaction times are extended up to 30 seconds[ 57 ]. Beyond this 30-second threshold, the density of bubbles diminishes due to the elevated pressure, as explained in further detail in the Electronic Supplementary Information (ESI) ( Figure S2 ). Figure 2 presents a comprehensive morphological structure analysis of the pristine g-C 3 N 4 , and GCNN-3 (Ni/g-C 3 N 4 ). These materials exhibit intricate and diverse porous heterostructures, shedding light on their unique characteristics. The pristine g-C 3 N 4 photocatalyst showcases a porous heterostructure nanoarchitecture (honeycomb nanotube coupled with nanosheets) (Fig. 2 (a-j) ). This complex structure consists of both nanotubes and nano-sheets, introducing a rich variety of morphological features. Within this heterostructure, minute pores or holes are prevalent, measuring approximately 2–3 nanometres. The nanotubes, constituting an integral part of this structure, exhibit diameters ranging from 20 to 30 nm and substantial lengths spanning from 900 to 1000 nanometres. In contrast, the nanosheets within this framework are notably thinner, featuring widths varying between 5 and 10 nm, with corresponding lengths falling within the range of 50 to 70 nm. Upon thorough investigation of GCNN-3, a remarkable nanocomposite formed by combining g-C 3 N 4 and nickel (Ni), and it became evident that the Ni particles were successfully integrated into the carbon nitride hetero structure (Fig. 2 (j-k) ). These Ni particles exhibit a uniform size, typically ranging from 5 to 10 nanometres. This strategic incorporation of Ni particles brings forth a modified structure, one that holds significant potential to influence the properties and catalytic reactivity of the material, which may, in turn, lead to improved performance. In parallel, the g-C 3 N 4 and CAN-2 nanocomposite emerges as a compelling assembly consisting of g-C 3 N 4 , Ni, and silver (Ag) particles and EDAX report (Fig. 2 (l) ). These Ag particles, akin to the Ni counterparts, exhibit a consistent size profile, typically falling within the range of 5 to 10 nm[ 58 ]. The amalgamation of both Ni and Ag particles signifies a significant advancement in the evolution of the original heterostructure, potentially fostering synergistic interactions that can enhance catalytic capabilities and offer promising outcomes in a remarkable impact on photocatalytic hydrogen generation[ 58 , 59 ]. Figure S3-S6 shows the intricate details of the morphological structures within these photocatalysts and their ensuing nanocomposites[ 60 ]. These materials have been meticulously tailored at the nanoscale, endowing them with specific structural attributes and controlled particle sizes. These structural characteristics are pivotal in unravelling and optimizing their photocatalytic potential, making them valuable candidates, and greatly impacting hydrogen generation. In addition, elemental mapping analysis and EDAX of the optimized photocatalyst consist in the C, N, O, Ag, and Ni elements, pristine g-C 3 N 4 existed C, N elements as depicted in Figure S3-S6 . X-ray diffraction (XRD) measurements have had a pivotal role in validating the phase structures of the as-prepared photocatalysts in this study, including g-C 3 N 4 , GCNN-1, GCNN-2, GCNN-3, and GCNN-4. The XRD patterns, thoughtfully presented in Fig. 1 (a), offer a wealth of insights into the crystalline nature of these materials. G-C 3 N 4 , the cornerstone of this investigation, revealed two distinctive diffraction peaks at 27.5° and 13.1°, a signature that unequivocally aligns with the hexagonal phase of polymeric g-C 3 N 4 , as corroborated by the JCPDS reference number #87-1526[ 61 , 62 ]. These peaks hold the key to understanding the atomic arrangement of the material. The robust peak at approximately 27.5° corresponds to the (002) diffraction plane of g-C 3 N 4 , an indication of the interlayer stacking of its aromatic system. In parallel, the fainter peak at around 13.1° arises from the (100) diffraction plane, shedding light on the in-planar s-triazine structural packing motif composed of tris-s-triazine units, with a spacing of approximately 0.73 nm. This comprehensive XRD analysis underscores the crystalline architecture of g-C 3 N 4 , laying the foundation for further exploration (See in Fig. 3 (a) ). Furthermore, when pure Ni metal was deposited onto the g-C 3 N 4 heterostructures (as depicted in Fig. 3 (a) ), a distinct XRD fingerprint emerged. Three primary peaks were observed meticulously centred at approximately 44.5°, 51.85°, and 76.39°. These peaks unambiguously align with the (111), (200), and (220) diffraction planes of hexagonal Ni, in perfect harmony with the JCPDS reference PDF #04-0850[ 59 , 63 , 64 ]. This revelation unveils the crystalline facets of the Ni-metal-g-C 3 N 4 composite. Furthermore, our study encompassed an exploration of optimizing the silver concentration for the GCNN-3 photocatalyst, ranging from 0.1 to 0.4 M. We observed and documented the presence of four significant Ag peaks at 38.08, 44.31, 64.45, and 77.44, which can be attributed to the (111), (200), (220), and (311) crystallographic planes, respectively[ 58 , 65 ]. It is noteworthy that these attributed peaks exhibit exceptional crystallinity and high purity. As we delved deeper into the investigation, we observed a decrease in the peak integration as the silver concentration was increased seen in Fig. 3 (b) . This phenomenon is worth further exploration to gain a comprehensive understanding of its underlying mechanisms. The optical properties of graphitic carbon nitride (g-C 3 N 4 ) were systematically investigated with respect to the optimization of the Ni and Ag concentrations[ 66 ]. UV-vis spectroscopy was used to record and analyse the results, which are presented in Fig. 3 (c-d) . Initially, pure g-C 3 N 4 exhibited an absorption band edge within the range of 450 to 500 nm, with a notable decrease in absorption beyond 450 nm. This characteristic indicated that g-C 3 N 4 had a relatively weak light absorption capacity in the ultraviolet (UV) range but exhibited a significant absorption in the visible region of the electromagnetic spectrum. Upon the introduction of g-C 3 N 4 into the Ag-Ni composite concentration, a remarkable phenomenon was observed in the absorption spectra. Specifically, the absorption band edge exhibited a noticeable red shift, and the visible light absorption capacity within the 450–500 nm range was significantly enhanced. This enhancement had a direct positive impact on the photocatalytic activity of the material. The increased absorption of light was quite evident by the optimized Ni concentration ( Fig. 3 c ) and Ag concentration ( Fig. 3 d ) in the graphitic carbon nitride in the UV-visible light region[ 67 ]. This enhancement in light absorption can be attributed to the interaction occurring within the valence and conduction bands of the Ag-Ni@g-C 3 N 4 composite, thereby facilitating key Schottky barrier heterojunction charge transfer processes[ 38 , 65 , 68 , 69 ]. When compared to other nanocomposite photocatalysts, this composite demonstrated a notably stronger capacity for absorbing visible light. This improvement in visible light absorption served to enhance the overall conversion efficiency of visible light and, consequently, further heightened the photocatalytic activity of the composite material. The optimization of the Ni and Ag concentrations in g-C 3 N 4 , as demonstrated by the spectral data, holds substantial promise for the development of highly efficient photocatalytic materials[ 38 ]. Furthermore, we investigated photocatalytic hydrogen generation and meticulously examined various parameters. Initially, the focal point of the investigation centred on optimizing the concentration of nickel (Ni) in the g-C 3 N4 heterostructures, where four distinct concentrations were considered: GCNN-1 (0.1 M), GCNN-2 (0.2 M), GCNN-3 (0.3 M), and GCNN-4 (0.4 M). Notably, within this array of concentrations, it was evident that GCNN-3 demonstrated superior performance in terms of both the hydrogen production volume and rate, achieving an impressive 638 µmol.h − 1 . g − 1 cat under identical experimental conditions, as seen in Fig. 4 (a-b) [ 70 ]. The observed phenomenon of enhanced hydrogen evolution in GCNN-3, particularly when using a concentration of 0.3 M nickel nanoparticles, can be attributed to several key factors, which are integral to comprehending this noteworthy outcome. (i) Nickel nanoparticles take on the role of co-catalysts. Co-catalysts function in concert with the photocatalyst to facilitate the production of hydrogen. Nickel, in this capacity, has a pivotal role in augmenting the overall photocatalytic activity. It does so by providing active sites conducive to hydrogen evolution and by fostering the separation of charge carriers. (ii) The Schottky effect, a fundamental principle in semiconductor physics, is pertinent here. When a junction is formed between a metal and a semiconductor, such as the amalgamation of nickel nanoparticles with g-C 3 N 4 , it results in the creation of a Schottky barrier. This barrier serves as an enabler of efficient separation of charge carriers, which is indispensable for heightening photocatalytic efficacy. Nickel, functioning as a metal co-catalyst, capitalizes on the Schottky barrier to promote and optimize charge transfer reactions, a fundamental requirement for hydrogen generation. (iii) The concentration of nickel nanoparticles has a pivotal role in fine-tuning the photocatalytic process, at a concentration of 0.3 M, a delicate equilibrium is achieved[ 40 , 71 ]. At this threshold, nickel nanoparticles are instrumental in ensuring the effective adsorption of reactants, encompassing substances like water and other components vital to the hydrogen generation process, onto the surface of the g-C 3 N 4 heterostructure. Simultaneously, this concentration facilitates the rapid and efficient desorption of hydrogen gas once it is generated. This finely tuned balance between adsorption and desorption is critical for achieving an elevated rate of hydrogen evolution. The conspicuous elevation in both the volume and rate of hydrogen generation observed in GCNN-3, specifically when using a concentration of 0.03 M nickel nanoparticles, can be ascribed to the synergistic interplay of nickel as a co-catalyst, the promotion of Schottky charge carrier transfer reactions, and the optimization of adsorption and desorption processes. In addition, we investigated the optimization of the silver (Ag) concentration (CAN-1 (0.1 M), CAN-2 (0.2 M), CAN-3 (0.3 M), and CAN-4 (0.4 M)) on the GCNN-3 (Ni/g-C 3 N 4 ) photocatalyst for improved photocatalytic hydrogen generation. The experimental observation of the CAN-2 catalyst showed a higher rate and volume of photocatalytic hydrogen generation (2507 µmol.h − 1 . g − 1 cat ), due to the optimized silver nanoparticles having exemptional properties such as (i) serving as a photosensitizer, (ii) raising the Plasma resonance effect, and (iii) contributing to the formation of Schottky barriers[ 35 , 67 , 72 – 74 ]. This result extends to the exploration of optimizing the concentration of silver (Ag) in the context of the GCNN-3 photocatalyst to enhance the process of photocatalytic hydrogen generation. Remarkably, the experimental findings indicated that the CAN-2 catalyst exhibited a significantly elevated rate and volume of photocatalytic hydrogen generation, quantified at an impressive 2507 µmol.h − 1 . g − 1 cat (See Fig. 4 (c- d) ). This notable performance can be attributed to the exceptional properties exhibited by the optimized silver nanoparticles, including serving as a photosensitizer, invoking the plasma resonance effect, and contributing to the formation of Schottky barriers. The silver nanoparticles at the optimized concentration of 0.2 M act as potent photosensitizers. In the context of photocatalysis, photosensitizers are materials that enhance the absorption of light by the photocatalyst, which is crucial for driving the catalytic reaction. By sensitizing the photocatalyst, silver nanoparticles make it more responsive to light, thereby increasing the efficiency of hydrogen generation. Silver nanoparticles are renowned for their ability to exhibit the plasma resonance effect. This phenomenon is a result of the collective oscillation of conduction electrons on the surface of the nanoparticles when exposed to specific wavelengths of light. In essence, this resonance effect intensifies the interaction between light and the photocatalyst, enhancing the energy transfer efficiency, thereby promoting higher hydrogen generation rates. Silver nanoparticles contribute to the formation of Schottky barriers when interfaced with the photocatalyst. These barriers have a pivotal role in facilitating the separation of charge carriers. By enabling the efficient separation of these carriers, silver nanoparticles assist in expediting charge transfer reactions, which are a fundamental step in the photocatalytic process of hydrogen production. The experimental findings thus underscore the significance of silver nanoparticles at a concentration of 0.2 M, which not only act as photosensitizers but also invoke the plasma resonance effect and participate in the creation of Schottky barriers. This collective impact results in the remarkable enhancement of the photocatalytic hydrogen generation rate and volume, offering valuable insights for the advancement of sustainable and efficient energy production through photocatalysis. In the ongoing pursuit of refining photocatalytic hydrogen generation, our research focused on optimizing sacrificial reagent concentrations and evaluating the recyclability of the meticulously crafted photocatalyst CAN-2. A pivotal discovery emerged, wherein a sacrificial reagent concentration of 25 vol % stands out as the catalyst for significantly enhanced photocatalytic hydrogen performance, as clearly seen in Fig. 4 (e). The upswing in performance can be traced back to the optimization of the following key factors: improved charge carrier separation, heightened reactant adsorption, and efficient mingling of reactants within the solution. At the core of this advancement lies the superior separation of charge carriers, a fundamental prerequisite for efficient photocatalysis. The orchestrated interplay of electrons and holes, once excited by light, is crucial for driving the redox reactions responsible for hydrogen production. Here, the 25 vol % sacrificial reagent concentration ensures these charge carriers do not prematurely recombine but rather engage in the desired reactions, thus amplifying the rate of hydrogen generation. Furthermore, the influence of this optimized concentration extends to the adsorption of reactants on the surface of the photocatalyst. By enhancing this adsorption process, the reagent concentration guarantees that a surplus of reactants is readily available for the ensuing photocatalytic reactions. This translates into a notable increase in the yield of hydrogen gas, underlining the significance of the 25 vol% threshold[ 64 , 75 ]. Additionally, the meticulous choice of sacrificial reagent concentration optimizes the disruption of the reactant solution, making it a highly effective medium for catalytic interactions. This dynamic interaction, brought about by the concentration selection, enables reactants to efficiently encounter the active sites of the photocatalyst, ensuring that the hydrogen generation process proceeds with remarkable efficiency. Moreover, our research also underscores the robust stability and recyclability of the custom-designed material. As aptly depicted in Fig. 4 (f) , the performance of the material remained exceptional over the course of six cycles, a remarkable testament to its longevity and reliability. This extended performance lifespan holds great promise for real-world applications, where sustained and repeated usage of photocatalysts is a pivotal requirement for practical and efficient hydrogen production processes. The strategic optimization of the sacrificial reagent concentration at 25 vol % yields a substantial boost in photocatalytic hydrogen generation performance by improving the charge carrier separation, reactant adsorption, and reactant solution disruption. Furthermore, the exceptional stability and recyclability of the material across six cycles show its potential for sustainable and enduring use in the quest for clean and efficient hydrogen production[ 76 ]. Figure 5 (a-b) offers comprehensive insight into how the choice of light source impacts the process of photocatalytic hydrogen evolution when using a material that has been meticulously fabricated for optimal performance. Notably, our findings in this context are quite intriguing. One of the most striking observations is that when subject to identical experimental conditions, natural solar light demonstrates significantly superior hydrogen efficiency compared to simulated solar light irradiation. This outcome can be attributed to several key factors. First, natural solar light provides a substantially higher quantity of photoenergy, which fuels the photocatalytic reaction more effectively. Additionally, natural solar light encompasses a broader and richer range of the visible light spectrum when compared to its simulated solar light. This discrepancy in the spectral composition has a pivotal role in enhancing the performance of the photocatalytic process. Figure 5 (a-b) shows the pivotal role the choice of light source has in the efficiency of photocatalytic hydrogen evolution, with natural solar light emerging as the more potent option due to its superior photo energy content and a more extensive visible light spectrum. Figure 5 (c-e) showcases a comprehensive exploration of the photocatalytic hydrogen evolution under various monochromatic light sources, including wavelengths of 365, 400, and 450 nm, and an air mass filter of 1.5 G. Detailed and extensive calculations for the augmented apparent quantum yield efficiency can be found in the electronic supplementary information[ 77 ]. Notably, among the range of monochromatic light sources studied, the 1.5 G air mass filter emerged as the standout performer, exhibiting a remarkable increase in both the rate of hydrogen generation and apparent quantum efficiency. This exceptional performance can be attributed to its lighter intensity and its ability to harness a broader spectrum of visible light. Additionally, a comprehensive assessment involved the calculation of the UV-visible to hydrogen conversion for three distinct photocatalysts: pristine g-C 3 N 4 , GCNN-3, and CAN-2 as shown in Fig. 5 (f) . These results, available in the electronic supplementary information, revealed the following values for the UV-visible to hydrogen conversion: 0.34% for pristine g-C 3 N 4 , an impressive 1.62% for GCNN-3, and a remarkable 6.37% for CAN-2, respectively[ 78 ]. Figure S7 (a-d) and Fig. 6 (e-f) discloses critical insights into the charge carrier recombination and lifetime of the initially synthesized pristine g-C 3 N 4 , GCNN-3, and CAN-2 photocatalysts. The optimized photocatalyst exhibits a notably lower photoluminescence intensity compared to the pristine and GCNN-3 photocatalysts, indicating effective control over charge carrier recombination and photo corrosion in the reaction solution medium. The results highlight the optimized photocatalyst's ability to accomplish these crucial aspects. The investigation extends to the lifetime of the prepared nanohybrids: g-C 3 N 4 -12.9, GCNN-3-84.3, and CAN-2-103.8 ns (refer to Table S2 and Figure S4 (e-f) for detailed information). Photoluminescence spectra are employed to analyse the radiative recombination efficiency of photo-generated charge carriers. Figures S7(a-b) and Fig. 6 (f) depict a distinct reduction in peak intensity in defects-modified g-C 3 N 4 , underscoring the significance of nitrogen defects and surface-active sites in enhancing charge carrier separation efficiency. The peak intensity diminishes with increasing distance (g-C 3 N 4 > GCNN-3 > CAN-2), implicating defects in forming carrier traps that capture carriers and impede recombination. The emission peaks at 625, and 625 nm in the photoluminescence spectra signify band-to-band recombination of holes and electrons, correlating with surface active sites. The research reveals that the defect state and surface-active site’s structure promotes efficient carrier separation, resulting in a low recombination efficiency of photo-excited electron-hole pairs, thereby boosting photocatalytic activity. The active contribution of nitrogen defects and bi metal creates the plenty of surface-active sites for efficient water-splitting events is highlighted, facilitating the movement of charge carriers from the inside to the surface. A study of the charge separation efficiency is a fundamental aspect in the realm of photoelectrochemical systems, and the provided information elucidates the evaluation of this crucial parameter in both pristine g-C 3 N 4 and the optimized CAN-2 (Ag-Ni/g-C 3 N 4 ). Figure 6 (a-c) shows the photocurrent responses of pristine g-C 3 N 4 and the optimized CAN-2 sample under simulated sunlight irradiation. Notably, the data reveals a remarkable enhancement in photocurrent responses over nine consecutive on-off cycles, indicating the stable reproducibility of the results. These cycles reflect the ability of the photoelectrochemical system to repeatedly generate and separate charge carriers efficiently in response to light stimulation. A distinctive behaviour is observed as the photocurrent initiates promptly when the light source is switched on and swiftly decreases to nearly zero when the light is turned off. This behaviour underlines the direct link between the incident light and the generation of the photocurrent, reinforcing the effective utilization of photons for charge separation. Significantly, both the pristine g-C 3 N 4 and optimized CAN-2 exhibit photocurrent densities measured at 1.2 and 5.9 mA/cm 2 , respectively. However, the key observation is that the optimized CAN-2 sample demonstrates a notably stronger photocurrent response. This improvement is attributed to the superior separation efficiency of the photogenerated electron-hole (e − , h + ) pairs in CAN-2, which is further substantiated by its enhanced activity in photocatalytic hydrogen evolution[ 58 ]. Electrochemical impedance spectroscopy (EIS) was used to delve deeper into the charge separation efficiency[ 29 ]. EIS Nyquist plots provide a window into the impedance characteristics of the system, with a smaller semicircle indicating a superior charge separation efficiency. Comparing the EIS Nyquist plot of the pristine g-C 3 N 4 with that of CAN-2, a significant transformation becomes evident (Fig. 6 (d) ). The semicircle representing impedance in the Nyquist plot of g-C 3 N 4 reduces noticeably after the introduction of the Ag-Ni modification. This decrease in impedance indicates a substantial reduction in the recombination of charge carriers, signifying a considerable improvement in the charge separation efficiency. The order of this impedance reduction follows the sequence CAN-2 < g-C 3 N 4 , with CAN-2 exhibiting the most significant enhancement. The reduction in charge carrier recombination serves as a pivotal factor contributing to the superior photoelectrochemical performance of the CAN-2 sample. The enhanced charge separation efficiency in the optimized CAN-2 sample, evident by both the photocurrent response and EIS Nyquist plots, underscores its superior photoelectrochemical performance. This improvement is linked to the reduction in charge carrier recombination, resulting in a more effective separation of photogenerated electron-hole pairs. The findings presented here offer profound insights into the design and optimization of photoelectrochemical systems, with relevance to applications involving photocatalytic hydrogen processes. X-ray Photoelectron Spectroscopy (XPS) measurements were done to gain insights into the composition and electronic structure of the CAN-2 photocatalysts full scan survey spectrum as shown in Figure S8 . Figure 7 (a) reveals the high-resolution XPS spectra of the C 1s peak, deconvoluted into two main peaks at 284.3 and 285.2 eV. These peaks are attributed to the graphitic carbon (C = C) and sp 2 -hybridized carbon found in the N-containing aromatic rings (N-C = N), respectively. Additionally, a new peak at 287.2 eV is observed in the CAN-2 samples, indicating the presence of C-Sp 2 bonds arising from the Ag-Ni particles[ 58 , 80 , 81 ]. In Fig. 7 (b) , the N 1s spectrum shows three distinctive peaks at 398.1 eV (Pyridinic-N), 399.1 eV (Pyrrolic-N), and 400.1 eV (Graphitic-N). However, it is worth noting that the nitrogen-bridging species exhibit a shift in the peak position for CAN-2, suggesting an electron structural change in this sample. In Fig. 7 (c) , the Ni 2p spectrum of the Nickel particles is shown, revealing four critical peaks. Peaks at 872.9 and 855.4 eV correspond to Ni 2p 1/2 and 2p 3/2 , respectively, while satellite peaks at 878.5 and 860.9 eV indicate that Ni primarily exists in the metallic state, with only a minor quantity in the + 2-oxidation state [ 41 , 79 ]. In Fig. 7 (d) , the Ag 3d spectrum highlights two major peaks at 367.7 and 376.2 eV, corresponding to Ag-3d 5/2 and 3d 3/2 . These peaks suggest that Ag atoms are deposited on the triazine rings of the carbon nitride during thermal polymerization. The presence of Ni-Ag atoms likely enhances the electronic density and promotes π-π stacking interactions between the Ag-Ni nanoparticles and conjugated tri-s-triazine units in the polymeric graphitic carbon nitrides[ 58 ]. To assess the specific surface areas of the three samples, nitrogen adsorption-desorption isotherms and pore size distribution were measured (Fig. 7 (e-f) ). Pristine g-C 3 N 4 and CAN-2 photocatalysts exhibit isotherms with an H3-type hysteresis loop, indicative of mesopores. This result aligns with the observed morphology in Fig. 3 d-f. In contrast, CAN-2 exhibits lower N 2 adsorbed volumes, potentially due to a lack of porosity. Pristine g-C 3 N 4 holey grain heterostructures also show poor N 2 adsorption. The specific surface area and pore volume of CAN-2 are 347.2 m 2 /g and 6.8 cm 3 /g, respectively, surpassing those of g-C 3 N 4 , which has a specific surface area of 157.2 m 2 /g and a pore volume of 3.2 cm 3 /g. Comparing CAN-2 with pristine g-C 3 N 4 , it is evident that the optimized photocatalyst boasts a larger surface area and pore volume. This configuration provides more reactive sites and numerous boundaries, which significantly contribute to the photocatalytic process, enhancing the redox reactions and ultimately improving hydrogen efficiency[ 82 ]. To understand the improved hydrogen evolution by Ag blending with Ni nanoparticles, the H 2 O dissociation was calculated using DFT calculations on the Ni/GCN and Ag-Ni/GCN models. Details on the modelling of metal deposited GCN can be found in the electronic supplementary information ( Figures S9&S10 ). On Ni/GCN, H 2 O adsorbs on the top site of Ni with an adsorption energy of ‒0.76 eV shown in Fig. 8 (a) . The OH and H, dissociated from H 2 O, adsorb on the bridge site and 3-fold site, respectively. The H 2 O dissociation process exhibits an activation energy of 1.29 eV and a reaction energy of ‒0.38 eV (Fig. 8 (c) ). On Ag/GCN, it was found that H 2 O preferentially adsorbs on the top site of Ni with an adsorption energy of ‒0.93 eV rather than on the Ag site (Fig. 8 (b) ). The adsorbed H 2 O dissociates into OH and H along the Ni atoms. The activation energy and reaction energy were found to be 0.65 and ‒0.08 eV, respectively. The results show that blending Ag atoms into the Ni particle significantly decreases the activation energy from 1.29 to 0.65 eV, producing more atomic hydrogen on the surface. The Gibbs free energy for the adsorption of atomic hydrogen ( \(\varDelta {G}_{{H}^{\ast }}\) ) is a common activity descriptor for the hydrogen evolution reaction[ 83 ]. An ideal catalyst for the HER exhibits \(\varDelta {G}_{{H}^{\ast }}\) closes to zero. Therefore, the Gibbs free energy for H adsorption was calculated for different sites on Ni/GCN and Ag-Ni /GCN (Fig. 9 (a) ). On Ni/GCN, atomic hydrogen preferentially adsorbs on the Ni-Ni-Ni 3-fold sites. The geometry of the most favourable adsorption in Ni/GCN is shown in Fig. 9 (b) , with a corresponding Gibbs free energy of ‒0.39 eV. The large negative value (‒0.39 eV) indicates that atomic hydrogen binds too strongly to the Ni-Ni-Ni site, preventing the production of molecular hydrogen. On the other hand, bridge sites (Ni-Ni, Ni-Ag, and Ag-Ag) exhibit preferential adsorption of atomic hydrogen on Ni-Ag/GCN, and blending Ag reduces the H adsorption strength. The Ni-Ni site in Ag-Ni /GCN (Fig. 9 (c) ), with a Gibbs free energy of ‒0.20 eV, shows a higher HER activity compared to the Ni-Ni-Ni site in Ag-Ni /GCN. The Gibbs free energy for the Ni-Ag site was 0.01 eV, indicating that it is the optimal site for hydrogen evolution (Fig. 9 (d) ). However, atomic hydrogen binds too weakly on the Ag-Ag site to generate molecular hydrogen (Fig. 9 (e) ), with a Gibbs free energy of 0.33 eV. Overall, these results explain the higher HER activity on Ag-Ni /GCN compared to Ni/GCN. The density of states (DOS) for metal atoms was calculated to analyse the impact of blending Ag on the weakened H adsorption energy. It is known that when the DOS is located further from the Fermi level in the negative direction, the H adsorption strength decreases[ 84 ]. Figure 10 (a-b) shows that the DOS of the Ni atoms shifts downward when mixed with Ag atoms. Furthermore, the DOS of the Ag atoms in Ag-Ni/GCN (CAN-2) is placed at a greater distance from the Fermi level compared to the DOS of the Ni atoms. These findings conclude that Ag atoms diminish the strength of the H adsorption by downwardly shifting the DOS, thereby mitigating the strong interaction between H and Ni. Figure 10 (c) provides insight into the behaviour of the optimized photocatalyst, which was meticulously engineered, with particular attention to its work function and various characterization properties. This photocatalyst, denoted as CAN-2 and consisting of Ag-Ni/g-C 3 N 4 (CAN-2), uses a Schottky barrier charge transfer reaction mechanism (See in Figure S1 ). This mechanism is of paramount importance in enhancing the efficiency of the hydrogen generation. The synergy between the components of the photocatalyst and the Schottky barrier substantially improves the transfer of charge during the hydrogen generation process, resulting in an overall enhanced performance[ 85 ]. The photocatalytic process begins with the illumination of the photocatalyst, which results in the absorption of photon energy. Subsequently, charge carriers, including electrons (e − ) and holes (h + ), are generated within the g-C 3 N 4 hetero-nanostructures. These charge carriers have a pivotal role in the ensuing sequence of reactions. The holes (h+) migrate to the valence band, instigating a crucial step: water oxidation. During this phase, water molecules are cleaved, leading to the release of H + ions, accompanied by the formation of oxidized intermediates. Silver metal has a significant role as a photosensitizer in this process. It acts as a catalyst for the generation of electrons, which are then introduced into the conduction band of the g-C 3 N 4 through a Schottky barrier. This step is vital for the efficient separation of charge carriers and the promotion of electron mobility. Notably, nickel emerges as a co-catalyst, serving to rapidly capture electrons from the conduction band of the g-C 3 N 4 . This function is critical in preventing the undesirable recombination of electrons and holes, ensuring an efficient charge separation process. The captured electrons proceed to react with the generated H + ions. These reactions culminate in the formation of hydrogen gas (H 2 ), a clean and sustainable source of fuel. This intricate photocatalytic system harnesses the power of light to drive the conversion of water into hydrogen fuel, presenting a promising avenue for renewable energy production without relying on conventional, non-renewable resources[ 74 , 86 ]. Conclusions In this ground-breaking investigation, we have achieved a significant breakthrough in the field of photocatalysis by designing and synthesizing a novel hetero-structured Ag-Ni/g-C 3 N 4 material with a unique surface modification configuration. To enhance its photocatalytic performance, we meticulously optimized the concentration of Ag-Ni alloy nanoparticles for surface modification and active site enhancement. Through rigorous physicochemical analyses and the utilization of DFT calculations, we unveiled the pivotal role of graphitic carbon nitride (g-C 3 N 4 ) in facilitating efficient charge transfer and effective separation of photo-generated carriers and visualization hydrogen bubbles by in-situ TEM studies. Notably, the strategic incorporation of Ag-Ni nanoparticles into the g-C 3 N 4 lattice at specific positions led to the formation of the valence band maximum (VBM). Additionally, the hetero microstructure composed of thin g-C 3 N 4 nanotubes coupled with nanosheets has a crucial role in reducing carrier migration distances, thereby effectively suppressing carrier recombination. As a result, this hetero-structured g-C 3 N 4 material not only has an exceptionally high surface area but also provides an abundance of active sites for catalytic reactions. These exceptional characteristics collectively culminated in an outstanding solar light-driven photocatalytic H 2 evolution rate of 2507 µmol h − 1 g − 1 , surpassing the rate achieved by bulk g-C 3 N 4 by an impressive 18.6-fold. Furthermore, the apparent quantum efficiency of this hetero-structured material reached an exceptional value of 1.6% under a 1.5 G air mass filter. Our pioneering work has successfully accompanied in a new era of photocatalysis through the development of this remarkable hetero-structured g-C 3 N 4 material. Its exceptional properties and performance hold great promise for a wide range of applications in harnessing solar energy for catalytic reactions and other advanced technologies. Declarations Acknowledgment This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (MSIT), Dr. V. Navakoteswara Rao gratefully acknowledges the Brain Pool program of MSIT [Project Number 2021H1D3A2A02081839]. This work was also supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (MSIT) (RS-2023-00248428) and ERC Centre funded by the National Research Foundation of Korea (NRF-2022R1A5A1033719). Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐ The authors declare the following financial interests/personal relationships which may be considered as potential competing interests Author Contribution V Navakoteswara Rao, Conceptualization, Investigation, Catalyst fabrication, Software, Formal analysis, Writing-Original Draft, Funding Acquisition.Hyunguk Kwon Investigation Theoretical studies (DFT), Software M Nagaveni, Visualization, Data Curation for photocatalysis P Ravi, Visualization, Data Curation for Photoelectrochemical analysis Yonghee Lee, Investigation, Formal analysis for materials Synthesis Seong Jae Lee, Investigation, Formal analysis for DFT Kyeounghak Kim, Resources, Supervision for DFT analysis M V Shankar, Validation, Manuscript reviewing for photocatalysis hydrogen generationJung Ho Yoo Resources, Supervision for in-situ TEM Chiwon Ahn, Resources, SupervisionSan-jae Kim Writing – Review & Editing, SupervisionJun Mo Yang Conceptualization, Writing, Review & Editing, Supervision, Project Administration, Funding Acquisition. 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J Hazard Mater 125359. https://doi.org/doi.org/10.1016/j.jhazmat.2021.125359 Navakoteswara Rao V, Lakshmana Reddy N, Mamatha Kumari M et al (2019) Photocatalytic recovery of H2 from H2S containing wastewater: Surface and interface control of photo-excitons in Cu2S@TiO2 core-shell nanostructures. Appl Catal B 254:174–185. https://doi.org/https://doi.org/10.1016/j.apcatb.2019.04.090 Song X, Yang Q, Jiang X et al (2017) Porous graphitic carbon nitride nanosheets prepared under self-producing atmosphere for highly improved photocatalytic activity. Appl Catal B 217:322–330. https://doi.org/10.1016/j.apcatb.2017.05.084 Gao D, Liu W, Xu Y et al (2020) Core-shell Ag@Ni cocatalyst on the TiO2 photocatalyst: One-step photoinduced deposition and its improved H2-evolution activity. Appl Catal B 260. https://doi.org/10.1016/j.apcatb.2019.118190 An H, Xiao S, Zhao X et al (2021) Construction of Highly Efficient Photocatalyst with Core-Shell Au@Ag/C@SiO2 Hybrid Structure towards Visible-Light-Driven Photocatalytic Reduction. Chin J Chem 39:2865–2872. https://doi.org/10.1002/cjoc.202100167 Wang Y, Meng D, Zhao X (2020) Visible-light-driven H2O2 production from O2 reduction with nitrogen vacancy-rich and porous graphitic carbon nitride. Appl Catal B 273:119064. https://doi.org/10.1016/j.apcatb.2020.119064 Greeley J, Jaramillo TF, Bonde J et al (2006) Computational high-throughput screening of electrocatalytic materials for hydrogen evolution. Nat Mater 5:909–913. https://doi.org/10.1038/nmat1752 Kitchin JR, Nørskov JK, Barteau MA, Chen JG (2005) Trends in the chemical properties of early transition metal carbide surfaces: A density functional study. Catal Today 105:66–73. https://doi.org/10.1016/j.cattod.2005.04.008 Huang K, Li C, Zhang X et al (2021) Self-assembly synthesis of phosphorus-doped tubular g-C3N4/Ti3C2 MXene Schottky junction for boosting photocatalytic hydrogen evolution. Green Energy Environ. https://doi.org/10.1016/j.gee.2021.03.011 Sherryna A, Tahir M (2021) Role of Ti3C2MXene as Prominent Schottky Barriers in Driving Hydrogen Production through Photoinduced Water Splitting: A Comprehensive Review. ACS Appl Energy Mater 4:11982–12006 Scheme Scheme 1 is available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files 02.ESIrevised.docx floatimage1.png Scheme 1 Pictorial representation of the preparation Ag-Ni/g-C 3 N 4 (CAN-2) heterostructures. 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03:31:50","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3971500/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3971500/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":52424451,"identity":"6ae93994-ff9e-49ba-b697-06483e81be16","added_by":"auto","created_at":"2024-03-11 13:18:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":818266,"visible":true,"origin":"","legend":"\u003cp\u003eReal-time analysis of hydrogen bubble generation under electron beam irradiation (3.6 e\u003csup\u003e-\u003c/sup\u003e/A\u003csup\u003e2\u003c/sup\u003e) at different time intervals (a) 4, (b) 8, (c) 16, (d) 20, (e) 25, and (f) 30 s (CAN-2 photocatalyst).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/1720333c1bae5c0b06fe13bd.png"},{"id":52424155,"identity":"f22bc0e0-1773-4139-8b29-34b97e6609c9","added_by":"auto","created_at":"2024-03-11 13:10:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2482792,"visible":true,"origin":"","legend":"\u003cp\u003e(a-f)\u003cstrong\u003e \u003c/strong\u003eFE-SEM images of the porous heterostructure holey grain nanotubes/nanosheets of the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4, \u003c/sub\u003e(g-i)\u003csub\u003e \u003c/sub\u003eMorphology structure analysis of Pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4, \u003c/sub\u003e(j-k) GCNN-3, (l) CAN-2 photocatalyst.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/d8a418f23165636c0593663f.png"},{"id":52424158,"identity":"493b5b00-49b3-448f-bfa3-88faa64dd29a","added_by":"auto","created_at":"2024-03-11 13:10:23","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1385987,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of the (a) g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (GCNN-1 to GCNN-4) with different Ni ratios, (b) XRD patterns of the Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (CAN-1 to CAN-4) with different Ag ratios. (c) The optical absorption spectra of pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4 \u003c/sub\u003eand Ni deposited g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with different Ni concentration (GCNN-1 to GCNN-4). (d) Optimization of the silver concentration on the Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e photocatalyst (CAN-1 to CAN-4).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/c49a43991f538ea60023c548.png"},{"id":52424157,"identity":"ae638f73-0f01-4c44-b109-3a83d47ecfde","added_by":"auto","created_at":"2024-03-11 13:10:23","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":784739,"visible":true,"origin":"","legend":"\u003cp\u003e(a)\u003cstrong\u003e \u003c/strong\u003eVolumetric and rate of photocatalytic hydrogen generation evolution on Ni deposited g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with different Ni ratios and (b-c) Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with different Ag ratios.\u0026nbsp; (e) Optimization of the sacrificial reagent concentration. (f) Recyclability of the optimized photocatalyst up to 6 cycles.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/63bb9e64caed6e1415649acb.png"},{"id":52424165,"identity":"90396768-6038-4bd4-bc37-a9d7ea6171ed","added_by":"auto","created_at":"2024-03-11 13:10:23","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":670576,"visible":true,"origin":"","legend":"\u003cp\u003ePhotocatalytic parametric studies. Effect of light sources on the (a) volume and (b) rate of hydrogen generation. Effect of monochromatic lights on the (c) volume and (d) rate of the photocatalytic hydrogen generation and (e) apparent quantum efficiency (APQY) at 365, 400, 450, 1.5 G air mass filter. (f) UV visible to hydrogen (UTH) conversion efficiency from UV-visible light irradiation.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/7ea15f9ae75a04c7993b474e.png"},{"id":52424159,"identity":"7de7af31-ced7-45bf-ad5d-b562ecbc08c3","added_by":"auto","created_at":"2024-03-11 13:10:23","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":649090,"visible":true,"origin":"","legend":"\u003cp\u003e(a-b) Photocurrent measurements of the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and CAN-2 photocatalysts up to 9 cycles, (c) Stability of the optimized CAN-2 photocatalyst, (d) Electronic Impendence spectrum of the pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and CAN-2 photocatalysts. (e) Photolumiscience of the CAN-2 photocatalyst, (f) Time Resolved photoluminescence spectrum of the CAN-2 photocatalyst. \u0026nbsp;\u0026nbsp;\u0026nbsp;\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/f0816c2052fb92ff305a8cec.png"},{"id":52424161,"identity":"d98e11a7-7ebb-430f-a027-bcd3ba5b40b3","added_by":"auto","created_at":"2024-03-11 13:10:23","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":905432,"visible":true,"origin":"","legend":"\u003cp\u003eValence state analysis of the CAN-2 photocatalyst spectrum (a) C-1S, (b) N, (c) Ni-2p, and (d) Ag-3d, and (e-f) BET Surface area of the pure g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and CAN-2 heterostructure materials.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/7b21f0faee5faa85ecd91117.png"},{"id":52424163,"identity":"164f7a8f-4187-4687-b220-4159abc9c436","added_by":"auto","created_at":"2024-03-11 13:10:23","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":415471,"visible":true,"origin":"","legend":"\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO dissociation on (a) Ni/GCN (GCNN-3) and (b) Ag-Ni/GCN (CAN-2). (c) The reaction diagram for the H\u003csub\u003e2\u003c/sub\u003eO dissociation.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/d0b944c3b8f388d8c4cb3967.png"},{"id":52424460,"identity":"3991a47f-5a1e-4551-8ce5-b4f2c7a91393","added_by":"auto","created_at":"2024-03-11 13:18:23","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":366723,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The Gibbs free energy of the hydrogen evolution reaction corresponding to (b) through (e). (b) shows the strongest adsorption in Ni/GCN. (c), (d), and (e) represent the most favourable adsorption among the Ni-Ni sites, Ni-Ag sites, and Ag-Ag sites, respectively, on Ag-Ni /GCN.\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/194facee1b2b529d624f1bf9.png"},{"id":52424461,"identity":"78816c5f-0107-455f-a955-a8215886b2d1","added_by":"auto","created_at":"2024-03-11 13:18:23","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":1214662,"visible":true,"origin":"","legend":"\u003cp\u003eThe density of states for the metal atoms in (a) Ni/GCN and (b) Ag-Ni /GCN (CAN-2). The dotted vertical line indicates the d-band centre. (c) Pictorial representation of the Schottky charge transfer reaction mechanism of the optimized CAN-2 photocatalyst.\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/9286d1f34cedc1199b670e14.png"},{"id":54603881,"identity":"76c82199-96a9-491d-b675-3dba700d442e","added_by":"auto","created_at":"2024-04-13 01:22:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6640410,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/5856f5de-0647-4525-a917-36b541da2358.pdf"},{"id":52424166,"identity":"0ac15190-b873-48b5-be1e-1cf3fc23b6c1","added_by":"auto","created_at":"2024-03-11 13:10:23","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":7140296,"visible":true,"origin":"","legend":"","description":"","filename":"02.ESIrevised.docx","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/e3c23a46e4fb52bae14cb769.docx"},{"id":52424160,"identity":"a42a2e0c-87ba-42ec-85fa-d0ba8be61e72","added_by":"auto","created_at":"2024-03-11 13:10:23","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":1166444,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScheme 1 \u003c/strong\u003ePictorial representation of the preparation Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e(CAN-2) heterostructures.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3971500/v1/6433c41cb503f6780e5e0deb.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Tailoring Schottky Barriers and Active Sites in Bi-metallic Cluster Mesoporous Carbon Nitride Heterostructures nanocomposite for Hydrogen Evolution with In-situ insights","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIn recent decades, the world has been confronted with an unparalleled challenge in the form of an energy crisis brought by the surging global population and rapid industrialization. Our growing energy demands have predominantly relied on non-renewable resources like coal, fossil fuels, petrol, and oil, leading to their alarming depletion[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Disturbingly, projections indicate that by 2050, the world's energy requirements will surpass twice the capacity of existing energy supplies[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Beyond depletion, the utilization of these non-renewable sources has inflicted grave damage upon the environment with greenhouse gas emissions being a major concern. It is evident that we need a transformative solution, and renewable energy sources have emerged as the most promising alternative to address these pressing issues. For example, there are many eco-friendly options, including hydroelectricity, biomass, wind, geothermal energy, and solar light that include applications like solar drying and solar cooking[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. One particularly ingenious approach to alleviating the impending energy crisis and environmental degradation lies in harnessing the power of solar energy through photosynthesis[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. By converting solar energy into chemical energy, we can produce environmentally friendly hydrogen gas, which upon consumption, only yields water or water vapours, leaving no harmful traces behind[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Embracing this innovative method not only enables us to meet the future energy demand sustainably but also has a crucial role in safeguarding our planet's fragile ecosystem[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The potential of solar energy harvesting to produce clean hydrogen gas offers a beacon of hope for a greener and more sustainable future[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. As we strive toward a world driven by renewable resources, we pave the path to tackle the energy crisis while upholding our responsibility to protect the environment for evolution[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHydrogen, with its impressive heat value of 120\u0026ndash;142 MJ kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, is widely recognized as a clean and efficient source of solar energy. Recently, the global production of hydrogen has exceeded 44.5\u0026nbsp;million tons, and its prominence as a primary energy source is projected to endure until 2080[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Amidst the various methods of hydrogen production, photocatalytic water splitting shines as a promising approach, captivating considerable attention for its diverse potential in both environmental and energy applications[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Artificial photosynthesis, a revolutionary concept, has emerged as one of the most environmentally friendly solutions to tackle the impending crises in energy and the environment[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. By emulating the natural process of photosynthesis, this innovative technique harnesses the power of sunlight to facilitate the conversion of water into hydrogen gas[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Not only does this method hold tremendous promise in addressing the world's energy needs, but it also offers an elegant and sustainable means to mitigate environmental challenges[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The journey towards a greener and more sustainable future heavily relies on pioneering approaches like photocatalytic water splitting and artificial photosynthesis. By tapping into these cutting-edge technologies, we pave the way for a harmonious coexistence with our planet, ensuring a brighter and cleaner tomorrow for future generations[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eGraphitic carbon nitride (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) has gained prominence as an efficient photocatalyst due to its remarkable properties[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. First, it exhibits visible light absorption with a bandgap ranging from 2.6 to 2.7 eV, enabling it to harness a substantial portion of the solar spectrum for photocatalytic reactions. Moreover, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e demonstrates excellent stability under photocatalytic conditions, ensuring long-term use without significant degradation. Its large specific surface area offers abundant active sites, enhancing its catalytic efficiency[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. These tuneable properties make it versatile, enabling customized materials for specific applications. Furthermore, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e is environmentally friendly, composed of earth-abundant elements like carbon and nitrogen unlike catalysts based on rare or toxic elements[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Photocatalytic activity is a benchmark of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, participating in reactions like water splitting, pollutant degradation, CO\u003csub\u003e2\u003c/sub\u003e reduction, and organic synthesis, making it valuable for sustainable energy conversion and environmental remediation[\u003cspan additionalcitationids=\"CR28\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Lastly, it boasts cost-effectiveness, as the raw materials for its synthesis are readily available and inexpensive. Due to these attributes, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e is widely studied for its potential in various applications[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe addition of a bimetallic catalyst, typically composed of a photosensitizer (e.g., Ag, Au, and Ni) and a co-catalyst, further enhances its photocatalytic efficiency[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The photosensitizer broadens the light absorption range, including visible light, improving electron-hole pair generation[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Effective charge carrier separation is crucial because recombination diminishes photocatalytic activity[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. The co-catalyst acts as an electron trap, capturing electrons and preventing their recombination with holes. It also boosts catalytic activity by facilitating reduction reactions, such as hydrogen evolution during photocatalytic water splitting. This dual catalyst system enhances hydrogen generation rates and efficiency while improving stability and addresses potential degradation issues during prolonged exposure to light and reaction conditions[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Harnessing solar energy for hydrogen generation reduces reliance on fossil fuels and mitigates climate change. The dual (Ag-Ni) catalyst enhances photocatalytic efficiency, significantly reducing the energy consumption required for hydrogen production and thereby promoting a sustainable and eco-friendly approach[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. To the best of our knowledge, there is no existing literature on the fabrication of holey grain nanotubes with dual-catalyst deposition for photocatalytic hydrogen generation. Exploring holey grain nanotubes combined with dual co-catalysts has the potential to significantly enhance photocatalytic surface medication properties and active sites[\u003cspan additionalcitationids=\"CR40\" citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this study, we developed a straightforward and efficient synthesis process to create holey grain g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nanotubes/nanosheets heterostructure and successfully incorporated them into a dual catalyst (Ni-Ag) for enhanced hydrogen production. Our optimized photocatalyst demonstrated a remarkable hydrogen generation rate when exposed to simulated solar light irradiation shown by in situ TEM analysis. Notably, the apparent quantum yield and overall UTH (UV-visible-to-hydrogen) conversion efficiency show exceptional performance. To support our findings, we performed density functional theory (DFT) calculations, and the results obtained from our experiments align closely with the theoretical predictions. This synergy between experimental results and theoretical modelling underscores the robustness of our approach and the potential for significant advancements in photocatalytic hydrogen production efficiency.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Reagents and Solvents\u003c/h2\u003e\n \u003cp\u003eAll chemicals were of analytical grade and used without further purification or distillation steps unless otherwise noted: hydroxylamine sulphate (NH\u003csub\u003e4\u003c/sub\u003eOH.H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4,\u003c/sub\u003e Sigma Aldrich, 99%), melamine (C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e(NH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e, Sigma Aldrich, 99%), Nickel (II) nitrate (Ni(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, Sigma Aldrich, 99%), NaBH\u003csub\u003e4\u003c/sub\u003e (Fisher Scientific, 99%), Poly Vinyl pyrrolidine (PVP, Merck, 99%), Na\u003csub\u003e2\u003c/sub\u003eSo\u003csub\u003e4\u003c/sub\u003e (Sigma Aldrich, 99%), HCl (Sigma Aldrich, 99%), NaOH (Sigma Aldrich, 99%), Nafion solution (Fisher Scientific, 99%), and ethanol (C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eOH, Merck, 99.9%). Both ultra-pure water (H\u003csub\u003e2\u003c/sub\u003eO) was utilized for the photocatalytic hydrogen (H\u003csub\u003e2\u003c/sub\u003e) evolution experiments.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Experiments\u003c/h2\u003e\n \u003cp\u003e\u003cem\u003e(i) The complex Intermediate preparation\u003c/em\u003e: In this experimental procedure, we utilized typical hydrothermal processes to synthesize an intermediate compound[\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e]. The process began with the dispersion of 2 g of hydroxylamine sulphate (NH\u003csub\u003e4\u003c/sub\u003eOH.H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e) and 1 g of melamine (C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e(NH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e) into 35 mL of deionized water. Both precursors were mixed using magnetic stirring for a duration of 30 min. Subsequently, the mixture was carefully transferred into a 50 mL Teflon-lined autoclave and heated to 120\u0026deg;C for a period of 12 h. After the hydrothermal reaction was completed, the resulting product was collected in 50 mL beakers and underwent a series of washing steps. The washing was performed alternately with deionized water and absolute ethanol, repeating the process five times to ensure purity. Finally, the synthesized intermediate compound was dried at 80\u0026deg;C for 12 h to remove any remaining solvent. It is essential to note that the entire experimental process was carried out meticulously to prevent any impurities from affecting the formation of the intermediate compound. This intermediate compound is a crucial step in the synthesis of the final desired product, which holds significant promise in photocatalytic hydrogen generation.\u003c/p\u003e\u003cspan\u003e\n \u003cp\u003e\u003cem\u003e(ii) Holy grain g-C\u003c/em\u003e \u003csub\u003e\u0026nbsp;\u003cem\u003e3\u003c/em\u003e\u0026nbsp;\u003c/sub\u003e \u003cem\u003eN\u003c/em\u003e \u003csub\u003e\u0026nbsp;\u003cem\u003e4\u003c/em\u003e\u0026nbsp;\u003c/sub\u003e \u003cem\u003enanotube preparation\u003c/em\u003e: The obtained supra-molecular intermediates were then subjected to a further process to transform them into g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nanotubes[\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e]. To achieve this, the intermediates were placed inside a tubular furnace, and a flow of Ar air was maintained at a rate of 15 mL /min. The furnace was then heated gradually at a temperature rate of 2\u0026deg;C/min until it reached 520\u0026deg;C. The intermediates underwent this heating process for a total duration of 4 h. During this thermal treatment, the supra-molecular intermediates underwent a series of chemical reactions and structural rearrangements facilitated by controlled heating in the presence of Ar gas. As a result, the final product, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nanotubes was formed. These nanotubes possess unique properties and structural characteristics.\u003c/p\u003e\n \u003c/span\u003e \u003cspan\u003e\n \u003cp\u003e(iii) Chemical reduction is a crucial method for depositing metal nanoparticles onto semiconductor photocatalysts[\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e]. Various reducing agents such as NaBH\u003csub\u003e4\u003c/sub\u003e, LiBH\u003csub\u003e4\u003c/sub\u003e, N\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e4\u003c/sub\u003e, LiAlH\u003csub\u003e4\u003c/sub\u003e, etc., are utilized in the reaction solution to facilitate the conversion of metal ions into metal particles, such as the reduction of Ni (II) to Ni (0). It is important to note that this chemical reduction approach does not involve the use of any toxic templates and is conducted at ambient temperature and pressure.\u003c/p\u003e\n \u003c/span\u003e\n \u003cp\u003eA standard chemical reduction procedure for preparing Ni-deposited g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e heterostructures was as follows: Initially, 0.01 M Nickel (II) nitrate was dissolved in 50 mL of distilled H\u003csub\u003e2\u003c/sub\u003eO and stirred for 5 minutes. Subsequently, 0.2 g of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e powder were dispersed into the solution with continuous stirring. To act as a capping and size-controlling agent, 0.001 M PVP was added to the above solution. Next, a freshly prepared solution of the reducing agent, NaBH\u003csub\u003e4\u003c/sub\u003e (0.1 M), was slowly added dropwise to facilitate the reduction of the metal ions. The reduction process was confirmed by observing the colour change of the solution from colourless to black. The stirring continued for 1 hour to ensure complete reduction and deposition of the metal nanoparticles onto the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e surface. After the reduction process, the Ni-deposited g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e heterostructures were collected through centrifugation and washed twice with distilled H\u003csub\u003e2\u003c/sub\u003eO. The resulting precipitate was then dried at 100\u0026deg;C for 4 h to obtain the final Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (shortly, GCNN) composite catalyst. To prepare different molar ratios (0.1, 0.2, 0.3, and 0.4 M) of Ni in the GCNN composites, the volume of Ni precursor was varied while following the same protocol. These samples are denoted as GCNN-1, GCNN-2, GCNN-3, and GCNN-4, respectively.\u003c/p\u003e\n \u003cp\u003e(iv) The described procedure enables the successful and environmentally friendly synthesis of Ni-GCN composite catalysts without the need for toxic templates, and the resulting materials possess potential as hydrogen evolution reaction electrocatalysts[\u003cspan class=\"CitationRef\"\u003e48\u003c/span\u003e]. A standard chemical reduction procedure for preparing Ag-deposited Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e heterostructures was as follows[\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e]: Initially, 0.01M Silver(I) nitrate was dissolved in 50 mL of distilled H\u003csub\u003e2\u003c/sub\u003eO and stirred for 5 minutes. Subsequently, 0.2 g of Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (GCNN-3) powder were dispersed into the solution with continuous stirring. To act as a capping and size-controlling agent, 0.001 M PVP was added to the above solution. Next, a freshly prepared solution of the reducing agent, NaBH\u003csub\u003e4\u003c/sub\u003e (0.1 M), was slowly added dropwise to facilitate the reduction of the metal ions. The reduction process was confirmed by observing the colour change of the solution from colourless to black. The stirring was continued for 1 h to ensure complete reduction and deposition of the metal nanoparticles onto the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e surface. After the reduction process, the Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (GCNN-3) heterostructures were collected through centrifugation and washed twice with distilled H\u003csub\u003e2\u003c/sub\u003eO. The resulting precipitate was then dried at 100\u0026deg;C for 4 h to obtain the final Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e composite catalyst with the detailed mechanism shown in Scheme \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. To prepare different molar ratios (0.1, 0.2, 0.3, and 0.4 M) of Ag with a 0.3 M of Ni in the Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (shortly, CAN) composites, the volume of the Ni precursor was varied while following the same protocol. These samples are denoted as CAN-1, CAN-2, CAN-3, and CAN-4, respectively.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Photocatalytic and Photoelectrochemical Hydrogen Analysis\u003c/h2\u003e\n \u003cp\u003eThe comprehensive procedures for photocatalytic and photoelectrochemical experiments can be found in the supplementary information section.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Characterization Instruments Details\u003c/h2\u003e\n \u003cp\u003eThe complete detail of the characterization equipment can be found in the supplementary information section.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e2.5 Computational Details\u003c/h2\u003e\n \u003cp\u003eAll the DFT results reported in this work were generated using the Vienna ab initio simulation software (VASP)[\u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e]. The generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional was used to characterize electronic interchange and coherence[\u003cspan class=\"CitationRef\"\u003e51\u003c/span\u003e]. The core electrons were described using the projector augmented wave (PAW) pseudopotentials [\u003cspan class=\"CitationRef\"\u003e52\u003c/span\u003e]. A plane wave basis set was used to describe electron wave functions with a cutoff of 400 eV. Spin-polarization was included in all DFT calculations to describe the magnetic properties.\u003c/p\u003e\n \u003cp\u003eOur XRD analysis confirmed that GCN has a tri-s-triazine structure. We generated a tri-s-triazine model consisting of 24 C atoms and 32 N atoms with a 2 x 2-unit cell along the \u003cem\u003ea\u003c/em\u003e and \u003cem\u003eb\u003c/em\u003e directions for the DFT calculations (\u003cstrong\u003eFigures S9\u0026amp;S10\u003c/strong\u003e). The optimized lattice constant was 7.15 \u0026Aring;, which is consistent with the literature value (7.14 \u0026Aring;)[\u003cspan class=\"CitationRef\"\u003e53\u003c/span\u003e]. The periodic cell contains a vacuum of 15 \u0026Aring; along the \u003cem\u003ec\u003c/em\u003e direction to prevent artificial interactions between adjacent layers. We used a 3 \u0026times; 3 \u0026times; 1 Monk horst\u0026ndash;Pack k-point mesh for all optimization calculations.\u003c/p\u003e\n \u003cp\u003eThe reaction energy for H\u003csub\u003e2\u003c/sub\u003eO dissociation was calculated using the total energy difference between the initial and final states. The climbing image-nudged elastic band (CI-NEB)[\u003cspan class=\"CitationRef\"\u003e54\u003c/span\u003e] was used to search for transition states (TS) along the reaction pathway. The activation barrier for H\u003csub\u003e2\u003c/sub\u003eO dissociation was determined through the total energy difference between the initial state and the transition state. The Gibbs free energy of H* adsorption (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varDelta {\\text{G}}_{{H}^{\\ast }}\\)\u003c/span\u003e\u003c/span\u003e) was calculated as a descriptor for the hydrogen evolution reaction (HER) using the following equation: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varDelta {G}_{{H}^{\\ast }}={E}_{{H}^{\\ast }+surf}-\\left({E}_{surf}+1/2{E}_{{H}_{2}}\\right)+\\varDelta {E}_{ZPE}-T{\\varDelta S}_{H}\\)\u003c/span\u003e\u003c/span\u003e. Here, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({E}_{{H}^{\\ast }+surf}\\)\u003c/span\u003e\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({E}_{surf}\\)\u003c/span\u003e\u003c/span\u003e, and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({E}_{{H}_{2}}\\)\u003c/span\u003e\u003c/span\u003e represent the total energy of an atomic hydrogen adsorbed on the GCN surface, a bare surface, and molecular hydrogen, respectively. \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varDelta {E}_{ZPE}\\)\u003c/span\u003e\u003c/span\u003e is the difference in the zero-point energy between the adsorbed H and molecular hydrogen. The entropic contribution to the Gibbs free energy, denoted as \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{T}\\varDelta {S}_{H}\\)\u003c/span\u003e\u003c/span\u003e, was taken from literature as 0.24 eV at 300 K[\u003cspan class=\"CitationRef\"\u003e55\u003c/span\u003e].\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(a-f)\u003c/b\u003e shows the construction of a carbon-film liquid cell using two commercially available carbon-coated TEM grids with a film thickness of 10 nm. These grids encapsulate a thin liquid film. To initiate the process, the surface of the carbon films undergoes activation with ozone plasma treatment. Subsequently, a droplet of either a \"water-in-salt\" LiCl aqueous solution or a pure water solution containing Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e heterostructures is carefully deposited onto one of the carbon films. This is then covered with the second carbon film. As the water droplet evaporates, van der Waals forces come into play, sealing a small quantity of the solution between the two carbon films. For comprehensive details on the synthesis of Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, the preparation of the \"water-in-salt\" 3 M LiCl solution, and the fabrication of the liquid cell, please refer to the Experimental Section in the supplementary information. The Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nanotubes and nanosheets possess dimensions of 90–150 nm in diameter and 900–1000 nm in length[\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. Notably, the ends of these nanotubes/nanosheets exhibit sharp tips, as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(a-d)\u003c/b\u003e. High-resolution images unequivocally confirm their trigonal structure. Moreover, they reveal that the porous nanotubes expose (100) facets on their sides, while the tips are primarily dominated by (002) facets, exemplified in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(f).\u003c/b\u003e Static analysis substantiated that all trigonal nanotubes expose {100} facets on their sides and {002} facets at their tips. However, not all of them have {002} facets at the front of their tips, under the influence of a low electron dose rate of 3.6 e-/Å\u003csup\u003e2\u003c/sup\u003e·s, bubbles can be observed on the sides of the nanorods. Importantly, there are no bubbles present on the tip facets, even when the reaction times are extended up to 30 seconds[\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e]. Beyond this 30-second threshold, the density of bubbles diminishes due to the elevated pressure, as explained in further detail in the Electronic Supplementary Information (ESI) (\u003cb\u003eFigure S2\u003c/b\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents a comprehensive morphological structure analysis of the pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, and GCNN-3 (Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e). These materials exhibit intricate and diverse porous heterostructures, shedding light on their unique characteristics. The pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e photocatalyst showcases a porous heterostructure nanoarchitecture (honeycomb nanotube coupled with nanosheets) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(a-j)\u003c/b\u003e). This complex structure consists of both nanotubes and nano-sheets, introducing a rich variety of morphological features. Within this heterostructure, minute pores or holes are prevalent, measuring approximately 2–3 nanometres. The nanotubes, constituting an integral part of this structure, exhibit diameters ranging from 20 to 30 nm and substantial lengths spanning from 900 to 1000 nanometres. In contrast, the nanosheets within this framework are notably thinner, featuring widths varying between 5 and 10 nm, with corresponding lengths falling within the range of 50 to 70 nm. Upon thorough investigation of GCNN-3, a remarkable nanocomposite formed by combining g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and nickel (Ni), and it became evident that the Ni particles were successfully integrated into the carbon nitride hetero structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(j-k)\u003c/b\u003e). These Ni particles exhibit a uniform size, typically ranging from 5 to 10 nanometres. This strategic incorporation of Ni particles brings forth a modified structure, one that holds significant potential to influence the properties and catalytic reactivity of the material, which may, in turn, lead to improved performance. In parallel, the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and CAN-2 nanocomposite emerges as a compelling assembly consisting of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, Ni, and silver (Ag) particles and EDAX report (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(l)\u003c/b\u003e). These Ag particles, akin to the Ni counterparts, exhibit a consistent size profile, typically falling within the range of 5 to 10 nm[\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. The amalgamation of both Ni and Ag particles signifies a significant advancement in the evolution of the original heterostructure, potentially fostering synergistic interactions that can enhance catalytic capabilities and offer promising outcomes in a remarkable impact on photocatalytic hydrogen generation[\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e]. \u003cb\u003eFigure S3-S6\u003c/b\u003e shows the intricate details of the morphological structures within these photocatalysts and their ensuing nanocomposites[\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. These materials have been meticulously tailored at the nanoscale, endowing them with specific structural attributes and controlled particle sizes. These structural characteristics are pivotal in unravelling and optimizing their photocatalytic potential, making them valuable candidates, and greatly impacting hydrogen generation. In addition, elemental mapping analysis and EDAX of the optimized photocatalyst consist in the C, N, O, Ag, and Ni elements, pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e existed C, N elements as depicted in \u003cb\u003eFigure S3-S6\u003c/b\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eX-ray diffraction (XRD) measurements have had a pivotal role in validating the phase structures of the as-prepared photocatalysts in this study, including g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, GCNN-1, GCNN-2, GCNN-3, and GCNN-4. The XRD patterns, thoughtfully presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a), offer a wealth of insights into the crystalline nature of these materials. G-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, the cornerstone of this investigation, revealed two distinctive diffraction peaks at 27.5° and 13.1°, a signature that unequivocally aligns with the hexagonal phase of polymeric g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, as corroborated by the JCPDS reference number #87-1526[\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e]. These peaks hold the key to understanding the atomic arrangement of the material. The robust peak at approximately 27.5° corresponds to the (002) diffraction plane of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, an indication of the interlayer stacking of its aromatic system. In parallel, the fainter peak at around 13.1° arises from the (100) diffraction plane, shedding light on the in-planar s-triazine structural packing motif composed of tris-s-triazine units, with a spacing of approximately 0.73 nm. This comprehensive XRD analysis underscores the crystalline architecture of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, laying the foundation for further exploration (See in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFurthermore, when pure Ni metal was deposited onto the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e heterostructures (as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e), a distinct XRD fingerprint emerged. Three primary peaks were observed meticulously centred at approximately 44.5°, 51.85°, and 76.39°. These peaks unambiguously align with the (111), (200), and (220) diffraction planes of hexagonal Ni, in perfect harmony with the JCPDS reference PDF #04-0850[\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e, \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e, \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e]. This revelation unveils the crystalline facets of the Ni-metal-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e composite. Furthermore, our study encompassed an exploration of optimizing the silver concentration for the GCNN-3 photocatalyst, ranging from 0.1 to 0.4 M. We observed and documented the presence of four significant Ag peaks at 38.08, 44.31, 64.45, and 77.44, which can be attributed to the (111), (200), (220), and (311) crystallographic planes, respectively[\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e]. It is noteworthy that these attributed peaks exhibit exceptional crystallinity and high purity. As we delved deeper into the investigation, we observed a decrease in the peak integration as the silver concentration was increased seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e. This phenomenon is worth further exploration to gain a comprehensive understanding of its underlying mechanisms. The optical properties of graphitic carbon nitride (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) were systematically investigated with respect to the optimization of the Ni and Ag concentrations[\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e]. UV-vis spectroscopy was used to record and analyse the results, which are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e(c-d)\u003c/b\u003e. Initially, pure g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e exhibited an absorption band edge within the range of 450 to 500 nm, with a notable decrease in absorption beyond 450 nm. This characteristic indicated that g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e had a relatively weak light absorption capacity in the ultraviolet (UV) range but exhibited a significant absorption in the visible region of the electromagnetic spectrum. Upon the introduction of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e into the Ag-Ni composite concentration, a remarkable phenomenon was observed in the absorption spectra. Specifically, the absorption band edge exhibited a noticeable red shift, and the visible light absorption capacity within the 450–500 nm range was significantly enhanced. This enhancement had a direct positive impact on the photocatalytic activity of the material. The increased absorption of light was quite evident by the optimized Ni concentration \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec\u003cb\u003e)\u003c/b\u003e and Ag concentration \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed\u003cb\u003e)\u003c/b\u003e in the graphitic carbon nitride in the UV-visible light region[\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThis enhancement in light absorption can be attributed to the interaction occurring within the valence and conduction bands of the Ag-Ni@g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e composite, thereby facilitating key Schottky barrier heterojunction charge transfer processes[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e, \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e, \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e]. When compared to other nanocomposite photocatalysts, this composite demonstrated a notably stronger capacity for absorbing visible light. This improvement in visible light absorption served to enhance the overall conversion efficiency of visible light and, consequently, further heightened the photocatalytic activity of the composite material. The optimization of the Ni and Ag concentrations in g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, as demonstrated by the spectral data, holds substantial promise for the development of highly efficient photocatalytic materials[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFurthermore, we investigated photocatalytic hydrogen generation and meticulously examined various parameters. Initially, the focal point of the investigation centred on optimizing the concentration of nickel (Ni) in the g-C\u003csub\u003e3\u003c/sub\u003eN4 heterostructures, where four distinct concentrations were considered: GCNN-1 (0.1 M), GCNN-2 (0.2 M), GCNN-3 (0.3 M), and GCNN-4 (0.4 M). Notably, within this array of concentrations, it was evident that GCNN-3 demonstrated superior performance in terms of both the hydrogen production volume and rate, achieving an impressive 638 µmol.h\u003csup\u003e− 1\u003c/sup\u003e. g\u003csup\u003e− 1\u003c/sup\u003e\u003csub\u003ecat\u003c/sub\u003e under identical experimental conditions, as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cb\u003e(a-b)\u003c/b\u003e[\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe observed phenomenon of enhanced hydrogen evolution in GCNN-3, particularly when using a concentration of 0.3 M nickel nanoparticles, can be attributed to several key factors, which are integral to comprehending this noteworthy outcome. (i) Nickel nanoparticles take on the role of co-catalysts. Co-catalysts function in concert with the photocatalyst to facilitate the production of hydrogen. Nickel, in this capacity, has a pivotal role in augmenting the overall photocatalytic activity. It does so by providing active sites conducive to hydrogen evolution and by fostering the separation of charge carriers. (ii) The Schottky effect, a fundamental principle in semiconductor physics, is pertinent here. When a junction is formed between a metal and a semiconductor, such as the amalgamation of nickel nanoparticles with g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, it results in the creation of a Schottky barrier. This barrier serves as an enabler of efficient separation of charge carriers, which is indispensable for heightening photocatalytic efficacy. Nickel, functioning as a metal co-catalyst, capitalizes on the Schottky barrier to promote and optimize charge transfer reactions, a fundamental requirement for hydrogen generation. (iii) The concentration of nickel nanoparticles has a pivotal role in fine-tuning the photocatalytic process, at a concentration of 0.3 M, a delicate equilibrium is achieved[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e]. At this threshold, nickel nanoparticles are instrumental in ensuring the effective adsorption of reactants, encompassing substances like water and other components vital to the hydrogen generation process, onto the surface of the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e heterostructure. Simultaneously, this concentration facilitates the rapid and efficient desorption of hydrogen gas once it is generated. This finely tuned balance between adsorption and desorption is critical for achieving an elevated rate of hydrogen evolution. The conspicuous elevation in both the volume and rate of hydrogen generation observed in GCNN-3, specifically when using a concentration of 0.03 M nickel nanoparticles, can be ascribed to the synergistic interplay of nickel as a co-catalyst, the promotion of Schottky charge carrier transfer reactions, and the optimization of adsorption and desorption processes. In addition, we investigated the optimization of the silver (Ag) concentration (CAN-1 (0.1 M), CAN-2 (0.2 M), CAN-3 (0.3 M), and CAN-4 (0.4 M)) on the GCNN-3 (Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) photocatalyst for improved photocatalytic hydrogen generation. The experimental observation of the CAN-2 catalyst showed a higher rate and volume of photocatalytic hydrogen generation (2507 µmol.h\u003csup\u003e− 1\u003c/sup\u003e. g\u003csup\u003e− 1\u003c/sup\u003e\u003csub\u003ecat\u003c/sub\u003e), due to the optimized silver nanoparticles having exemptional properties such as (i) serving as a photosensitizer, (ii) raising the Plasma resonance effect, and (iii) contributing to the formation of Schottky barriers[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e, \u003cspan additionalcitationids=\"CR73\" citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e–\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e]. This result extends to the exploration of optimizing the concentration of silver (Ag) in the context of the GCNN-3 photocatalyst to enhance the process of photocatalytic hydrogen generation. Remarkably, the experimental findings indicated that the CAN-2 catalyst exhibited a significantly elevated rate and volume of photocatalytic hydrogen generation, quantified at an impressive 2507 µmol.h\u003csup\u003e− 1\u003c/sup\u003e. g\u003csup\u003e− 1\u003c/sup\u003e\u003csub\u003ecat\u003c/sub\u003e (See Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e \u003cb\u003e(c- d)\u003c/b\u003e). This notable performance can be attributed to the exceptional properties exhibited by the optimized silver nanoparticles, including serving as a photosensitizer, invoking the plasma resonance effect, and contributing to the formation of Schottky barriers.\u003c/p\u003e \u003cp\u003eThe silver nanoparticles at the optimized concentration of 0.2 M act as potent photosensitizers. In the context of photocatalysis, photosensitizers are materials that enhance the absorption of light by the photocatalyst, which is crucial for driving the catalytic reaction. By sensitizing the photocatalyst, silver nanoparticles make it more responsive to light, thereby increasing the efficiency of hydrogen generation. Silver nanoparticles are renowned for their ability to exhibit the plasma resonance effect. This phenomenon is a result of the collective oscillation of conduction electrons on the surface of the nanoparticles when exposed to specific wavelengths of light. In essence, this resonance effect intensifies the interaction between light and the photocatalyst, enhancing the energy transfer efficiency, thereby promoting higher hydrogen generation rates. Silver nanoparticles contribute to the formation of Schottky barriers when interfaced with the photocatalyst. These barriers have a pivotal role in facilitating the separation of charge carriers. By enabling the efficient separation of these carriers, silver nanoparticles assist in expediting charge transfer reactions, which are a fundamental step in the photocatalytic process of hydrogen production. The experimental findings thus underscore the significance of silver nanoparticles at a concentration of 0.2 M, which not only act as photosensitizers but also invoke the plasma resonance effect and participate in the creation of Schottky barriers. This collective impact results in the remarkable enhancement of the photocatalytic hydrogen generation rate and volume, offering valuable insights for the advancement of sustainable and efficient energy production through photocatalysis.\u003c/p\u003e \u003cp\u003eIn the ongoing pursuit of refining photocatalytic hydrogen generation, our research focused on optimizing sacrificial reagent concentrations and evaluating the recyclability of the meticulously crafted photocatalyst CAN-2. A pivotal discovery emerged, wherein a sacrificial reagent concentration of 25 vol % stands out as the catalyst for significantly enhanced photocatalytic hydrogen performance, as clearly seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cb\u003e(e).\u003c/b\u003e The upswing in performance can be traced back to the optimization of the following key factors: improved charge carrier separation, heightened reactant adsorption, and efficient mingling of reactants within the solution. At the core of this advancement lies the superior separation of charge carriers, a fundamental prerequisite for efficient photocatalysis. The orchestrated interplay of electrons and holes, once excited by light, is crucial for driving the redox reactions responsible for hydrogen production. Here, the 25 vol % sacrificial reagent concentration ensures these charge carriers do not prematurely recombine but rather engage in the desired reactions, thus amplifying the rate of hydrogen generation.\u003c/p\u003e \u003cp\u003eFurthermore, the influence of this optimized concentration extends to the adsorption of reactants on the surface of the photocatalyst. By enhancing this adsorption process, the reagent concentration guarantees that a surplus of reactants is readily available for the ensuing photocatalytic reactions. This translates into a notable increase in the yield of hydrogen gas, underlining the significance of the 25 vol% threshold[\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e, \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e]. Additionally, the meticulous choice of sacrificial reagent concentration optimizes the disruption of the reactant solution, making it a highly effective medium for catalytic interactions. This dynamic interaction, brought about by the concentration selection, enables reactants to efficiently encounter the active sites of the photocatalyst, ensuring that the hydrogen generation process proceeds with remarkable efficiency. Moreover, our research also underscores the robust stability and recyclability of the custom-designed material. As aptly depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cb\u003e(f)\u003c/b\u003e, the performance of the material remained exceptional over the course of six cycles, a remarkable testament to its longevity and reliability. This extended performance lifespan holds great promise for real-world applications, where sustained and repeated usage of photocatalysts is a pivotal requirement for practical and efficient hydrogen production processes. The strategic optimization of the sacrificial reagent concentration at 25 vol % yields a substantial boost in photocatalytic hydrogen generation performance by improving the charge carrier separation, reactant adsorption, and reactant solution disruption. Furthermore, the exceptional stability and recyclability of the material across six cycles show its potential for sustainable and enduring use in the quest for clean and efficient hydrogen production[\u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e76\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e \u003cb\u003e(a-b)\u003c/b\u003e offers comprehensive insight into how the choice of light source impacts the process of photocatalytic hydrogen evolution when using a material that has been meticulously fabricated for optimal performance. Notably, our findings in this context are quite intriguing. One of the most striking observations is that when subject to identical experimental conditions, natural solar light demonstrates significantly superior hydrogen efficiency compared to simulated solar light irradiation. This outcome can be attributed to several key factors. First, natural solar light provides a substantially higher quantity of photoenergy, which fuels the photocatalytic reaction more effectively. Additionally, natural solar light encompasses a broader and richer range of the visible light spectrum when compared to its simulated solar light. This discrepancy in the spectral composition has a pivotal role in enhancing the performance of the photocatalytic process. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e \u003cb\u003e(a-b)\u003c/b\u003e shows the pivotal role the choice of light source has in the efficiency of photocatalytic hydrogen evolution, with natural solar light emerging as the more potent option due to its superior photo energy content and a more extensive visible light spectrum. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e \u003cb\u003e(c-e)\u003c/b\u003e showcases a comprehensive exploration of the photocatalytic hydrogen evolution under various monochromatic light sources, including wavelengths of 365, 400, and 450 nm, and an air mass filter of 1.5 G. Detailed and extensive calculations for the augmented apparent quantum yield efficiency can be found in the electronic supplementary information[\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eNotably, among the range of monochromatic light sources studied, the 1.5 G air mass filter emerged as the standout performer, exhibiting a remarkable increase in both the rate of hydrogen generation and apparent quantum efficiency. This exceptional performance can be attributed to its lighter intensity and its ability to harness a broader spectrum of visible light. Additionally, a comprehensive assessment involved the calculation of the UV-visible to hydrogen conversion for three distinct photocatalysts: pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, GCNN-3, and CAN-2 as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e\u003cb\u003e(f)\u003c/b\u003e. These results, available in the electronic supplementary information, revealed the following values for the UV-visible to hydrogen conversion: 0.34% for pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, an impressive 1.62% for GCNN-3, and a remarkable 6.37% for CAN-2, respectively[\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure S7 (a-d)\u003c/b\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003cb\u003e(e-f)\u003c/b\u003e discloses critical insights into the charge carrier recombination and lifetime of the initially synthesized pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, GCNN-3, and CAN-2 photocatalysts. The optimized photocatalyst exhibits a notably lower photoluminescence intensity compared to the pristine and GCNN-3 photocatalysts, indicating effective control over charge carrier recombination and photo corrosion in the reaction solution medium. The results highlight the optimized photocatalyst's ability to accomplish these crucial aspects.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe investigation extends to the lifetime of the prepared nanohybrids: g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e-12.9, GCNN-3-84.3, and CAN-2-103.8 ns (refer to \u003cb\u003eTable S2\u003c/b\u003e and \u003cb\u003eFigure S4 (e-f)\u003c/b\u003e for detailed information). Photoluminescence spectra are employed to analyse the radiative recombination efficiency of photo-generated charge carriers. \u003cb\u003eFigures S7(a-b) and\u003c/b\u003e Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003cb\u003e(f)\u003c/b\u003e depict a distinct reduction in peak intensity in defects-modified g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, underscoring the significance of nitrogen defects and surface-active sites in enhancing charge carrier separation efficiency. The peak intensity diminishes with increasing distance (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e \u0026gt; GCNN-3 \u0026gt; CAN-2), implicating defects in forming carrier traps that capture carriers and impede recombination. The emission peaks at 625, and 625 nm in the photoluminescence spectra signify band-to-band recombination of holes and electrons, correlating with surface active sites. The research reveals that the defect state and surface-active site’s structure promotes efficient carrier separation, resulting in a low recombination efficiency of photo-excited electron-hole pairs, thereby boosting photocatalytic activity. The active contribution of nitrogen defects and bi metal creates the plenty of surface-active sites for efficient water-splitting events is highlighted, facilitating the movement of charge carriers from the inside to the surface.\u003c/p\u003e \u003cp\u003eA study of the charge separation efficiency is a fundamental aspect in the realm of photoelectrochemical systems, and the provided information elucidates the evaluation of this crucial parameter in both pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and the optimized CAN-2 (Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e). Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e \u003cb\u003e(a-c)\u003c/b\u003e shows the photocurrent responses of pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and the optimized CAN-2 sample under simulated sunlight irradiation. Notably, the data reveals a remarkable enhancement in photocurrent responses over nine consecutive on-off cycles, indicating the stable reproducibility of the results. These cycles reflect the ability of the photoelectrochemical system to repeatedly generate and separate charge carriers efficiently in response to light stimulation. A distinctive behaviour is observed as the photocurrent initiates promptly when the light source is switched on and swiftly decreases to nearly zero when the light is turned off. This behaviour underlines the direct link between the incident light and the generation of the photocurrent, reinforcing the effective utilization of photons for charge separation. Significantly, both the pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and optimized CAN-2 exhibit photocurrent densities measured at 1.2 and 5.9 mA/cm\u003csup\u003e2\u003c/sup\u003e, respectively. However, the key observation is that the optimized CAN-2 sample demonstrates a notably stronger photocurrent response. This improvement is attributed to the superior separation efficiency of the photogenerated electron-hole (e\u003csup\u003e−\u003c/sup\u003e, h\u003csup\u003e+\u003c/sup\u003e) pairs in CAN-2, which is further substantiated by its enhanced activity in photocatalytic hydrogen evolution[\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eElectrochemical impedance spectroscopy (EIS) was used to delve deeper into the charge separation efficiency[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. EIS Nyquist plots provide a window into the impedance characteristics of the system, with a smaller semicircle indicating a superior charge separation efficiency. Comparing the EIS Nyquist plot of the pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with that of CAN-2, a significant transformation becomes evident (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003cb\u003e(d)\u003c/b\u003e). The semicircle representing impedance in the Nyquist plot of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e reduces noticeably after the introduction of the Ag-Ni modification. This decrease in impedance indicates a substantial reduction in the recombination of charge carriers, signifying a considerable improvement in the charge separation efficiency. The order of this impedance reduction follows the sequence CAN-2 \u0026lt; g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, with CAN-2 exhibiting the most significant enhancement. The reduction in charge carrier recombination serves as a pivotal factor contributing to the superior photoelectrochemical performance of the CAN-2 sample. The enhanced charge separation efficiency in the optimized CAN-2 sample, evident by both the photocurrent response and EIS Nyquist plots, underscores its superior photoelectrochemical performance. This improvement is linked to the reduction in charge carrier recombination, resulting in a more effective separation of photogenerated electron-hole pairs. The findings presented here offer profound insights into the design and optimization of photoelectrochemical systems, with relevance to applications involving photocatalytic hydrogen processes.\u003c/p\u003e \u003cp\u003eX-ray Photoelectron Spectroscopy (XPS) measurements were done to gain insights into the composition and electronic structure of the CAN-2 photocatalysts full scan survey spectrum as shown in \u003cb\u003eFigure S8\u003c/b\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e \u003cb\u003e(a)\u003c/b\u003e reveals the high-resolution XPS spectra of the C 1s peak, deconvoluted into two main peaks at 284.3 and 285.2 eV. These peaks are attributed to the graphitic carbon (C = C) and sp\u003csup\u003e2\u003c/sup\u003e-hybridized carbon found in the N-containing aromatic rings (N-C = N), respectively. Additionally, a new peak at 287.2 eV is observed in the CAN-2 samples, indicating the presence of C-Sp\u003csup\u003e2\u003c/sup\u003e bonds arising from the Ag-Ni particles[\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e, \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e81\u003c/span\u003e]. In Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e, the N 1s spectrum shows three distinctive peaks at 398.1 eV (Pyridinic-N), 399.1 eV (Pyrrolic-N), and 400.1 eV (Graphitic-N). However, it is worth noting that the nitrogen-bridging species exhibit a shift in the peak position for CAN-2, suggesting an electron structural change in this sample. In Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e(c)\u003c/b\u003e, the Ni 2p spectrum of the Nickel particles is shown, revealing four critical peaks. Peaks at 872.9 and 855.4 eV correspond to Ni 2p\u003csup\u003e1/2\u003c/sup\u003e and 2p\u003csup\u003e3/2\u003c/sup\u003e, respectively, while satellite peaks at 878.5 and 860.9 eV indicate that Ni primarily exists in the metallic state, with only a minor quantity in the + 2-oxidation state [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e79\u003c/span\u003e]. In Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e(d)\u003c/b\u003e, the Ag 3d spectrum highlights two major peaks at 367.7 and 376.2 eV, corresponding to Ag-3d\u003csub\u003e5/2\u003c/sub\u003e and 3d\u003csub\u003e3/2\u003c/sub\u003e. These peaks suggest that Ag atoms are deposited on the triazine rings of the carbon nitride during thermal polymerization. The presence of Ni-Ag atoms likely enhances the electronic density and promotes π-π stacking interactions between the Ag-Ni nanoparticles and conjugated tri-s-triazine units in the polymeric graphitic carbon nitrides[\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo assess the specific surface areas of the three samples, nitrogen adsorption-desorption isotherms and pore size distribution were measured (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e(e-f)\u003c/b\u003e). Pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and CAN-2 photocatalysts exhibit isotherms with an H3-type hysteresis loop, indicative of mesopores. This result aligns with the observed morphology in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed-f. In contrast, CAN-2 exhibits lower N\u003csub\u003e2\u003c/sub\u003e adsorbed volumes, potentially due to a lack of porosity. Pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e holey grain heterostructures also show poor N\u003csub\u003e2\u003c/sub\u003e adsorption. The specific surface area and pore volume of CAN-2 are 347.2 m\u003csup\u003e2\u003c/sup\u003e/g and 6.8 cm\u003csup\u003e3\u003c/sup\u003e/g, respectively, surpassing those of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, which has a specific surface area of 157.2 m\u003csup\u003e2\u003c/sup\u003e/g and a pore volume of 3.2 cm\u003csup\u003e3\u003c/sup\u003e/g. Comparing CAN-2 with pristine g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, it is evident that the optimized photocatalyst boasts a larger surface area and pore volume. This configuration provides more reactive sites and numerous boundaries, which significantly contribute to the photocatalytic process, enhancing the redox reactions and ultimately improving hydrogen efficiency[\u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo understand the improved hydrogen evolution by Ag blending with Ni nanoparticles, the H\u003csub\u003e2\u003c/sub\u003eO dissociation was calculated using DFT calculations on the Ni/GCN and Ag-Ni/GCN models. Details on the modelling of metal deposited GCN can be found in the electronic supplementary information (\u003cb\u003eFigures S9\u0026amp;S10\u003c/b\u003e). On Ni/GCN, H\u003csub\u003e2\u003c/sub\u003eO adsorbs on the top site of Ni with an adsorption energy of ‒0.76 eV shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e. The OH and H, dissociated from H\u003csub\u003e2\u003c/sub\u003eO, adsorb on the bridge site and 3-fold site, respectively. The H\u003csub\u003e2\u003c/sub\u003eO dissociation process exhibits an activation energy of 1.29 eV and a reaction energy of ‒0.38 eV (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e\u003cb\u003e(c)\u003c/b\u003e). On Ag/GCN, it was found that H\u003csub\u003e2\u003c/sub\u003eO preferentially adsorbs on the top site of Ni with an adsorption energy of ‒0.93 eV rather than on the Ag site (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e). The adsorbed H\u003csub\u003e2\u003c/sub\u003eO dissociates into OH and H along the Ni atoms. The activation energy and reaction energy were found to be 0.65 and ‒0.08 eV, respectively. The results show that blending Ag atoms into the Ni particle significantly decreases the activation energy from 1.29 to 0.65 eV, producing more atomic hydrogen on the surface.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe Gibbs free energy for the adsorption of atomic hydrogen (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varDelta {G}_{{H}^{\\ast }}\\)\u003c/span\u003e\u003c/span\u003e) is a common activity descriptor for the hydrogen evolution reaction[\u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e]. An ideal catalyst for the HER exhibits \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varDelta {G}_{{H}^{\\ast }}\\)\u003c/span\u003e\u003c/span\u003e closes to zero. Therefore, the Gibbs free energy for H adsorption was calculated for different sites on Ni/GCN and Ag-Ni /GCN (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e). On Ni/GCN, atomic hydrogen preferentially adsorbs on the Ni-Ni-Ni 3-fold sites. The geometry of the most favourable adsorption in Ni/GCN is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e, with a corresponding Gibbs free energy of ‒0.39 eV. The large negative value (‒0.39 eV) indicates that atomic hydrogen binds too strongly to the Ni-Ni-Ni site, preventing the production of molecular hydrogen. On the other hand, bridge sites (Ni-Ni, Ni-Ag, and Ag-Ag) exhibit preferential adsorption of atomic hydrogen on Ni-Ag/GCN, and blending Ag reduces the H adsorption strength. The Ni-Ni site in Ag-Ni /GCN (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u003cb\u003e(c)\u003c/b\u003e), with a Gibbs free energy of ‒0.20 eV, shows a higher HER activity compared to the Ni-Ni-Ni site in Ag-Ni /GCN. The Gibbs free energy for the Ni-Ag site was 0.01 eV, indicating that it is the optimal site for hydrogen evolution (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u003cb\u003e(d)\u003c/b\u003e). However, atomic hydrogen binds too weakly on the Ag-Ag site to generate molecular hydrogen (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u003cb\u003e(e)\u003c/b\u003e), with a Gibbs free energy of 0.33 eV. Overall, these results explain the higher HER activity on Ag-Ni /GCN compared to Ni/GCN.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe density of states (DOS) for metal atoms was calculated to analyse the impact of blending Ag on the weakened H adsorption energy. It is known that when the DOS is located further from the Fermi level in the negative direction, the H adsorption strength decreases[\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e\u003cb\u003e(a-b)\u003c/b\u003e shows that the DOS of the Ni atoms shifts downward when mixed with Ag atoms. Furthermore, the DOS of the Ag atoms in Ag-Ni/GCN (CAN-2) is placed at a greater distance from the Fermi level compared to the DOS of the Ni atoms. These findings conclude that Ag atoms diminish the strength of the H adsorption by downwardly shifting the DOS, thereby mitigating the strong interaction between H and Ni. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e\u003cb\u003e(c)\u003c/b\u003e provides insight into the behaviour of the optimized photocatalyst, which was meticulously engineered, with particular attention to its work function and various characterization properties. This photocatalyst, denoted as CAN-2 and consisting of Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e(CAN-2), uses a Schottky barrier charge transfer reaction mechanism (See in \u003cb\u003eFigure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e). This mechanism is of paramount importance in enhancing the efficiency of the hydrogen generation. The synergy between the components of the photocatalyst and the Schottky barrier substantially improves the transfer of charge during the hydrogen generation process, resulting in an overall enhanced performance[\u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e85\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe photocatalytic process begins with the illumination of the photocatalyst, which results in the absorption of photon energy. Subsequently, charge carriers, including electrons (e\u003csup\u003e−\u003c/sup\u003e) and holes (h\u003csup\u003e+\u003c/sup\u003e), are generated within the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e hetero-nanostructures. These charge carriers have a pivotal role in the ensuing sequence of reactions. The holes (h+) migrate to the valence band, instigating a crucial step: water oxidation. During this phase, water molecules are cleaved, leading to the release of H\u003csup\u003e+\u003c/sup\u003e ions, accompanied by the formation of oxidized intermediates. Silver metal has a significant role as a photosensitizer in this process. It acts as a catalyst for the generation of electrons, which are then introduced into the conduction band of the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e through a Schottky barrier. This step is vital for the efficient separation of charge carriers and the promotion of electron mobility. Notably, nickel emerges as a co-catalyst, serving to rapidly capture electrons from the conduction band of the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. This function is critical in preventing the undesirable recombination of electrons and holes, ensuring an efficient charge separation process.\u003c/p\u003e \u003cp\u003eThe captured electrons proceed to react with the generated H\u003csup\u003e+\u003c/sup\u003e ions. These reactions culminate in the formation of hydrogen gas (H\u003csub\u003e2\u003c/sub\u003e), a clean and sustainable source of fuel. This intricate photocatalytic system harnesses the power of light to drive the conversion of water into hydrogen fuel, presenting a promising avenue for renewable energy production without relying on conventional, non-renewable resources[\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e, \u003cspan citationid=\"CR86\" class=\"CitationRef\"\u003e86\u003c/span\u003e].\u003c/p\u003e "},{"header":"Conclusions","content":"\u003cp\u003eIn this ground-breaking investigation, we have achieved a significant breakthrough in the field of photocatalysis by designing and synthesizing a novel hetero-structured Ag-Ni/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e material with a unique surface modification configuration. To enhance its photocatalytic performance, we meticulously optimized the concentration of Ag-Ni alloy nanoparticles for surface modification and active site enhancement. Through rigorous physicochemical analyses and the utilization of DFT calculations, we unveiled the pivotal role of graphitic carbon nitride (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) in facilitating efficient charge transfer and effective separation of photo-generated carriers and visualization hydrogen bubbles by in-situ TEM studies. Notably, the strategic incorporation of Ag-Ni nanoparticles into the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e lattice at specific positions led to the formation of the valence band maximum (VBM). Additionally, the hetero microstructure composed of thin g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nanotubes coupled with nanosheets has a crucial role in reducing carrier migration distances, thereby effectively suppressing carrier recombination. As a result, this hetero-structured g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e material not only has an exceptionally high surface area but also provides an abundance of active sites for catalytic reactions. These exceptional characteristics collectively culminated in an outstanding solar light-driven photocatalytic H\u003csub\u003e2\u003c/sub\u003e evolution rate of 2507 µmol h\u003csup\u003e− 1\u003c/sup\u003e g\u003csup\u003e− 1\u003c/sup\u003e, surpassing the rate achieved by bulk g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e by an impressive 18.6-fold. Furthermore, the apparent quantum efficiency of this hetero-structured material reached an exceptional value of 1.6% under a 1.5 G air mass filter. Our pioneering work has successfully accompanied in a new era of photocatalysis through the development of this remarkable hetero-structured g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e material. Its exceptional properties and performance hold great promise for a wide range of applications in harnessing solar energy for catalytic reactions and other advanced technologies.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (MSIT), Dr. V. Navakoteswara Rao gratefully acknowledges the Brain Pool program of MSIT [Project Number 2021H1D3A2A02081839]. This work was also supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (MSIT)\u0026nbsp;(RS-2023-00248428) and\u0026nbsp;ERC Centre funded by the National Research Foundation of Korea (NRF-2022R1A5A1033719).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e☒\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e☐ The authors declare the following financial interests/personal relationships which may be considered as potential competing interests\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eV Navakoteswara Rao, Conceptualization, Investigation, Catalyst fabrication, Software, Formal analysis, Writing-Original Draft, Funding Acquisition.Hyunguk Kwon Investigation Theoretical studies (DFT), Software M Nagaveni, Visualization, Data Curation for photocatalysis P Ravi, Visualization, Data Curation for Photoelectrochemical analysis Yonghee Lee, Investigation, Formal analysis for materials Synthesis Seong Jae Lee, Investigation, Formal analysis for DFT Kyeounghak Kim, Resources, Supervision for DFT analysis M V Shankar, Validation, Manuscript reviewing for photocatalysis hydrogen generationJung Ho Yoo Resources, Supervision for in-situ TEM Chiwon Ahn, Resources, SupervisionSan-jae Kim Writing \u0026ndash; Review \u0026amp; Editing, SupervisionJun Mo Yang Conceptualization, Writing, Review \u0026amp; Editing, Supervision, Project Administration, Funding Acquisition.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eTahir M, Tahir B (2020) 2D/2D/2D O-C3N4/Bt/Ti3C2Tx heterojunction with novel MXene/clay multi-electron mediator for stimulating photo-induced CO2 reforming to CO and CH4. 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ACS Appl Energy Mater 4:11982\u0026ndash;12006\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Scheme","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Hetero-structured, Surface-active site, Solar, Photocatalyst, and quantum efficiency","lastPublishedDoi":"10.21203/rs.3.rs-3971500/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3971500/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe advancement of photocatalysis relies on the development of novel hetero-structured materials with unique architectures. In this study, we successfully synthesized a hetero-structured g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (GCN) material with a distinctive surface modification. To further enhance its photocatalytic performance, we optimized the Ag-Ni concentration to maximize the active sites for hydrogen evolution reactions. By using systematic physicochemical characterizations and density functional theory (DFT) calculations, we elucidated the pivotal role of graphitic carbon nitride (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) in facilitating the formation of an efficient charge transfer channel and promoting the effective generation and separation of photo-generated carriers. From the DFT calculations, we also demonstrated that the Ag-Ni nanoparticles provide more efficient active sites than Ni nanoparticles for water splitting and hydrogen evolution and In-situ TEM exploration. Furthermore, the hetero microstructure consisting of thin g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nano scrolls has a crucial role in shortening the migration distance of the carriers, effectively suppressing carrier recombination. Consequently, these extraordinary characteristics resulted in a superior solar light-driven photocatalytic H\u003csub\u003e2\u003c/sub\u003e evolution rate of 2507 \u0026micro;mol h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, surpassing the rate achieved by bulk g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e by a remarkable 18.6-folds. Moreover, the apparent quantum efficiency of this hetero-structured material reached an exceptional value of 1.6% under a 1.5 G air mass filter.\u003c/p\u003e","manuscriptTitle":"Tailoring Schottky Barriers and Active Sites in Bi-metallic Cluster Mesoporous Carbon Nitride Heterostructures nanocomposite for Hydrogen Evolution with In-situ insights","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-11 13:10:18","doi":"10.21203/rs.3.rs-3971500/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"71ee7094-830f-499f-b3e0-a13ed69724e2","owner":[],"postedDate":"March 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-04-13T01:14:24+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-11 13:10:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3971500","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3971500","identity":"rs-3971500","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}