Facile Construction of a Ternary Ag/TiO₂/g-C₃N₄ Nanocomposite with Boosted Visible- Light Photocatalytic Activity

Facile Construction of a Ternary Ag/TiO₂/g-C₃N₄ Nanocomposite with Boosted Visible- Light Photocatalytic Activity | 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 Facile Construction of a Ternary Ag/TiO₂/g-C₃N₄ Nanocomposite with Boosted Visible- Light Photocatalytic Activity Hamza El-Hosainy, Alaa A. Alhashash, Abd El-Motaleb Ramadan, Ezz-Elregal M. Ezz-Elregal, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6826016/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 13 You are reading this latest preprint version Abstract In this study, a novel biphasic anatase/brookite TiO₂ was successfully deposited onto g-C₃N₄ via an impregnation method, followed by the photodeposition of Ag nanoparticles to construct a ternary Ag/TiO₂/g-C₃N₄ nanocomposite. Detailed physicochemical characterizations confirmed the successful immobilization of Ag nanoparticles on the TiO₂/g-C₃N₄ surface, contributing to a significantly enhanced surface area, broadened visible light absorption, and improved charge carrier separation. The photocatalytic performance of the resulting nanocomposites was evaluated through the reduction of p-nitrophenol (PNP) to p-aminophenol (PAP), revealing a remarkable enhancement in activity with increasing Ag content. Notably, the 2% Ag/TiO₂/g-C₃N₄ nanocomposite exhibited a photocatalytic rate approximately 3 times higher than that of 0.5% Ag/TiO₂/g-C₃N₄, twice that of 2% Ag/TiO₂ (commercial)/g-C₃N₄, and significantly superior to bare TiO₂/g-C₃N₄. The outstanding photocatalytic efficiency of the 2% Ag/TiO₂/g-C₃N₄ system is attributed to its superior light-harvesting ability and efficient charge separation via a Z-scheme mechanism. These findings present a promising and scalable strategy for engineering advanced ternary nanocomposite photocatalysts with enhanced environmental remediation capabilities. TiO2 g-C3N4 AgNPs Photocatalyst Nitrophenol Reduction Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1.Introduction The rapid growth of population and industry generates significant amounts of effluents with toxic heavy metals and organic pollutants, introducing them into the ecosystem and making water pollution one of the major environmental issues facing the world today [ 1 ]. Nitroarenes, particularly p-nitrophenol (PNP), are among the most hazardous contaminants present in wastewaters [ 2 ]. PNP is used in several applications, including pesticides, petroleum refining, dyeing and various chemical industries [ 3 , 4 ]. The presence of this compound in water can pose serious health risks to humans such as eye burns, respiratory problems, and skin allergies. If ingested, it may also irritate the digestive tract and cause nausea, vomiting, and diarrhea.[ 5 ]. As a result, developing efficient methods to eliminate these organic pollutants from water is crucial. Recently, there are a number of techniques that can be used, including physical methods such as filtration, adsorption and sedimentation[ 6 ], chemical methods like coagulation, photocatalytic degradation, ozonation, chemical precipitation and ion exchange[ 7 ] and biological methods, including aerobic and anaerobic treatment[ 8 ]. Among these methods, the best alternative for traditional wastewater treatment methods is semiconductor heterogeneous photocatalysis. This is due to its capacity to transform solar energy considered the ultimate renewable energy source for powering activities on Earth into chemical energy[ 9 ], produce fewer toxic and harmful secondary pollutants, and remove a variety of contaminants from different media [ 10 ]. Numerous semiconductor nanomaterials, including BiVO 4 , Ag 3 PO 4 , g-C 3 N 4 , ZnO, TiO 2 , SnO 2 , AlO 3 and Fe 2 O 3 , have been extensively researched for their ability to remove water pollutants[ 11 – 17 ]. However, TiO 2 has received the most research attention among these semiconductors and is found in three natural phases: brookite, anatase, and rutile [ 18 – 20 ]. TiO 2 has many advantages such as non-toxicity, affordability, strong oxidizing power, remarkable photochemical stability, and environmentally favorable qualities [ 21 ]. The photocatalytic characteristics of TiO 2 are mainly attributed to its anatase phase due to its favorable band alignment, which provides a strong driving force for electron transfer to molecular oxygen. However, both anatase and brookite phases are considered more crucial for reducing carrier recombination rates, as the band alignment between these two TiO 2 isomorphs enhances overall performance[ 22 ]. Despite all these advantages, TiO 2 faces certain limitations, such as a broad gap between bands (3.2 eV) that restricts its absorbing ability to the UV range only, thereby reducing its photocatalytic efficiency and causing rapid electron-hole recombination. Overcoming these restrictions is through the metal deposition [ 23 ], non-metal doping [ 24 – 26 ], or coupling with semiconductors, that have smaller bandgap energies, which allows absorption in the spectrum's visible region, and lowers the charge carriers recombination rate [ 27 ]. On the other hand, graphitic carbon nitride (g-C 3 N 4 ), a semiconductor that has recently gained popularity for a variety of uses, as it has substantial surface area, chemically stable nature, affordability, and strong adsorptive capabilities. It can be prepared through simple methods such as the thermal polymerization of rich nitrogen precursors like urea, melamine or dicyandiamide. Additionally, g-C₃N₄ demonstrates promising performance in photocatalysis owing to its remarkable capacity to absorb visible light at 460 nm and its modest energy band gap (2.7 eV) [ 28 , 29 ].A TiO 2 /C 3 N 4 heterojunction formed by combining semiconductors with a broad (TiO 2 ) and a narrow (g-C 3 N 4 ) band gap, can expand the absorption border to the visible light range while also improving charge carrier separation performance. [ 30 ]. However, this heterojunction still has some drawbacks, such as fast charge recombination and reduced photocatalytic efficiency [ 31 ]. To address this issue, doping or depositing TiO 2 /g-C 3 N 4 by noble metals has been proposed. The composite's photocatalytic efficiency of TiO 2 and C 3 N 4 has frequently been enhanced after the photo-deposition of noble metals. For instance, Ag NPs can be used as a surface catalytic center for the photoreduction reaction and help prevent the charge recombination. These Ag NPs can capture the photogenerated electrons during photocatalysis process and release them to break down the contaminants [ 32 , 33 ]. In this work, biphasic anatase/brookite TiO 2 was deposited onto g-C 3 N 4 using an impregnation method. Following this, Ag nanoparticles were deposited onto TiO₂/g-C₃N₄ via photodeposition, promoting a Z-scheme charge transfer mechanism. The synthesized composite demonstrated strong photocatalytic activity when para-nitrophenol (PNP) is converted to para-aminophenol (PAP). The Z-scheme mechanism in the photocatalyst reduces charge carrier recombination and enhances redox potential, thereby boosting its photocatalytic performance. 2. Materials and methods Titanium tetraisopropoxide (Ti[OC 3 H 7 ] 4 ), and Pluronic (P123) were sourced from Sigma-Aldrich, Urea (CH 4 N 2 O) was acquired from Advent Company, Ethanol (C 2 H 5 OH), and Methanol (CH 3 OH)were obtained from chem-lab Company, and Silver nitrate (AgNO 3 ) was supplied by Merck. All chemicals were utilized just as it was delivered, without any additional processing. 2.1. Synthesis of biphasic anatase/brookite TiO 2 In a standard synthesis process, utilizing 100 mL of distilled water, 3.5 g of Pluronic was submerged within a breaker of 250 mL and stirred at 80°C for 1 hour. While stirring, 20 mL of titanium isopropoxide was gradually introduced to form a colloidal sol, 0.2 M NaOH was then used to bring the pH to 8. To facilitate the hydrolysis reaction, the resulting blend was then put in an autoclave with Teflon liner and heat it over 15 hours to 110°C. Once the temperature has dropped to ambient temperature, the obtained gel underwent a 12-minute centrifugation at 10,000 rpm then rinsed 3 times with distilled water. Finally, 12 hours were spent drying the purified precipitate at 60°C, yielding the finished powder of TiO₂. 2.2. Preparation of g-C 3 N 4 A typical thermal polycondensation technique was used to synthesize the g-C 3 N 4 .[ 34 ]. The procedure was as follows: A muffle furnace was employed to heat a crucible containing 10 g of urea for 4 hours at 550°C with a ramp rate of 2°C per minute. Once it had cooled down to ambient temperature, a fine powder was made from the resulting yellow chunk for subsequent use. 2.3. Formation of the TiO 2 /g-C 3 N 4 nanocomposite To form the g-C 3 N 4 /TiO 2 nanocomposite, a 1:1 weighing ratio of titania and graphitic carbon nitride was combined with 30 mL of ethanol in a 50 mL beaker. Following 12 hours of continuous stirring, the mixture underwent ultrasonic treatment for 30 minutes. Centrifugation was then utilized to separate the resulting precipitate for ten minutes at 10,000 rpm and subsequently air-dried at 60°C for a duration of 12 hours. 2.4. Synthesis of Ag NPs onTiO 2 /g-C 3 N 4 heterojunction The Ag(x %) /g-C 3 N 4 /TiO 2 nanocomposite, with x = 0.5, 1, 2 wt%, was produced through the process of photodeposition. Specifically, a calculated amount of AgNO 3 was mixed with 0.1 g of the g-C 3 N 4 /TiO 2 nanocomposite within a 50 mL beaker filled with 3 mL of methanol and 7 mL of distilled water. The mixture underwent stirring for three hours under light conditions (240 V, 500 W, and 6000 Lumen). Subsequently, Centrifugation of the solution was performed for 12 minutes at 10,000 rpm. The produced precipitate was washed 3times and let to air dry at 60°C for 12 hours. 2.5. Characterization The materials' phase composition and crystallinity were analyzed by X-ray Diffractometry (XRD) with a Bruker D8 diffractometer, which features Cu-Kα radiation (λ = 0.15406 nm) and a secondary monochromator. For looking into the surface's chemical constitution, X-ray Photoelectron Spectroscopy (XPS) was practiced out using a Thermo VG Multilab 2000 (England) in the 0–4 keV energy range. The nanostructure’s size and morphology were assessed through transmission electron microscopy (TEM) using a JEOL-JEM-2100 (Tokyo, Japan) operating at 200 kV. Additionally, scanning electron microscopy (SEM) was employed for morphological analysis, utilizing an energy-dispersive X-ray (EDX) detector (S-3400 N II, Hitachi, Japan) integrated into a Sirion FEI microscope. For Optical properties, diffuse reflectance and absorbance spectra (UV-Vis DRS) using a JASCO V-770 spectrophotometer were employed to quantify it. To quantify photoluminescence (PL), data were gathered utilizing a JASCO FP8600 spectrofluorometer. Fourier transform infrared (FT-IR) spectroscopy was conducted via a JASCO FTIR-6800 within the 400–4000 cm⁻¹ range. The zeta potential was determined via dynamic light scattering (DLS) with a tool from Brookhaven Instruments (USA). Finally, the specific region of surface and size of pores dispersion were assessed by a Quantachrome analyzer (Nova Series, UK) via N₂ adsorption-desorption isotherms 2.6. The Photo (catalytic) transformation of nitrophenol (NP) to aminophenol (AP) The composite's photo-catalytic efficiency was tested through converting NP to AP during sun radiation and darkness. The reaction in dark, 2.8 mL of distilled water was combined with 40 µL of NP (0.01M) in a cuvette. Next, 80 µL of newly made NaBH 4 solution (0.5 M) has been provided. Upon adding NaBH 4 , we observed that the solution's color changed to bright yellow. After that, the previous mixture was supplemented with 10µL of (5 mg/mL) catalyst. During the reaction, we noticed yellow to colorless change in the solution's color. The reaction progress was tracked using (UV-Vis) spectroscopy. The photocatalytic process followed the same procedure but was carried out under direct sunlight. 3. Results and discussion 3.1. Ternary Ag/g-C 3 N 4 /TiO 2 nanocomposite characterization In this research, a biphasic anatase/brookite TiO 2 was combined with g-C 3 N 4 through a direct impregnation method. Following this, a photodeposition technique was employed to deposit nanoparticles of silver onto the TiO 2 /g-C 3 N 4 nanocomposite, as displayed in Fig.1 . The materials' Phase arrangement and crystallinity were assessed by X-ray diffraction (XRD). The XRD patterns of TiO 2 , g-C 3 N 4 , TiO 2 /g-C 3 N 4 , and 2% Ag/TiO 2 /g-C 3 N 4 photocatalysts are displayed in Fig. 2(a) . Based on the findings, the bare TiO 2 nanoparticles exhibited a combination of both anatase and brookite phases. The anatase phase of TiO₂ demonstrates XRD peaks at 2θ = 25.2°, 37.8°, 47.9°, 54.0°, and 62.6° for planes (101), (004), (200), (105), and (204) (JCPDS 21-1271). On the other hand, the primary diffraction peak for the brookite phase of TiO 2 was identified at a 2θ value of 30.8°, associated with the (121) crystal plane. Regarding to g-C 3 N 4 , a prominent and broad peak at 27.4 o was identified, characteristic of the (002) pattern, while the g-C 3 N 4 's in-plane repeating units were accountable for the (100) faint diffraction peak at 13 o . [35]. Whereas The appearance of diffraction peaks for TiO 2 and g-C 3 N 4 in the TiO 2 /g-C 3 N 4 composite sample indicates that the two materials were effectively combined, with a weak peak of g-C 3 N 4 at 27.4°.The 2% Ag/TiO 2 /g-C 3 N 4 XRD patterns did not exhibit any additional peaks, likely due to the minor concentration and high spread of Ag nanoparticles on the TiO 2 /g-C 3 N 4 composite's surface. On the other hand, the chemical composition and specific functional groupings found within samples are ascertained via FT-IR spectroscopy. As illustrated in Fig. 2(b) , the main peaks for pure TiO 2 observed at 400–700cm −1 are designated for the modes of Ti-O-Ti and Ti-O bending vibration [36] . The peaks at around 1650 and 3000–3500 cm −1 are related to bending and stretching vibrations of hydroxyl groups[37]. In g-C 3 N 4 's FT-IR spectrum, the distinctive breathing modes of tri-s-triazine units are responsible for the 812 cm -1 peak. The CN heterocycles' stretching vibrations are responsible for the strong absorption band within1200 and1700 cm -1 . The vibrational stretching modes of terminal N-H and O-H were identified as the cause of the large peak at 3000-3650 cm -1 .[28].All the absorption peaks mentioned above were shown in TiO 2 / g-C 3 N 4 and without changes, demonstrating that during the formation of the composite, neither the structure of TiO 2 nor that of g-C 3 N 4 was destroyed. Additionally, all the primary distinctive TiO 2 and g-C 3 N 4 peaks were apparent in the Ag/TiO 2 /g-C 3 N 4 ternary composite, confirming their coexistence. Diffuse reflectance spectroscopy (DRS) is essential for evaluating the optical properties and absorption profiles of samples. As illustrated in Fig. 2(c) , TiO 2 shows an absorption edge in the (UV) range at around 390 nm, which is equivalent to an indirect band-gap energy (Eg) of 3.2 eV, as indicated in Fig. 2(d) [38-40]. In contrast, g-C 3 N 4 exhibits an absorbing edge in the visible range at 440 nm and a band-gap energy of 2.79 eV. When g-C 3 N 4 is combined with TiO 2 , the absorption edge moves into the visible spectrum at 460 nm, and the band gap energy becomes 2.74 eV. After depositing varying amounts of Ag nanoparticles onto the TiO 2 /g-C 3 N 4 surface, a noticeable red shift in the absorption edge towards the g-C 3 N 4 range was observed. The 2% Ag/TiO 2 /g-C 3 N 4 sample demonstrated an optimal band-gap energy of 2.75 eV as displayed in Fig. 2(d) . To investigate the texture, porosity, and surface area of the prepared samples, Pore size distribution curves were plotted alongside N 2 adsorption-desorption isotherms. The typical mesoporous structure of TiO₂ with a moderate surface area is shown in Fig. 3(a) , as indicated by the adsorption-desorption isotherm and the hysteresis loop's presence, which suggests cylindrical pores. On the other hand, g-C 3 N 4 exhibits a lower surface area due to its layered structure, with fewer pores compared to TiO₂. Thus, Pure TiO 2 has a greater BET surface area (190.7 m 2 /g) than g-C 3 N 4 (114 m 2 /g). However, incorporating Ag into the TiO₂/g-C 3 N 4 composite slightly increases the surface area (118 m²/g) compared to g-C 3 N 4 , enhancing the adsorption capacity as a result of the components' synergistic effect. The hysteresis loop in the Ag/TiO 2 /g-C 3 N 4 composite suggests the presence of mesopores, while the sharp rise in adsorption at higher P/P₀ values indicates capillary condensation within the pores. Furthermore, distributions of pore size in TiO₂, g-C 3 N 4 and Ag/TiO 2 /g-C 3 N 4 nanocomposites exhibit distinct characteristics as shown in Fig. 3(b) . TiO₂ displays a Pore size on average of approximately 6.1 nm, while both g-C 3 N 4 and Ag/TiO 2 /g-C 3 N 4 photocatalysts have average pore sizes around 5.2 nm. Notably, the pore size distribution peak for TiO₂ is broader compared to the sharper peaks observed for g-C 3 N 4 and Ag/TiO 2 /g-C 3 N 4 . This broader peak indicates a wider range of pore sizes in TiO₂, suggesting a more heterogeneous pore structure. In contrast, the narrower peaks for g-C 3 N 4 and Ag/TiO 2 /g-C 3 N 4 samples imply more uniform pore size distributions. These differences in pore size uniformity can significantly influence the materials' surface areas and, consequently, their photocatalytic performances. A more uniform pore size distribution, as seen in Ag/TiO₂/g-C₃N₄, typically facilitates better adsorption and diffusion of reactant molecules, potentially enhancing photocatalytic efficiency. The zeta potential analysis, shown in Fig.3(c) , highlights the surface charge differences among TiO₂, g-C 3 N 4 , and the Ag/TiO₂/ g-C 3 N 4 photocatalysts. TiO₂ exhibits a zeta potential approximately -24.70 mV, suggesting good stability in dispersion due to electrostatic repulsion. g-C 3 N 4 shows a less negative zeta potential of around -18.33 mV, indicating moderate surface charge and stability in colloidal form. Adding silver to the TiO₂/ g-C 3 N 4 composite causes a shift in the zeta potential toward a more negative value, around -41.70 mV. This shift indicates a change in surface properties and charge distribution upon nanoparticle incorporation, confirming the increase in the nanocomposite's dispersion stability and catalytic efficiency in aqueous environments. Conversely, the oxidation states and chemical contents of the produced samples were ascertained using XPS analysis. The elements Ti, O, N, C, and Ag are found in the Ag/TiO 2 /g-C 3 N 4 XPS survey spectra (see Fig.4 (a)) . The Ag (3d) peaks in Fig. 4(b) at 368.15 and 374.11 eV they belong to Ag3d 5/2 and Ag3d 3/2 of metallic Ag, respectively[41] . O 2- and O-H bonds are illustrated by the peaks in the O1s spectra, Fig. 4(c) , at 529.8 and 531 eV, respectively [42].According to Fig. 4(d) , the identified peaks at 458.5 and 464 eV correspond to Ti2p 3/2 and Ti2p 1/2 , respectively. In Fig. 4(e) , the XPS spectra of C (1s) revealed two distinct peaks at 284.75 eV and 288 eV, In accordance with sp²-hybridized carbon (C−C) and sp²-bonded carbon (N−C=N), respectively. Similarly, Fig. 4f displays three primary N (1s) peaks at 398.56 eV, 400.16 eV, and 401.4 eV associated with sp²-hybridized nitrogen (C=N−C), sp³-hybridized tertiary nitrogen (N-(C)₃), and terminal amino functional groups containing a single hydrogen atom (C−N−H) within heptazine rings, respectively [43]. Based on these findings, thus, it may be stated that the Ag/TiO₂/g-C₃N₄ nanocomposite was successfully synthesized with excellent structural properties. The TEM images illustrate the morphological features of the formed nanocomposites as indicated in Fig. 5 . The combination of TiO₂/g-C₃N₄ is depicted in Fig. 5(a) , revealing a homogeneous spread of TiO₂ nanoparticles on the g-C₃N₄ matrix, which is indicative of successful heterojunction formation. The HR-TEM image (Fig. 5(b)) of the TiO₂/g-C₃N₄ nanocomposite revealed distinct lattice fringes corresponding to both anatase and brookite phases of TiO₂, as well as g-C₃N₄. Specifically, lattice spacings of 0.35 nm and 0.29 nm were attributed to the (101) plane of anatase and the (121) plane of brookite, respectively, confirming the coexistence of biphasic TiO₂. Additionally, the presence of g-C₃N₄ was identified by the lattice spacing of 0.32 nm, corresponding to the (002) plane. These observations collectively indicate the successful formation of a heterojunction structure. Fig. 5(c) show the HRTEM of 2% Ag/TiO₂/g-C₃N₄ nanocomposite, where Ag nanoparticles are observed to be spread equally across the TiO₂/g-C₃N₄ surface, suggesting effective Ag's inclusion in the composite structure. Image Fig.5(d) provides (HRTEM) image of the 2% Ag/TiO₂/g-C₃N₄ sample, displaying the presence of Ag NPs as confirmed by the lattice spacing of the 0.23 nm (111). These observations suggest the successful formation of the Ag/TiO 2 /g-C 3 N 4 nanocomposite with potential for higher photocatalytic performance due to improved charge separation and light absorption facilitated by Ag. 3.2. ( Photo ) catalytic behavior of the prepared photocatalysts 3.2.1. Conversion of para-nitrophenol (PNP) to para-aminophenol (PAP) To assess the prepared samples' (photo) catalytic behavior, PNP was reduced to PAP by employing NaBH 4 as the reaction's reducing agent. For catalytic reaction, as shown in Fig. 6(a) , at zero time, when NaBH 4 is added, the nitrophenolate ion is illustrated by the NP (λ max =317 nm) absorption peak shifting to (λ max =400 nm).[44,45]. Over time, and after adding 2% Ag/g-C 3 N 4 / TiO 2 catalyst, an additional peak appeared at 300 nm, characteristic of PAP, accompanied by a decrease in the PNP peak. With increased reaction time to 20 minutes, there was a complete reduction of PNP to PAP. However, for the photocatalytic reaction, upon exposure to sunlight, as apparent in Fig.6 (b) , the conversion process accelerated significantly, with a complete reduction occurring after only 6.5 minutes with 2% Ag/TiO 2 /g-C 3 N 4 . However, the pseudo-first-order reaction model was applied to ascertain the kinetic parameters of both catalytic (see Fig. 7(a, c)) and photocatalytic reduction processes (see Fig. 7(b, d)) . The A/A 0 versus time and lnA/A 0 versus time graphs were generated for analysis. The plot of lnA/A 0 versus time emerges a straight line, suggesting that pseudo-first-order reaction kinetics govern the reduction process. Table S 1 illustrates a very sluggish kinetic rate for the individual TiO 2 /g-C 3 N 4 when no light is present. However, the kinetic rate constants of TiO₂/g-C₃N₄ with 2% Ag nanoparticles are superior to unmodified TiO₂/g-C₃N₄. It's interesting to note that when 4-NP was exposed to direct visible light, the conversion to 4-AP was markedly accelerated. For 2%Ag/TiO 2 /g-C 3 N 4 , the reduction process was completed in just 6.5 minutes under light, compared to 20 minutes in darkness. Consequently, the rate constant for the reduction under visible light was approximately 3times higher than in the dark reaction for 2%Ag/TiO 2 /g-C 3 N 4 . On the other hand, we evaluated the commercial TiO₂ (UV100, anatase; see XRD in Fig. S1 ) as a replacement for the TiO₂ used in our system. The results confirmed that the 2% Ag/TiO₂/g-C₃N₄ nanocomposite exhibited a photocatalytic rate approximately twice that of the commercial counterpart, 2% Ag/TiO₂ (A)/g-C₃N₄. Accordingly, we can say that 2%Ag/TiO 2 /g-C 3 N 4 was selected to be the optimized catalyst. This data implies that the created photocatalyst possesses greater (photo) catalytic efficiency compared to those reported in previously published work (see Table S 2) . 3.2.2. Photo ( Catalytic ) PNP reduction mechanism. The reduction of PNP using Ag/TiO 2 /g-C 3 N 4 was carried out, as previously mentioned, without light (catalytic reduction), and under visible light illumination (photocatalytic reduction). Thus, the mechanisms for both reactions should be investigated. For the catalytic reduction mechanism, the reduction depends on the adsorption, and the electron transfer process[46]. In detail, as shown in Fig. 8(a) , the reducing agent (BH 4 - ), and the substrate (PNP) are adsorbed onto the catalyst surface, TiO 2 /g-C 3 N 4 , followed by oxidation of (BH 4 - ) to produce borate ions and free electrons. These electrons have the ability to reduce PNPto PAP[46]. After loading Ag NPs, the PNP reduction rate increased more than 157 times compared to the reaction without Ag. This was explained by the fact that Ag NPs' surface formed active surface hydrogen species, which helped reduce PNP to PAP. Therefore, Ag NPs' existence makes an effective contribution, not only by transferring electrons to the substrate, but also by producing a powerful reducing agent (H 2 ) on its surface via the hydrolysis of BH 4 -. These hydrogen species assist in the reduction process and maintain catalyst activity by desorbing the product (PAP) from the catalyst surface[46,47]. For the photocatalytic mechanism, after exposure of Ag/gC 3 N 4 /TiO 2 catalyst to direct visible illumination, the photogenerated electron-hole pairs are produced, and contribute to the reduction process. Band edge positions for the valence band (VB) and conduction band (CB) of the Ag/gC 3 N 4 /TiO 2 nanoparticles were determined using the Mulliken electronegativity theory, using the subsequent calculation s (1, 2) : Here, E VB , E CB , and E e are the valence band, conduction band potentials, and the free electrons energy relative to the hydrogen electrode (4.5 eV), respectively [48]. Equation (3) is utilized to calculate the semiconductor's absolute electronegativity χ, where the individual atom numbers are denoted by a, b, and c. TiO₂ and g-C₃N₄ had (χ) values of 5.81 and 4.73, respectively. The positions of (CB) and (VB) for g-C 3 N₄ are -1.163 eV and 1.623 eV, respectively, whereas for TiO₂, they are -0.288 eV and 2.9 eV. When visible light strikes TiO₂/g-C₃N₄, photoexcitation generates electron-hole pairs. The electron transfer process within the heterojunction can follow multiple possible mechanisms. A : Type II mechanism, in this mechanism, photogenerated electrons are directly moved from the g-C 3 N 4 (CB) to that of TiO 2 as TiO 2 's CB (-0.288 eV) has a more positive potential than g-C 3 N 4 's (-1.163 eV). TiO 2 's VB has a greater potential (2.9 eV) than g-C 3 N 4 's (1.62 eV), hence the photogenerated holes in the TiO 2 VB move to g-C 3 N 4 VB. However, following this mechanism, the electrons in the TiO 2 CB are unable to reduce PNP to PAP, as the potential required for PNP/PAP conversion (-0.76 eV vs NHE) is more than TiO 2 's CB position (-0.288 eV) (see Fig. 8b) . Therefore, in this instance, the mechanism for type II charge transfer is ineffective. So, the reduction of PNP to PAP by TiO 2 /g-C 3 N 4 heterostructure will be explained by Z-scheme mechanism. B: Upon exposure of TiO 2 /g-C 3 N 4 to sunlight, the TiO 2 CB's generated electrons are transferred across the solid-solid interface to g-C 3 N 4 's VB, where they later combine with the g-C 3 N 4 's localized holes Fig. 8(b) . After that, the electrons in g-C 3 N 4 's VB will be stimulated and transfer to the CB and eventually to Ag NPs, because Ag possess a high electron storage capacity[49], electron-hole recombination is reduced (as subsequently shown by PL analysis ) which enhances photocatalytic activity for reducing PNP to PAP [50,51].Thus, it can be concluded that the Z-scheme mechanism, as opposed to the type II mechanism, can reduce PNP to PAP. A photoluminescence (PL) investigation was conducted to examine how 2%Ag/TiO 2 /g-C 3 N 4 accelerated the aptitude of photocatalysis to fully reduce PNP in comparison with other specimens, as illustrated in Fig.9 . The PL analysis investigates the electron/hole pair lifetime and aids in assessing the effectiveness of charge carrier separation within this photocatalyst. All samples were excited at 320 nm. The greater the peak intensity, the faster the electrons and holes combine, leading to lower photocatalytic activity. As shown in Fig.9 , pure TiO 2 does not exhibit any emission in the visible spectrum, which restricts its ability to catalyze reactions there. Conversely, for pure g-C 3 N 4 which exhibits a broad and intense peak at 452 nm, indicating that the photoinduced electrons and holes recombine quickly, which also restricts its capacity to catalyze [52]. However, the peak intensity at the same wavelength was clearly decreased by coupling g-C 3 N 4 with TiO 2 , indicating slower electron-hole recombination. The PL emission peak intensity was further reduced by adding varying concentrations of Ag NPs to TiO 2 /g-C 3 N 4 . The emission peak intensity dropped with increasing the concentration of Ag NPs. Furthermore, of the investigated photocatalysts with the least amount of Ag NPs, 2% Ag/TiO 2 /g-C 3 N 4 demonstrated the maximum photocatalytic efficiency. 4. Conclusion In this work, a biphasic TiO₂ (anatase/brookite) was deposited onto g-C₃N₄ using a simple impregnation method, followed by Ag nanoparticle loading via photodeposition to construct a Z-scheme photocatalyst. Structural and optical analyses confirmed successful Ag integration, enhanced visible light absorption, increased surface area, and improved charge carrier separation. Photocatalytic performance was evaluated by reducing nitrophenol (NP) to aminophenol (AP). The results showed that the 2% Ag/TiO₂/g-C₃N₄ nanocomposite demonstrated a photocatalytic rate nearly three times greater than that of the 0.5% Ag-loaded counterpart, double that of the composite based on commercial TiO₂ (2% Ag/TiO₂ (A)/g-C₃N₄), and substantially higher than the unmodified TiO₂/g-C₃N₄ system. These results highlight the composite’s strong potential for photocatalytic environmental applications. Abbreviations PNP – p -Nitrophenol PAP – p -Aminophenol TiO₂ – Titanium Dioxide g-C₃N₄ – Graphitic Carbon Nitride AgNPs – Silver Nanoparticles XRD – X-ray Diffraction XPS – X-ray Photoelectron Spectroscopy UV–Vis DRS – Ultraviolet–Visible Diffuse Reflectance Spectroscopy PL – Photoluminescence FT-IR – Fourier Transform Infrared Spectroscopy TEM – Transmission Electron Microscopy HR-TEM – High-Resolution Transmission Electron Microscopy SEM – Scanning Electron Microscopy EDX – Energy-Dispersive X-ray Spectroscopy BET – Brunauer–Emmett–Teller (Surface Area Analysis) DLS – Dynamic Light Scattering CB – Conduction Band VB – Valence Band ZP – Zeta Potential NHE – Normal Hydrogen Electrode Declarations Ethics and Consent to Participate All authors have approved the manuscript and agreed to submit it as an original research article for possible publication in this journal, the corresponding author would like to undertake that the manuscript is not under consideration by another journal. Consent for Publication Not applicable. Competing Interest The authors declare no competing interests. Author Contribution Conception and design: Hamza El-Hosainy, Maged El-Kemary; Development of methodology: Hamza El-Hosainy, Alaa A. Alhashash; Acquisition of data: Hamza El-Hosainy, Alaa A. Alhashash; Analysis and interpretation of data: Hamza El-Hosainy, Alaa A. Alhashash; Writing and review of the manuscript: Hamza El-Hosainy, Alaa A. Alhashash; Study supervision: Maged El-Kemary, Abd El-Motaleb M. Ramadan, Hamza El-Hosainy; Formal Analysis: Hamza El-Hosainy, Alaa A. Alhashash, Abd El-Motaleb M. Ramadan, Ezz-Elregal M. Ezz-Elregal, Rafat Tahway, Maged El-Kemary. All authors reviewed the manuscript. Funding Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB). Availability of data and materials The datasets generated or analyzed during this study are available from the corresponding author on reasonable request. Acknowledgments The authors gratefully acknowledge the facilities and support provided by the Institute of Nanoscience and Nanotechnology, Kafrelsheikh University. 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Supplementary Files SupplemntaryInformation.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 22 Jun, 2025 Reviews received at journal 22 Jun, 2025 Reviews received at journal 21 Jun, 2025 Reviewers agreed at journal 15 Jun, 2025 Reviewers agreed at journal 12 Jun, 2025 Reviewers agreed at journal 10 Jun, 2025 Reviewers agreed at journal 10 Jun, 2025 Reviewers agreed at journal 10 Jun, 2025 Reviewers agreed at journal 10 Jun, 2025 Reviewers invited by journal 10 Jun, 2025 Editor assigned by journal 06 Jun, 2025 Submission checks completed at journal 06 Jun, 2025 First submitted to journal 05 Jun, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6826016","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":469471520,"identity":"3c6fa8c0-2131-4e3f-9ffa-34a3dee8c389","order_by":0,"name":"Hamza El-Hosainy","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAklEQVRIiWNgGAWjYBACAwhlkQAiDzAw2AApxsYDRGiRgGlJA2lpIF4LEBxmgOrFDczZTyd/+FEhkcfPf/jh4cK283Zr2w8DbamxicalxbInd4NhzxmJYskZaQaHZ7bdTt52JhGo5VhabgMuhx3I3ZDA2yaRuOEGg8FhXqAWswNALYwNh3FrOf92w8G//4Bazh//ANRyLtns/EMCWm7kbmzmbQBqOZADsuWAndkNQrbceLuZWeaYROLMGTkFh3nOJSeY3QDakoDPL+dzN398U2OT2M9/fPNnnjI7e7Pz6Q8ffKixwakFFTCyMSSCVSYQpRwM/jDYE694FIyCUTAKRgoAAK1pbN+0sy/9AAAAAElFTkSuQmCC","orcid":"","institution":"Kafrelsheikh University","correspondingAuthor":true,"prefix":"","firstName":"Hamza","middleName":"","lastName":"El-Hosainy","suffix":""},{"id":469471521,"identity":"f2683da3-82c1-423c-bb6a-25afe7a95a2e","order_by":1,"name":"Alaa A. 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Ezz-Elregal","email":"","orcid":"","institution":"Ain-Shams University","correspondingAuthor":false,"prefix":"","firstName":"Ezz-Elregal","middleName":"M.","lastName":"Ezz-Elregal","suffix":""},{"id":469471524,"identity":"2af5a289-c300-4355-953c-140ecd9a8696","order_by":4,"name":"Rafat Tahway","email":"","orcid":"","institution":"Central Metallurgical Research and Development Institute, CMRDI","correspondingAuthor":false,"prefix":"","firstName":"Rafat","middleName":"","lastName":"Tahway","suffix":""},{"id":469471525,"identity":"75af4428-22b5-40a6-a906-130fae576507","order_by":5,"name":"Maged El-Kemary","email":"","orcid":"","institution":"Kafrelsheikh University","correspondingAuthor":false,"prefix":"","firstName":"Maged","middleName":"","lastName":"El-Kemary","suffix":""}],"badges":[],"createdAt":"2025-06-05 06:53:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6826016/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6826016/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84478424,"identity":"e4967103-7db1-42b0-88ff-38e4c336920f","added_by":"auto","created_at":"2025-06-12 12:07:28","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":123146,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of Ag/TiO₂/g-C₃N₄ synthesis.\u003c/p\u003e\n\u003cp\u003eA schematic diagram representing the synthesis strategy of the ternary Ag/TiO₂/g-C₃N₄ nanocomposite. The process includes impregnation of biphasic anatase/brookite TiO₂ onto g-C₃N₄, followed by photodeposition of Ag nanoparticles to form a Z-scheme photocatalyst with enhanced charge separation.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/94f307d492a3588f7dbdb346.png"},{"id":84479050,"identity":"af68aed0-dcf8-4838-a16b-77969c5d586a","added_by":"auto","created_at":"2025-06-12 12:15:28","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":99021,"visible":true,"origin":"","legend":"\u003cp\u003eStructural and optical properties of prepared materials.\u003c/p\u003e\n\u003cp\u003e(a) XRD patterns confirming the presence of anatase and brookite phases in TiO₂ and the characteristic peaks of g-C₃N₄. (b) FT-IR spectra showing functional groups and bonding in TiO₂, g-C₃N₄, and composites. (c) UV–Vis DRS showing absorption enhancement upon Ag loading. (d) Tauc plots used to calculate band gap energies, demonstrating a red shift in the visible range for Ag-loaded composites.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/b5be5018902615daa0d2c6e6.png"},{"id":84478425,"identity":"1971a04b-fed6-4e7c-925e-94c8725b411b","added_by":"auto","created_at":"2025-06-12 12:07:28","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":65962,"visible":true,"origin":"","legend":"\u003cp\u003eTextural properties and surface charge analysis.\u003c/p\u003e\n\u003cp\u003e(a) N₂ adsorption–desorption isotherms reveal mesoporosity and surface area variations among samples. (b) Pore size distribution curves indicate a more uniform structure in Ag/TiO₂/g-C₃N₄. (c) Zeta potential measurements show increased dispersion stability and surface charge due to Ag incorporation.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/b1f70782d2c49e6770ade7d3.png"},{"id":84478431,"identity":"4c3062d8-1060-416f-b4ae-6f17bec03599","added_by":"auto","created_at":"2025-06-12 12:07:28","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":85721,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of 2% Ag/TiO₂/g-C₃N₄.\u003c/p\u003e\n\u003cp\u003e(a) Survey scan showing elements present. (b) Ag 3d core level peaks confirm metallic silver. (c–f) High-resolution spectra of O 1s, Ti 2p, C 1s, and N 1s reveal oxidation states and chemical environments confirming successful formation of the composite.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/3cd3384eb503573900d345e6.png"},{"id":84478434,"identity":"30ce97d3-282c-47ee-8e0d-9fd8d58ff28b","added_by":"auto","created_at":"2025-06-12 12:07:28","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":738410,"visible":true,"origin":"","legend":"\u003cp\u003eMorphological and structural confirmation via TEM.\u003c/p\u003e\n\u003cp\u003e(a) TEM image showing TiO₂ well-distributed on g-C₃N₄. (b) HR-TEM image with corresponding SAED pattern confirming lattice planes of anatase, brookite, and g-C₃N₄. (c–d) HR-TEM of 2% Ag/TiO₂/g-C₃N₄ showing dispersed Ag nanoparticles and lattice spacing matching Ag (111) planes.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/c3a89dcc66325e85394f506c.png"},{"id":84478427,"identity":"95872371-e863-4be1-b5b7-7b11f5bd99c9","added_by":"auto","created_at":"2025-06-12 12:07:28","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":83369,"visible":true,"origin":"","legend":"\u003cp\u003eCatalytic and photocatalytic reduction of PNP.\u003c/p\u003e\n\u003cp\u003e(a) UV–Vis spectra showing PNP reduction to PAP under dark conditions. (b) Accelerated reduction under visible light with 2% Ag/TiO₂/g-C₃N₄. (c) Visual evidence of yellow-to-colorless transformation, confirming PAP formation.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/674f3610e8b6d4400010cd92.png"},{"id":84479058,"identity":"6f8d6a52-f3ba-4650-9787-dc8e02bc5819","added_by":"auto","created_at":"2025-06-12 12:15:28","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":99477,"visible":true,"origin":"","legend":"\u003cp\u003eKinetic analysis of PNP reduction.\u003c/p\u003e\n\u003cp\u003e(a, c) Plots of A/A₀ and ln(A/A₀) versus time under dark conditions show first-order kinetics. (b, d) Plots under sunlight indicate faster reduction rates. Data supports enhanced performance of Ag-loaded composites, particularly 2% Ag/TiO₂/g-C₃N₄.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/dc60a03c4225582275e4617f.png"},{"id":84478437,"identity":"803daa94-c2ee-486e-9075-89f50473f574","added_by":"auto","created_at":"2025-06-12 12:07:28","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":131051,"visible":true,"origin":"","legend":"\u003cp\u003eProposed reaction mechanisms for PNP reduction.\u003c/p\u003e\n\u003cp\u003e(a) In dark: catalytic reduction involves adsorption and electron transfer facilitated by Ag nanoparticles. (b) Under light: a Z-scheme mechanism explains efficient charge separation and electron migration, improving photocatalytic activity.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/db3f596c277be44929f15db4.png"},{"id":84478452,"identity":"7f93575a-5b17-4c02-acb3-2fc42b72c774","added_by":"auto","created_at":"2025-06-12 12:07:29","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":48059,"visible":true,"origin":"","legend":"\u003cp\u003ePhotoluminescence spectra for charge separation analysis.\u003c/p\u003e\n\u003cp\u003ePL spectra excited at 320 nm demonstrated reduced emission intensity with increasing Ag content. The 2% Ag/TiO₂/g-C₃N₄ shows the weakest emission, indicating suppressed charge recombination and enhanced photocatalytic efficiency.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/23adef4ccc45797d67248b2f.png"},{"id":84480334,"identity":"0a5340ac-c71e-4740-bf50-cae7af15c0a8","added_by":"auto","created_at":"2025-06-12 12:31:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2588051,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/1cfdc5cc-dd60-41f4-8141-4571703eaaa0.pdf"},{"id":84478429,"identity":"5f0caf35-108d-4cdb-a873-250fc51c1884","added_by":"auto","created_at":"2025-06-12 12:07:28","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":76201,"visible":true,"origin":"","legend":"","description":"","filename":"SupplemntaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6826016/v1/1d8980839e412d7ba3837fdd.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Facile Construction of a Ternary Ag/TiO₂/g-C₃N₄ Nanocomposite with Boosted Visible- Light Photocatalytic Activity","fulltext":[{"header":"1.Introduction","content":"\u003cp\u003eThe rapid growth of population and industry generates significant amounts of effluents with toxic heavy metals and organic pollutants, introducing them into the ecosystem and making water pollution one of the major environmental issues facing the world today [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Nitroarenes, particularly p-nitrophenol (PNP), are among the most hazardous contaminants present in wastewaters [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. PNP is used in several applications, including pesticides, petroleum refining, dyeing and various chemical industries [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The presence of this compound in water can pose serious health risks to humans such as eye burns, respiratory problems, and skin allergies. If ingested, it may also irritate the digestive tract and cause nausea, vomiting, and diarrhea.[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. As a result, developing efficient methods to eliminate these organic pollutants from water is crucial. Recently, there are a number of techniques that can be used, including physical methods such as filtration, adsorption and sedimentation[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], chemical methods like coagulation, photocatalytic degradation, ozonation, chemical precipitation and ion exchange[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and biological methods, including aerobic and anaerobic treatment[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Among these methods, the best alternative for traditional wastewater treatment methods is semiconductor heterogeneous photocatalysis. This is due to its capacity to transform solar energy considered the ultimate renewable energy source for powering activities on Earth into chemical energy[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], produce fewer toxic and harmful secondary pollutants, and remove a variety of contaminants from different media [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Numerous semiconductor nanomaterials, including BiVO\u003csub\u003e4\u003c/sub\u003e, Ag\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, ZnO, TiO\u003csub\u003e2\u003c/sub\u003e, SnO\u003csub\u003e2\u003c/sub\u003e, AlO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, have been extensively researched for their ability to remove water pollutants[\u003cspan additionalcitationids=\"CR12 CR13 CR14 CR15 CR16\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. However, TiO\u003csub\u003e2\u003c/sub\u003e has received the most research attention among these semiconductors and is found in three natural phases: brookite, anatase, and rutile [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. TiO\u003csub\u003e2\u003c/sub\u003e has many advantages such as non-toxicity, affordability, strong oxidizing power, remarkable photochemical stability, and environmentally favorable qualities [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The photocatalytic characteristics of TiO\u003csub\u003e2\u003c/sub\u003e are mainly attributed to its anatase phase due to its favorable band alignment, which provides a strong driving force for electron transfer to molecular oxygen. However, both anatase and brookite phases are considered more crucial for reducing carrier recombination rates, as the band alignment between these two TiO\u003csub\u003e2\u003c/sub\u003e isomorphs enhances overall performance[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Despite all these advantages, TiO\u003csub\u003e2\u003c/sub\u003e faces certain limitations, such as a broad gap between bands (3.2 eV) that restricts its absorbing ability to the UV range only, thereby reducing its photocatalytic efficiency and causing rapid electron-hole recombination. Overcoming these restrictions is through the metal deposition [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], non-metal doping [\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], or coupling with semiconductors, that have smaller bandgap energies, which allows absorption in the spectrum's visible region, and lowers the charge carriers recombination rate [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOn the other hand, graphitic carbon nitride (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e), a semiconductor that has recently gained popularity for a variety of uses, as it has substantial surface area, chemically stable nature, affordability, and strong adsorptive capabilities. It can be prepared through simple methods such as the thermal polymerization of rich nitrogen precursors like urea, melamine or dicyandiamide. Additionally, g-C₃N₄ demonstrates promising performance in photocatalysis owing to its remarkable capacity to absorb visible light at 460 nm and its modest energy band gap (2.7 eV) [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].A TiO\u003csub\u003e2\u003c/sub\u003e/C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e heterojunction formed by combining semiconductors with a broad (TiO\u003csub\u003e2\u003c/sub\u003e) and a narrow (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) band gap, can expand the absorption border to the visible light range while also improving charge carrier separation performance. [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. However, this heterojunction still has some drawbacks, such as fast charge recombination and reduced photocatalytic efficiency [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. To address this issue, doping or depositing TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e by noble metals has been proposed. The composite's photocatalytic efficiency of TiO\u003csub\u003e2\u003c/sub\u003e and C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e has frequently been enhanced after the photo-deposition of noble metals. For instance, Ag NPs can be used as a surface catalytic center for the photoreduction reaction and help prevent the charge recombination. These Ag NPs can capture the photogenerated electrons during photocatalysis process and release them to break down the contaminants [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. In this work, biphasic anatase/brookite TiO\u003csub\u003e2\u003c/sub\u003e was deposited onto g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e using an impregnation method. Following this, Ag nanoparticles were deposited onto TiO₂/g-C₃N₄ via photodeposition, promoting a Z-scheme charge transfer mechanism. The synthesized composite demonstrated strong photocatalytic activity when para-nitrophenol (PNP) is converted to para-aminophenol (PAP). The Z-scheme mechanism in the photocatalyst reduces charge carrier recombination and enhances redox potential, thereby boosting its photocatalytic performance.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cp\u003eTitanium tetraisopropoxide (Ti[OC\u003csub\u003e3\u003c/sub\u003eH\u003csub\u003e7\u003c/sub\u003e]\u003csub\u003e4\u003c/sub\u003e), and Pluronic (P123) were sourced from Sigma-Aldrich, Urea (CH\u003csub\u003e4\u003c/sub\u003eN\u003csub\u003e2\u003c/sub\u003eO) was acquired from Advent Company, Ethanol (C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eOH), and Methanol (CH\u003csub\u003e3\u003c/sub\u003eOH)were obtained from chem-lab Company, and Silver nitrate (AgNO\u003csub\u003e3\u003c/sub\u003e) was supplied by Merck. All chemicals were utilized just as it was delivered, without any additional processing.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Synthesis of biphasic anatase/brookite TiO\u003csub\u003e2\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eIn a standard synthesis process, utilizing 100 mL of distilled water, 3.5 g of Pluronic was submerged within a breaker of 250 mL and stirred at 80\u0026deg;C for 1 hour. While stirring, 20 mL of titanium isopropoxide was gradually introduced to form a colloidal sol, 0.2 M NaOH was then used to bring the pH to 8. To facilitate the hydrolysis reaction, the resulting blend was then put in an autoclave with Teflon liner and heat it over 15 hours to 110\u0026deg;C. Once the temperature has dropped to ambient temperature, the obtained gel underwent a 12-minute centrifugation at 10,000 rpm then rinsed 3 times with distilled water. Finally, 12 hours were spent drying the purified precipitate at 60\u0026deg;C, yielding the finished powder of TiO₂.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Preparation of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eA typical thermal polycondensation technique was used to synthesize the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e.[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The procedure was as follows: A muffle furnace was employed to heat a crucible containing 10 g of urea for 4 hours at 550\u0026deg;C with a ramp rate of 2\u0026deg;C per minute. Once it had cooled down to ambient temperature, a fine powder was made from the resulting yellow chunk for subsequent use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Formation of the TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nanocomposite\u003c/h2\u003e \u003cp\u003eTo form the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e/TiO\u003csub\u003e2\u003c/sub\u003e nanocomposite, a 1:1 weighing ratio of titania and graphitic carbon nitride was combined with 30 mL of ethanol in a 50 mL beaker. Following 12 hours of continuous stirring, the mixture underwent ultrasonic treatment for 30 minutes. Centrifugation was then utilized to separate the resulting precipitate for ten minutes at 10,000 rpm and subsequently air-dried at 60\u0026deg;C for a duration of 12 hours.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Synthesis of Ag NPs onTiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eheterojunction\u003c/h2\u003e \u003cp\u003eThe Ag(x %) /g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e/TiO\u003csub\u003e2\u003c/sub\u003e nanocomposite, with x\u0026thinsp;=\u0026thinsp;0.5, 1, 2 wt%, was produced through the process of photodeposition. Specifically, a calculated amount of AgNO\u003csub\u003e3\u003c/sub\u003e was mixed with 0.1 g of the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e/TiO\u003csub\u003e2\u003c/sub\u003e nanocomposite within a 50 mL beaker filled with 3 mL of methanol and 7 mL of distilled water. The mixture underwent stirring for three hours under light conditions (240 V, 500 W, and 6000 Lumen). Subsequently, Centrifugation of the solution was performed for 12 minutes at 10,000 rpm. The produced precipitate was washed 3times and let to air dry at 60\u0026deg;C for 12 hours.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Characterization\u003c/h2\u003e \u003cp\u003eThe materials' phase composition and crystallinity were analyzed by X-ray Diffractometry (XRD) with a Bruker D8 diffractometer, which features Cu-Kα radiation (λ\u0026thinsp;=\u0026thinsp;0.15406 nm) and a secondary monochromator. For looking into the surface's chemical constitution, X-ray Photoelectron Spectroscopy (XPS) was practiced out using a Thermo VG Multilab 2000 (England) in the 0\u0026ndash;4 keV energy range. The nanostructure\u0026rsquo;s size and morphology were assessed through transmission electron microscopy (TEM) using a JEOL-JEM-2100 (Tokyo, Japan) operating at 200 kV. Additionally, scanning electron microscopy (SEM) was employed for morphological analysis, utilizing an energy-dispersive X-ray (EDX) detector (S-3400 N II, Hitachi, Japan) integrated into a Sirion FEI microscope. For Optical properties, diffuse reflectance and absorbance spectra (UV-Vis DRS) using a JASCO V-770 spectrophotometer were employed to quantify it. To quantify photoluminescence (PL), data were gathered utilizing a JASCO FP8600 spectrofluorometer. Fourier transform infrared (FT-IR) spectroscopy was conducted via a JASCO FTIR-6800 within the 400\u0026ndash;4000 cm⁻\u0026sup1; range. The zeta potential was determined via dynamic light scattering (DLS) with a tool from Brookhaven Instruments (USA). Finally, the specific region of surface and size of pores dispersion were assessed by a Quantachrome analyzer (Nova Series, UK) via N₂ adsorption-desorption isotherms\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6. The Photo (catalytic) transformation of nitrophenol (NP) to aminophenol (AP)\u003c/h2\u003e \u003cp\u003eThe composite's photo-catalytic efficiency was tested through converting NP to AP during sun radiation and darkness. The reaction in dark, 2.8 mL of distilled water was combined with 40 \u0026micro;L of NP (0.01M) in a cuvette. Next, 80 \u0026micro;L of newly made NaBH\u003csub\u003e4\u003c/sub\u003e solution (0.5 M) has been provided. Upon adding NaBH\u003csub\u003e4\u003c/sub\u003e, we observed that the solution's color changed to bright yellow. After that, the previous mixture was supplemented with 10\u0026micro;L of (5 mg/mL) catalyst. During the reaction, we noticed yellow to colorless change in the solution's color. The reaction progress was tracked using (UV-Vis) spectroscopy. The photocatalytic process followed the same procedure but was carried out under direct sunlight.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003e\u003cstrong\u003e3.1. Ternary Ag/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e/TiO\u003csub\u003e2\u003c/sub\u003e nanocomposite characterization\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this research, a biphasic anatase/brookite TiO\u003csub\u003e2\u003c/sub\u003e was combined with g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e through a direct impregnation method. Following this, a photodeposition technique was employed to deposit nanoparticles of silver onto the TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nanocomposite, as displayed in \u003cstrong\u003eFig.1\u003c/strong\u003e. The materials\u0026apos; Phase arrangement and crystallinity were assessed by X-ray diffraction (XRD). The XRD patterns of TiO\u003csub\u003e2\u003c/sub\u003e, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, and 2% Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003ephotocatalysts are displayed in \u003cstrong\u003eFig. 2(a)\u003c/strong\u003e. Based on the findings, the bare TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles exhibited a combination of both anatase and brookite phases. The anatase phase of TiO₂ demonstrates XRD peaks at 2\u0026theta; = 25.2\u0026deg;, 37.8\u0026deg;, 47.9\u0026deg;, 54.0\u0026deg;, and 62.6\u0026deg; for planes (101), (004), (200), (105), and (204) (JCPDS 21-1271). On the other hand, the primary diffraction peak for the brookite phase of TiO\u003csub\u003e2\u003c/sub\u003e was identified at a 2\u0026theta; value of 30.8\u0026deg;, associated with the (121) crystal plane. Regarding to g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, a prominent and broad peak at 27.4\u003csup\u003eo\u003c/sup\u003e was identified, characteristic of the (002) pattern, while the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u0026apos;s in-plane repeating units were accountable for the (100) faint diffraction peak at 13\u003csup\u003eo\u003c/sup\u003e. [35]. Whereas The appearance of diffraction peaks for TiO\u003csub\u003e2\u003c/sub\u003e and g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003ein the TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003ecomposite sample indicates that the two materials were effectively combined, with a weak peak of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e at 27.4\u0026deg;.The 2% Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e XRD patterns did not exhibit any additional peaks, likely due to the minor concentration and high spread of Ag nanoparticles on the TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e composite\u0026apos;s surface.\u003c/p\u003e\n\u003cp\u003eOn the other hand, the chemical composition and specific functional groupings found within samples are ascertained via FT-IR spectroscopy. As illustrated in \u003cstrong\u003eFig. 2(b)\u003c/strong\u003e, the main peaks for pure TiO\u003csub\u003e2\u003c/sub\u003e observed at 400\u0026ndash;700cm\u003csup\u003e\u0026minus;1\u003c/sup\u003eare designated for the modes of Ti-O-Ti and Ti-O bending vibration [36] . The peaks at around 1650 and 3000\u0026ndash;3500 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e are related to bending and stretching vibrations of \u0026nbsp; hydroxyl groups[37]. In g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u0026apos;s FT-IR spectrum, the distinctive breathing modes of tri-s-triazine units are responsible for the 812 cm\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003epeak. The CN heterocycles\u0026apos; stretching vibrations are responsible for the strong absorption band within1200 and1700 cm\u003csup\u003e-1\u003c/sup\u003e. The vibrational stretching modes of terminal N-H and O-H were identified as the cause of the large peak at 3000-3650 cm\u003csup\u003e-1\u003c/sup\u003e.[28].All the absorption peaks mentioned above were shown in TiO\u003csub\u003e2\u003c/sub\u003e/ g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and without changes, demonstrating that during the formation of the composite, neither the structure of TiO\u003csub\u003e2\u003c/sub\u003e nor that of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was destroyed. Additionally, all the primary distinctive TiO\u003csub\u003e2\u003c/sub\u003e and g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e peaks were apparent in the Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eternary composite, confirming their coexistence.\u003c/p\u003e\n\u003cp\u003eDiffuse reflectance spectroscopy (DRS) is essential for evaluating the optical properties and absorption profiles of samples. As illustrated in \u003cstrong\u003eFig. 2(c)\u003c/strong\u003e, TiO\u003csub\u003e2\u003c/sub\u003e shows an absorption edge in the (UV) range at around 390 nm, which is equivalent to an indirect band-gap energy (Eg) of 3.2 eV, as indicated in \u003cstrong\u003eFig. 2(d)\u0026nbsp;\u003c/strong\u003e[38-40]. In contrast, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e exhibits an absorbing edge in the visible range at 440 nm and a band-gap energy of 2.79 eV. When g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e is combined with TiO\u003csub\u003e2\u003c/sub\u003e, the absorption edge moves into the visible spectrum at 460 nm, and the band gap energy becomes 2.74 eV. After depositing varying amounts of Ag nanoparticles onto the TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e surface, a noticeable red shift in the absorption edge towards the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e range was observed. The 2% Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e sample demonstrated an optimal band-gap energy of 2.75 eV as displayed in \u003cstrong\u003eFig. 2(d)\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003eTo investigate the texture, porosity, and surface area of the prepared samples, Pore size distribution curves were plotted alongside N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms. The typical mesoporous structure of TiO₂ with a moderate surface area is shown in \u003cstrong\u003eFig. 3(a)\u003c/strong\u003e, as indicated by the adsorption-desorption isotherm and the hysteresis loop\u0026apos;s presence, which suggests cylindrical pores. On the other hand, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eexhibits a lower surface area due to its layered structure, with fewer pores compared to TiO₂. Thus, Pure TiO\u003csub\u003e2\u003c/sub\u003e has a greater BET surface area (190.7 m\u003csup\u003e2\u003c/sup\u003e/g) than g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (114 m\u003csup\u003e2\u003c/sup\u003e/g). However, incorporating Ag into the TiO₂/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e composite slightly increases the surface area (118 m\u0026sup2;/g) compared to g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, enhancing the adsorption capacity as a result of the components\u0026apos; synergistic effect. The hysteresis loop in the Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e composite suggests the presence of mesopores, while the sharp rise in adsorption at higher P/P₀ values indicates capillary condensation within the pores. Furthermore, distributions of pore size in TiO₂, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nanocomposites exhibit distinct characteristics as shown in \u003cstrong\u003eFig. 3(b)\u003c/strong\u003e. TiO₂ displays a Pore size on average of approximately 6.1 nm, while both g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u0026nbsp;\u003c/sub\u003ephotocatalysts have average pore sizes around 5.2 nm. Notably, the pore size distribution peak for TiO₂ is broader compared to the sharper peaks observed for g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. This broader peak indicates a wider range of pore sizes in TiO₂, suggesting a more heterogeneous pore structure. In contrast, the narrower peaks for g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u0026nbsp;\u003c/sub\u003eand Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u0026nbsp;\u003c/sub\u003esamples imply more uniform pore size distributions. These differences in pore size uniformity can significantly influence the materials\u0026apos; surface areas and, consequently, their photocatalytic performances. A more uniform pore size distribution, as seen in Ag/TiO₂/g-C₃N₄, typically facilitates better adsorption and diffusion of reactant molecules, potentially enhancing photocatalytic efficiency.\u003c/p\u003e\n\u003cp\u003eThe zeta potential analysis, shown in \u003cstrong\u003eFig.3(c)\u003c/strong\u003e, highlights the surface charge differences among TiO₂, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, and the Ag/TiO₂/ g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003ephotocatalysts. TiO₂ exhibits a zeta potential approximately -24.70 mV, suggesting good stability in dispersion due to electrostatic repulsion. g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eshows a less negative zeta potential of around -18.33 mV, indicating moderate surface charge and stability in colloidal form. Adding silver to the TiO₂/ g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e composite causes a shift in the zeta potential toward a more negative value, around -41.70 mV. This shift indicates a change in surface properties and charge distribution upon nanoparticle incorporation, confirming the increase in the nanocomposite\u0026apos;s dispersion stability and catalytic efficiency in aqueous environments.\u003c/p\u003e\n\u003cp\u003eConversely, the oxidation states and chemical contents of the produced samples were ascertained using XPS analysis. The elements Ti, O, N, C, and Ag are found in the Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e XPS survey spectra \u003cstrong\u003e(see Fig.4 (a))\u003c/strong\u003e. The Ag (3d) peaks in \u003cstrong\u003eFig. 4(b)\u0026nbsp;\u003c/strong\u003eat 368.15 and 374.11 eV they belong to Ag3d\u003csub\u003e5/2\u003c/sub\u003eand Ag3d\u003csub\u003e3/2\u003c/sub\u003eof metallic Ag, respectively[41] . O\u003csup\u003e2-\u003c/sup\u003e and O-H bonds are illustrated by the peaks in the O1s spectra, \u003cstrong\u003eFig. 4(c)\u003c/strong\u003e, at 529.8 and 531 eV, respectively [42].According to \u003cstrong\u003eFig. 4(d)\u003c/strong\u003e, the identified peaks at 458.5 and 464 eV correspond to Ti2p\u003csub\u003e3/2\u003c/sub\u003e and Ti2p\u003csub\u003e1/2\u003c/sub\u003e, respectively. In\u003cstrong\u003e\u0026nbsp;Fig. 4(e)\u003c/strong\u003e, the XPS spectra of C (1s) revealed two distinct peaks at 284.75 eV and 288 eV, In accordance with sp\u0026sup2;-hybridized carbon (C\u0026minus;C) and sp\u0026sup2;-bonded carbon (N\u0026minus;C=N), respectively. Similarly, \u003cstrong\u003eFig. 4f\u003c/strong\u003e displays three primary N (1s) peaks at 398.56 eV, 400.16 eV, and 401.4 eV associated with sp\u0026sup2;-hybridized nitrogen (C=N\u0026minus;C), sp\u0026sup3;-hybridized tertiary nitrogen (N-(C)₃), and terminal amino functional groups containing a single hydrogen atom (C\u0026minus;N\u0026minus;H) within heptazine rings, respectively [43]. Based on these findings, thus, it may be stated that the Ag/TiO₂/g-C₃N₄ nanocomposite was successfully synthesized with excellent structural properties.\u003c/p\u003e\n\u003cp\u003eThe TEM images illustrate the morphological features of the formed nanocomposites as indicated in \u003cstrong\u003eFig. 5\u003c/strong\u003e. The combination of TiO₂/g-C₃N₄ is depicted in \u003cstrong\u003eFig. 5(a)\u003c/strong\u003e, revealing a homogeneous spread of TiO₂ nanoparticles on the g-C₃N₄ matrix, which is indicative of successful heterojunction formation. The HR-TEM image (Fig. 5(b)) of the TiO₂/g-C₃N₄ nanocomposite revealed distinct lattice fringes corresponding to both anatase and brookite phases of TiO₂, as well as g-C₃N₄. Specifically, lattice spacings of 0.35 nm and 0.29 nm were attributed to the (101) plane of anatase and the (121) plane of brookite, respectively, confirming the coexistence of biphasic TiO₂. Additionally, the presence of g-C₃N₄ was identified by the lattice spacing of 0.32 nm, corresponding to the (002) plane. These observations collectively indicate the successful formation of a heterojunction structure. \u003cstrong\u003eFig. 5(c)\u0026nbsp;\u003c/strong\u003eshow the HRTEM of 2% Ag/TiO₂/g-C₃N₄ nanocomposite, where Ag nanoparticles are observed to be spread equally across the TiO₂/g-C₃N₄ surface, suggesting effective Ag\u0026apos;s inclusion in the composite structure. Image \u003cstrong\u003eFig.5(d)\u003c/strong\u003e provides (HRTEM) image of the 2% Ag/TiO₂/g-C₃N₄ sample, displaying the presence of Ag NPs as confirmed by the lattice spacing of the 0.23 nm (111). These observations suggest the successful formation of the Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e nanocomposite with potential for higher photocatalytic performance due to improved charge separation and light absorption facilitated by Ag.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2. (\u003c/strong\u003e\u003cstrong\u003ePhoto\u003c/strong\u003e\u003cstrong\u003e)\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;catalytic behavior of the prepared photocatalysts\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2.1. Conversion of para-nitrophenol (PNP) to para-aminophenol (PAP)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo assess the prepared samples\u0026apos; (photo) catalytic behavior, PNP was reduced to PAP by employing NaBH\u003csub\u003e4\u003c/sub\u003e as the reaction\u0026apos;s reducing agent. For catalytic reaction, as shown in \u003cstrong\u003eFig. 6(a)\u003c/strong\u003e, at zero time, when NaBH\u003csub\u003e4\u003c/sub\u003e is added, the nitrophenolate ion is illustrated by the NP (\u0026lambda;\u003csub\u003emax\u003c/sub\u003e=317 nm) absorption peak shifting to (\u0026lambda;\u003csub\u003emax\u003c/sub\u003e=400 nm).[44,45]. Over time, and after adding 2% Ag/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e/ TiO\u003csub\u003e2\u003c/sub\u003e catalyst, an additional peak appeared at 300 nm, characteristic of PAP, accompanied by a decrease in the PNP peak. With increased reaction time to 20 minutes, there was a complete reduction of PNP to PAP. However, for the photocatalytic reaction, upon exposure to sunlight, as apparent in \u003cstrong\u003eFig.6 (b)\u003c/strong\u003e, the conversion process accelerated significantly, with a complete reduction occurring after only 6.5 minutes with 2% Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. However, the pseudo-first-order reaction model was applied to ascertain the kinetic parameters of both catalytic \u003cstrong\u003e(see Fig. 7(a, c))\u003c/strong\u003e and photocatalytic reduction processes \u003cstrong\u003e(see Fig. 7(b, d))\u003c/strong\u003e. The A/A\u003csub\u003e0\u003c/sub\u003e versus time and lnA/A\u003csub\u003e0\u003c/sub\u003e versus time graphs were generated for analysis. The plot of lnA/A\u003csub\u003e0\u003c/sub\u003e versus time emerges a straight line, suggesting that pseudo-first-order reaction kinetics govern the reduction process. \u003cstrong\u003eTable\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eS\u003c/strong\u003e\u003cstrong\u003e1\u0026nbsp;\u003c/strong\u003eillustrates a very sluggish kinetic rate for the individual TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e when no light is present. However, the kinetic rate constants of TiO₂/g-C₃N₄ with 2% Ag nanoparticles are superior to unmodified TiO₂/g-C₃N₄.\u0026nbsp;It\u0026apos;s interesting to note that when 4-NP was exposed to direct visible light, the conversion to 4-AP was markedly accelerated. For 2%Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, the reduction process was completed in just 6.5 minutes under light, compared to 20 minutes in darkness. Consequently, the rate constant for the reduction under visible light was approximately 3times higher than in the dark reaction for 2%Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e.\u0026nbsp;On the other hand, we evaluated the commercial TiO₂ (UV100, anatase; see XRD in \u003cstrong\u003eFig. S1\u003c/strong\u003e) as a replacement for the TiO₂ used in our system. The results confirmed that the 2% Ag/TiO₂/g-C₃N₄ nanocomposite exhibited a photocatalytic rate approximately twice that of the commercial counterpart, 2% Ag/TiO₂ (A)/g-C₃N₄. Accordingly, we can say that\u0026nbsp;2%Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u0026nbsp;\u003c/sub\u003ewas selected to be the optimized catalyst. This data implies that the created photocatalyst possesses greater (photo) catalytic efficiency compared to those reported in previously published work \u003cstrong\u003e(see Table\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eS\u003c/strong\u003e\u003cstrong\u003e2)\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2.2. Photo\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;(\u003c/strong\u003e\u003cstrong\u003eCatalytic\u003c/strong\u003e\u003cstrong\u003e)\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;PNP reduction mechanism.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe reduction of PNP using Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was carried out, as previously mentioned, without light (catalytic reduction), and under visible light illumination (photocatalytic reduction). Thus, the mechanisms for both reactions should be investigated. For the catalytic reduction mechanism, the reduction depends on the adsorption, and the electron transfer process[46]. In detail, as shown in \u003cstrong\u003eFig. 8(a)\u003c/strong\u003e, the reducing agent (BH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e), and the substrate (PNP) are adsorbed onto the catalyst surface, TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, followed by oxidation of (BH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e) to produce borate ions and free electrons. These electrons have the ability to reduce PNPto PAP[46]. After loading Ag NPs, the PNP reduction rate increased more than 157 times compared to the reaction without Ag. This was explained by the fact that Ag NPs\u0026apos; surface formed active surface hydrogen species, which helped reduce PNP to PAP. \u0026nbsp;Therefore, Ag NPs\u0026apos; existence makes an effective contribution, not only by transferring electrons to the substrate, but also by producing a powerful reducing agent (H\u003csub\u003e2\u003c/sub\u003e) on its surface via the hydrolysis of BH\u003csub\u003e4\u003c/sub\u003e-. These hydrogen species assist in the reduction process and maintain catalyst activity by desorbing the product (PAP) from the catalyst surface[46,47].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFor the photocatalytic mechanism, after exposure of Ag/gC\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e/TiO\u003csub\u003e2\u003c/sub\u003e catalyst to direct visible illumination, the photogenerated electron-hole pairs are produced, and contribute to the reduction process. Band edge positions for the valence band (VB) and conduction band (CB) of the Ag/gC\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e/TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles were determined using the Mulliken electronegativity theory, using the subsequent calculation\u003cstrong\u003es (1, 2)\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003e\u003cimg 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\" width=\"397\" height=\"171\"\u003e\u003c/p\u003e\n\u003cp\u003eHere, E\u003csub\u003eVB\u003c/sub\u003e, E\u003csub\u003eCB\u003c/sub\u003e, and E\u003csub\u003ee\u003c/sub\u003e are the valence band, conduction band potentials, and the free electrons energy relative to the hydrogen electrode (4.5 eV), respectively [48]. Equation \u003cstrong\u003e(3)\u003c/strong\u003e is utilized to calculate the semiconductor\u0026apos;s absolute electronegativity \u0026chi;, where the individual atom numbers are denoted by a, b, and c. TiO₂ and g-C₃N₄ had (\u0026chi;) values of 5.81 and 4.73, respectively. The positions of (CB) and (VB) for g-C\u003csub\u003e3\u003c/sub\u003eN₄ are -1.163 eV and 1.623 eV, respectively, whereas for TiO₂, they are -0.288 eV and 2.9 eV. When visible light strikes TiO₂/g-C₃N₄, photoexcitation generates electron-hole pairs. The electron transfer process within the heterojunction can follow multiple possible mechanisms.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eA\u003c/strong\u003e: Type II mechanism, in this mechanism, photogenerated electrons are directly moved from the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (CB) to that of TiO\u003csub\u003e2\u003c/sub\u003e as TiO\u003csub\u003e2\u003c/sub\u003e\u0026apos;s CB (-0.288 eV) has a more positive potential than g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u0026apos;s (-1.163 eV). TiO\u003csub\u003e2\u003c/sub\u003e\u0026apos;s VB has a greater potential (2.9 eV) than g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u0026apos;s (1.62 eV), hence the photogenerated holes in the TiO\u003csub\u003e2\u003c/sub\u003e VB move to g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e VB. However, following this mechanism, the electrons in the TiO\u003csub\u003e2\u003c/sub\u003e CB are unable to reduce PNP to PAP, as the potential required for PNP/PAP conversion (-0.76 eV vs NHE) is more than TiO\u003csub\u003e2\u003c/sub\u003e\u0026apos;s CB position (-0.288 eV)\u0026nbsp;\u003cstrong\u003e(see Fig. 8b)\u003c/strong\u003e. Therefore, in this instance, the mechanism for type II charge transfer is ineffective.\u003c/p\u003e\n\u003cp\u003eSo, the reduction of PNP to PAP by TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e heterostructure will be explained by Z-scheme mechanism.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eB:\u0026nbsp;\u003c/strong\u003eUpon exposure of TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u0026nbsp;\u003c/sub\u003eto sunlight, the TiO\u003csub\u003e2\u003c/sub\u003e CB\u0026apos;s generated electrons are transferred across the solid-solid interface to g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u0026apos;s VB, where they later combine with the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u0026apos;s localized holes \u003cstrong\u003eFig. 8(b)\u003c/strong\u003e. After that, the electrons in g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u0026apos;s VB will be stimulated and transfer to the CB and eventually to Ag NPs, because Ag possess a high electron storage capacity[49], electron-hole recombination is reduced \u003cstrong\u003e(as subsequently shown \u0026nbsp;by PL analysis )\u003c/strong\u003e which enhances photocatalytic activity for reducing PNP to PAP [50,51].Thus, it can be concluded that the Z-scheme mechanism, as opposed to the type II mechanism, can reduce PNP to PAP.\u003c/p\u003e\n\u003cp\u003eA photoluminescence (PL) investigation was conducted to examine how 2%Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e accelerated the aptitude of photocatalysis to fully reduce PNP in comparison with other specimens, as illustrated in \u003cstrong\u003eFig.9\u003c/strong\u003e. The PL analysis investigates the electron/hole pair lifetime and aids in assessing the effectiveness of charge carrier separation within this photocatalyst. All samples were excited at 320 nm. The greater the peak intensity, the faster the electrons and holes combine, leading to lower photocatalytic activity. As shown in \u003cstrong\u003eFig.9\u003c/strong\u003e, pure TiO\u003csub\u003e2\u003c/sub\u003edoes not exhibit any emission in the visible spectrum, which restricts its ability to catalyze reactions there. Conversely, for pure g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e which exhibits a broad and intense peak at 452 nm, indicating that the photoinduced electrons and holes recombine quickly, which also restricts its capacity to catalyze [52]. However, the peak intensity at the same wavelength was clearly decreased by coupling g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with TiO\u003csub\u003e2\u003c/sub\u003e, indicating slower electron-hole recombination. The PL emission peak intensity was further reduced by adding varying concentrations of Ag NPs to TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. The emission peak intensity dropped with increasing the concentration of Ag NPs. Furthermore, of the investigated photocatalysts with the least amount of Ag NPs, 2% Ag/TiO\u003csub\u003e2\u003c/sub\u003e/g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e demonstrated the maximum photocatalytic efficiency.\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn this work, a biphasic TiO₂ (anatase/brookite) was deposited onto g-C₃N₄ using a simple impregnation method, followed by Ag nanoparticle loading via photodeposition to construct a Z-scheme photocatalyst. Structural and optical analyses confirmed successful Ag integration, enhanced visible light absorption, increased surface area, and improved charge carrier separation. Photocatalytic performance was evaluated by reducing nitrophenol (NP) to aminophenol (AP). The results showed that the 2% Ag/TiO₂/g-C₃N₄ nanocomposite demonstrated a photocatalytic rate nearly three times greater than that of the 0.5% Ag-loaded counterpart, double that of the composite based on commercial TiO₂ (2% Ag/TiO₂ (A)/g-C₃N₄), and substantially higher than the unmodified TiO₂/g-C₃N₄ system. These results highlight the composite\u0026rsquo;s strong potential for photocatalytic environmental applications.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cstrong\u003ePNP\u003c/strong\u003e \u0026ndash; \u003cem\u003ep\u003c/em\u003e-Nitrophenol\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePAP\u003c/strong\u003e \u0026ndash; \u003cem\u003ep\u003c/em\u003e-Aminophenol\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTiO₂\u003c/strong\u003e \u0026ndash; Titanium Dioxide\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eg-C₃N₄\u003c/strong\u003e \u0026ndash; Graphitic Carbon Nitride\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAgNPs\u003c/strong\u003e \u0026ndash; Silver Nanoparticles\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eXRD\u003c/strong\u003e \u0026ndash; X-ray Diffraction\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eXPS\u003c/strong\u003e \u0026ndash; X-ray Photoelectron Spectroscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eUV\u0026ndash;Vis DRS\u003c/strong\u003e \u0026ndash; Ultraviolet\u0026ndash;Visible Diffuse Reflectance Spectroscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePL\u003c/strong\u003e \u0026ndash; Photoluminescence\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFT-IR\u003c/strong\u003e \u0026ndash; Fourier Transform Infrared Spectroscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTEM\u003c/strong\u003e \u0026ndash; Transmission Electron Microscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHR-TEM\u003c/strong\u003e \u0026ndash; High-Resolution Transmission Electron Microscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSEM\u003c/strong\u003e \u0026ndash; Scanning Electron Microscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEDX\u003c/strong\u003e \u0026ndash; Energy-Dispersive X-ray Spectroscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBET\u003c/strong\u003e \u0026ndash; Brunauer\u0026ndash;Emmett\u0026ndash;Teller (Surface Area Analysis)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDLS\u003c/strong\u003e \u0026ndash; Dynamic Light Scattering\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCB\u003c/strong\u003e \u0026ndash; Conduction Band\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eVB\u003c/strong\u003e \u0026ndash; Valence Band\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eZP\u003c/strong\u003e \u0026ndash; Zeta Potential\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNHE\u003c/strong\u003e \u0026ndash; Normal Hydrogen Electrode\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics and Consent to Participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors have approved the manuscript and agreed to submit it as an original research article for possible publication in this journal, the corresponding author would like to undertake that the manuscript is not under consideration by another journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for Publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interest \u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConception and design: Hamza El-Hosainy, Maged El-Kemary; Development of methodology: Hamza El-Hosainy, Alaa A. Alhashash; Acquisition of data: Hamza El-Hosainy, Alaa A. Alhashash; Analysis and interpretation of data: Hamza El-Hosainy, Alaa A. Alhashash; Writing and review of the manuscript: Hamza El-Hosainy, Alaa A. Alhashash; Study supervision: Maged El-Kemary, Abd El-Motaleb M. Ramadan, Hamza El-Hosainy; Formal Analysis: Hamza El-Hosainy, Alaa A. Alhashash, Abd El-Motaleb M. Ramadan, Ezz-Elregal M. Ezz-Elregal, Rafat Tahway, Maged El-Kemary. All authors reviewed the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOpen access funding provided by The Science, Technology \u0026amp; Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated or analyzed during this study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge the facilities and support provided by the Institute of Nanoscience and Nanotechnology, Kafrelsheikh University.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAziz KHH, Mustafa FS, Omer KM, Hama S, Hamarawf RF, Rahman KOJRa (2023) Heavy metal pollution in the aquatic environment: efficient and low-cost removal approaches to eliminate their toxicity: a review. 13 (26):17595-17610\u003c/li\u003e\n\u003cli\u003eIbrahim I, Ali IO, Salama TM, Bahgat A, Mohamed MMJACBE (2016) Synthesis of magnetically recyclable spinel ferrite (MFe2O4, M= Zn, Co, Mn) nanocrystals engineered by sol gel-hydrothermal technology: High catalytic performances for nitroarenes reduction. 181:389-402\u003c/li\u003e\n\u003cli\u003eWei Z, Li Y, Dou L, Ahmad M, Zhang HJAANM (2019) Cu3\u0026ndash;x Ni x Al-layered double hydroxide-reduced graphene oxide nanosheet array for the reduction of 4-nitrophenol. 2 (4):2383-2396\u003c/li\u003e\n\u003cli\u003eTeimouri M, Khosravi-Nejad F, Attar F, Saboury AA, Kostova I, Benelli G, Falahati M (2018) Gold nanoparticles fabrication by plant extracts: synthesis, characterization, degradation of 4-nitrophenol from industrial wastewater, and insecticidal activity \u0026ndash; A review. 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Detailed physicochemical characterizations confirmed the successful immobilization of Ag nanoparticles on the TiO₂/g-C₃N₄ surface, contributing to a significantly enhanced surface area, broadened visible light absorption, and improved charge carrier separation. The photocatalytic performance of the resulting nanocomposites was evaluated through the reduction of p-nitrophenol (PNP) to p-aminophenol (PAP), revealing a remarkable enhancement in activity with increasing Ag content. Notably, the 2% Ag/TiO₂/g-C₃N₄ nanocomposite exhibited a photocatalytic rate approximately 3 times higher than that of 0.5% Ag/TiO₂/g-C₃N₄, twice that of 2% Ag/TiO₂ (commercial)/g-C₃N₄, and significantly superior to bare TiO₂/g-C₃N₄. The outstanding photocatalytic efficiency of the 2% Ag/TiO₂/g-C₃N₄ system is attributed to its superior light-harvesting ability and efficient charge separation via a Z-scheme mechanism. These findings present a promising and scalable strategy for engineering advanced ternary nanocomposite photocatalysts with enhanced environmental remediation capabilities.\u003c/p\u003e","manuscriptTitle":"Facile Construction of a Ternary Ag/TiO₂/g-C₃N₄ Nanocomposite with Boosted Visible- Light Photocatalytic Activity","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-12 12:07:23","doi":"10.21203/rs.3.rs-6826016/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-06-22T09:55:43+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-22T09:30:56+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-21T09:06:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"57540020152318320164956827003937672421","date":"2025-06-16T00:36:08+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"68418074713644249794304218652180778201","date":"2025-06-12T11:31:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"31583442878354717770207469123770029394","date":"2025-06-10T23:10:27+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"131797922178284102975297529100201704547","date":"2025-06-10T20:18:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"260674177992408743183244856021054073387","date":"2025-06-10T18:09:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"158859511083991507753668172877167056005","date":"2025-06-10T11:44:54+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-10T10:58:31+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-06T10:51:27+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-06T10:45:42+00:00","index":"","fulltext":""},{"type":"submitted","content":"Catalysis Letters","date":"2025-06-05T06:38:37+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"catalysis-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Catalysis Letters](https://link.springer.com/journal/10562)","snPcode":"10562","submissionUrl":"https://submission.springernature.com/new-submission/10562/3","title":"Catalysis Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"346539a5-8c29-4e06-b76d-6e37300c2b88","owner":[],"postedDate":"June 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-07-20T15:53:31+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-12 12:07:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6826016","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6826016","identity":"rs-6826016","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}