Hydrochar-Supported Nickel-Cobalt Selenide Electrocatalyst for Enhanced Oxygen Evolution Reaction Performance

Hydrochar-Supported Nickel-Cobalt Selenide Electrocatalyst for Enhanced Oxygen Evolution Reaction Performance | 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 Article Hydrochar-Supported Nickel-Cobalt Selenide Electrocatalyst for Enhanced Oxygen Evolution Reaction Performance Joaquin Nathaniel A. Perez, Chris Ivan B. Sungcang, Patricia Isabel R. Soriano, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7450657/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 12 You are reading this latest preprint version Abstract This study explores the development and characterization of a nickel-cobalt selenide (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) electrocatalyst supported on hydrochar and nickel foam for the oxygen evolution reaction (OER) in alkaline water electrolysis. NiCoSe is synthesized through electrodeposition and subsequently dispersed on hydrochar. The NiCoSe/hydrochar is drop cast on a nickel foam substrate to serve as the anode. The electrocatalyst is characterized through SEM-EDS, XRD, and FTIR. The activity and stability are evaluated using CV, LSV, and EIS. XRD patterns show the formation of the mixed metal selenides, while SEM micrographs reveal the presence of microstructures that enhance the surface area of the catalyst. Elemental mapping of the NiCoSe/hydrochar shows the uniform distribution of Ni, Co, and Se. The synthesized catalyst (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) was found to deliver a current density of 10 mA-cm -2 at an overpotential of 295.85 mV. Compared to the Ni foam alone, this composition shows a substantial improvement in the electrocatalytic activity, likely due to the reconfiguration of the electronic structure of nickel with the presence of cobalt. The presence of hydrochar contributes to a 6.55% reduction in the overpotential at 10 mA-cm -2 , highlighting its potential as a carbon support for dispersing the electrocatalyst and allowing for greater exposure of the active sites. A low Tafel slope of 72.15 mV-dec -1 further indicates high electrocatalytic activity, aligning with the performance of other Ni x Co y Se z electrocatalysts. This study demonstrates that nickel-cobalt selenide can effectively lower the high overpotential of the OER, although further enhancement is needed in the conductivity of hydrochar. Physical sciences/Chemistry Physical sciences/Energy science and technology Physical sciences/Materials science Nickel-Cobalt Selenide Hydrochar Support Oxygen Evolution Reaction Overpotential Reduction Transition Metal Chalcogenides Electrocatalysis Green Hydrogen Production Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction In 2023, approximately 30% of the total energy supply was derived from renewable sources. The growth of solar and wind energy is projected to bring up the total renewable energy share to 46% 1 . However, the variability and lack of storage capacity for solar and wind-based energy hinder its ability to decarbonize the transport industry and necessitate the development of storage technology that is versatile for other important industries 2 . Efforts to address these issues are emphasized by growing trends to explore the use of hydrogen fuel as a clean and reliable energy carrier for future energy demand 3 . Green hydrogen may be produced through the electrolysis of water, but a common problem with these systems is the slow kinetics of the oxygen evolution reaction (OER). A high overpotential causes the reaction to proceed non-spontaneously. Electrocatalysts can be used to remedy the high OER overpotential, but common noble metal catalysts are expensive and not readily available 4 . This has paved the way for the use of more cost-effective transition metal chalcogenides (TMCs). Some examples include nickel-cobalt selenide catalysts, which exhibit strong electrocatalytic abilities like noble metal catalysts. However, its relatively low electric conductivity and active sites require the use of support materials to improve its performance 5 . The emergence of carbon-based supports presents a renewable, ubiquitous, and effective method to support TMCs. One such support is hydrochar, which may be derived from a wide range of biomass sources to create a low-cost carbon-based material that can be used to improve the dispersion of TMCs and their overall electrocatalytic activity. The sluggish kinetics of the OER result in high overpotential, requiring the use of catalysts to improve reaction rates. Pt, Ni, and IrO x catalysts have been examined previously. Pt-based catalysts are greatly effective for the oxygen reduction reaction (ORR) but degrade quickly in OER, limiting their long-term stability 6,7 . Nickel oxides are inherently less active but exhibit improved performance when doped with Fe. They create NiFeO x compounds with high turnover frequency 8,9 . However, the debate over whether Ni or Fe functions as the primary active site remains. IrO x -based compounds demonstrate excellent OER activity and stability, but their high cost and scarcity limit large-scale application 10,11 . To address these limitations, bimetallic and multi-metallic catalysts have been explored. Zhang and Wöllner 12 found that PtNi/C nanoparticles significantly reduced OER and ORR overpotentials compared to monometallic catalysts, suggesting that nanostructured electrocatalysts can enhance energy conversion efficiency. Transition metals such as Ni, Co, and Fe present cost-effective alternatives to noble metal catalysts, but their OER performance remains limited due to low intrinsic activity. Their electrocatalytic properties improve when combined with nonmetals and metalloids. Based on the electronic structure of selenium atoms, electrons can be shared with elements that have higher electronegativity values to form transition metal-selenide compounds 13 . Cobalt selenides (CoSe 2 ) demonstrate high electrocatalytic activity and chemical stability. Lan et al. 14 reported that CoSe 2 spheres display OER performance comparable to IrO 2 , with an overpotential of 325 mV at 10 mA-cm − 2 . Nickel selenides (NiSe 2 ) also perform well in both acidic and alkaline media but suffer from low conductivity and limited active sites 15 . The combination of nickel and cobalt selenides has been explored to improve both conductivity and catalytic activity 16 . Catalyst supports perform a crucial role in increasing the number of active sites and facilitating charge transfer. Carbon-based materials such as carbon nanotubes, nanofibers, and graphene improve catalyst dispersion and reduce overpotential 17 . These materials enhance electrocatalytic performance due to their high conductivity and porosity 18 . Hydrochar is a promising low-cost catalyst support with tunable porosity and is derived from hydrothermal carbonization of biomass. Unlike biochar, which requires high-temperature pyrolysis, hydrochar contains oxygen functional groups that improve catalyst dispersion 19 . Panganoron et al. 20 found that hydrochar-based MnO 2 electrocatalysts enhanced OER activity, although further optimization is required to match commercial Pt/C performance. To meet future energy demands, global decarbonization efforts led by the shift to renewable energy must be made, and green hydrogen fuel produced by the electrolysis of water is an emerging but viable solution. Cost-effective and efficient electrocatalysts are needed to reduce the high overpotential of the OER. Nickel-cobalt selenides (NiCoSe) have shown promise as alternative electrocatalysts but necessitate carbon support for improved performance. The use of hydrochar itself as carbon support on NiCoSe has not yet been explored in previous studies. To address this challenge, the study introduces a novel approach to enhance nickel-cobalt selenide electrocatalysts by integrating hydrochar as a carbon-based composite support, significantly improving catalyst dispersion, active site exposure, and overall electrocatalytic performance in the OER. This work also investigates the ideal ratio of transition metal-selenide electrocatalysts with hydrochar support in lowering the overpotential of OER and can serve as a reference for future research on transition metal chalcogenide catalysts. This study aims to develop an electrode using NiCoSe on hydrochar as a catalyst for the oxygen evolution reaction. To achieve this, the study focuses on synthesizing NiCoSe on hydrochar support and characterizing both the pristine NiCoSe and its hydrochar-supported counterpart using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Additionally, the electrocatalytic activity of NiCoSe on hydrochar support is evaluated through linear sweep voltammetry (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The study also investigates the main effects influencing the activity of NiCoSe on hydrochar support by varying the composition of nickel and cobalt, as well as the NiCoSe-to-hydrochar ratio. 2. Methodology 2.1. Materials The nickel-cobalt selenide electrocatalyst on hydrochar support was prepared by combining NiCoSe deposits and activated hydrochar. Nickel (II) sulfate hexahydrate (NiSO 4 ⋅6H 2 O, 99% purity) was purchased from Wako Chemicals. Cobalt (II) sulfate heptahydrate (CoSO 4 ⋅7H 2 O, 99% purity) and selenium dioxide (SeO 2 , 98% purity) were obtained from Sigma Aldrich®. Polyvinyl pyrrolidone (PVP, 100% purity) was purchased from Dalkem Corporation, and potassium chloride (KCl, ≥ 99% purity) was sourced from RCI Labscan Limited. The hydrochar samples used were commercial chitin (poly(N-acetyl-1,4-β-D-glucopyranosamine), ≥ 99% purity) from HiMedia crab shells sourced from the Philippine Textile Research Institute of the Department of Science and Technology (Philippines). The material was chemically doped with melamine (C 3 H 6 N 6 , 99.5% purity), provided by the Tianjin Kemiou Chemical Reagent Co., Ltd. Electrocatalyst testing was facilitated using potassium hydroxide (KOH) from Dalkem Corp. Ethanol (C 2 H 5 OH) was used as the liquid medium for blending with the electrocatalyst. 2.2. Three-electrode system The study used the three-electrode electrochemical cell system to facilitate electrodeposition for producing OER electrocatalytic materials. The setup included a reference electrode (RE), a working electrode (WE), and a counter electrode (CE). An Ag/AgCl RE was selected for its availability and performance in an acidic medium. The carbon-supported NiCoSe electrocatalyst served as the WE, where electrochemical processes occurred at different supplied potentials. A thin Pt wire, functioning as the CE, completed the circuit while minimizing interference. The system was connected to a BioLogic SP-50e Potentiostat with EC Lab software used to set the parameters. 2.3. Synthesis of the nickel-cobalt selenide In 150 mL of deionized water, the crystals of SeO 2 , CoSO 4 ⋅7H 2 O, and NiSO 4 ⋅6H 2 O were dissolved and mixed to form a precursor solution. 1.0 M of KCl supporting electrolyte was added to the solution to increase electrolytic conductivity. The solution underwent electrodeposition with the three-electrode system immersed in it; a nickel strip served as the working electrode for electrodeposition to collect the deposits. The potentiostat supplied a constant voltage of -0.9 V in chronoamperometric mode to produce current versus time plots on the software. The deposits adhered to the strip were scraped using hard plastic into a container. The solution was filtered to recover the remaining mixed-in deposits. 2.4. Hydrochar preparation Chitin was processed in a ball mill to achieve smaller and uniform-sized particles. Hydrothermal carbonization (HTC) was performed for 5 h in an autoclave, which was set to 126 ˚C with 50 mL of water per gram of chitin, producing hydrochar. The carbon material was chemically doped with C 3 H 6 N 6 at a melamine-to-hydrochar mass ratio of 1:1. After further doping in the autoclave, the hydrochar was dried in an oven at 60 ˚C. 2.5. Nickel foam deposition A 0.01 g electrocatalyst load was combined with 0.01 g of hydrochar and 5% PVP (by total solid mass) in a beaker. The solids were mixed with C 2 H 5 OH to form a 20% (w/w) solution. This ethanolic slurry was drop-cast onto a 1 cm by 3 cm nickel foam strip and left to air-dry. 2.6. Electrocatalyst activity and stability testing In CV, each test was made to run five (5) full cycles from − 0.8 to 0.8 V at a constant scan rate of 50 mV-s − 1 . This scan rate was chosen to ensure that readings are not taken at a rate that is too fast, such that it readily exceeds 10 mA-cm − 2 during the anodic cycle without compromising the time required for each experiment. The wide voltage range ensures that the overpotential and other important regions of the voltammogram can be easily identified. The current density of 10 mA-cm − 2 is an important benchmark in comparing the electrocatalyst as it corresponds to a 12.3% solar-to-hydrogen efficiency, which is the average efficiency of a commercial photovoltaic cell that uses solar energy for water splitting 21 . LSV has similar parameters to CV, except it only takes a unidirectional, non-cyclic sweep of the anodic segment. Lastly, for EIS, a single sweep with a frequency range of 0.1 Hz to 100 kHz was used at an amplitude of 0.1 mA. The range ensures low and high frequencies are explored throughout the run, and the amplitude is kept low to maintain the linear relationship between voltage and current per polarization type, which occurs at small current values 22 . 2.7. Characterization of the electrocatalyst and hydrochar The electrocatalyst and support samples first underwent testing for their electrocatalyst activity and stability using the workstation. The sample identified through the identification of main effects was characterized using SEM for morphology with EDS for the elemental distribution, XRD for the crystal structure, and FTIR for the functional groups of the support. A JSM IT500HR/LA Schottky tip Field Emission Scanning Electron Microscope carried out SEM and EDS, and a Shimadzu XRD-7000 MAXima.X diffractometer was used for XRD. The FTIR instrument used was a Shimadzu IRSpirit QATR-S spectrometer. 3. Results and discussion 3.1. Characterization of the Electrocatalyst 3.1.1. FTIR Analysis The identity of chitin used in the study was verified by analyzing the key bands associated with previous studies of chitin to verify unique groups found in its structure (Fig. 1 ). N-linked acetyl groups found in the polysaccharide can be observed through the 1,550-1,650 cm − 1 window containing the N-H and C = O bonds that make up the NHCOCH 3 group in the polysaccharide. In particular, the peak at 1,557 cm − 1 indicates the C-N vibration. The dual peaks from the range between the 1,600 to 1,680 cm − 1 window indicate the amide band of the C = O group and is representative of the α-chitin structure 23 . The stretching between the wavelengths of 2,982 to 3,253 cm − 1 , indicative of a C = O amide group, is also comparable to other literature concerning chitin structures 24 . The hydrothermally carbonized chitin was observed to have undergone substantial degradation and reduction of volatile functional groups in the material structure. The smaller and broader peaks between 1,000–1,700 cm − 1 are indicative of a reduction in the more volatile oxygen groups as the reaction progressed. In particular, the decreased peaks in 1,654 cm − 1 , 1,307 cm − 1 , and 1,068 cm − 1 , respectively, represent the loss of the different C-O and C \(\:=\) O bonds associated with the spectrum. This may have induced greater porosity and allowed for greater electrocatalytic activity for OER 25 . The effect of nitrogen doping using melamine was then analyzed with similar smaller peaks found between 1,000–1,700 cm − 1 as the hydrochar sample further underwent hydrocarbon degradation due to the HTC performed during the doping process. Minor N-H stretching was indicated by a minor peak at 3,468 cm − 1 , while the new peak at 811 cm − 1 could indicate a change in the internal structure of the system affecting the C-H bending of the hydrochar. 3.1.2. SEM-EDS Analysis The changes in the morphological structure of the hydrochar were observed using SEM. A more fibrous and layered network of particles was observed in the hydrochar owing to the various reactions during the HTC process, such as the dehydration and decarboxylation of the chitin structure. However, a lamellar structure was still observed, with most of the fragmentation concentrated on the surface. The surface mapping of the hydrochar found high concentrations of carbon and oxygen with the presence of silicon, aluminum, and iron. The deposition of melamine led to the presence of large melamine particles on the surface of the substrate, with nitrogen making up 62% of the surface mass. The increased roughness of these particles can lead to increased complexity of the subsurface and the increased amount of surface for electrocatalytic activity. Considering the minimal effect of the nitrogen doping process on the internal bonds of the hydrochar substrate, its effect on catalytic activity may be primarily due to its effect on the surface roughness of the hydrochar. The NiCoSe and hydrochar structure exhibited a high level of porosity with the presence of similarly sized spherical particles primarily composed of nickel, cobalt, and selenide particles mixed with the carbon and oxygen components of the hydrochar substrate. The NiCoSe particles were mapped and found to be generally well distributed (Fig. 2 ). There is sufficient surface roughness and a large amount of surface area for electrocatalytic activity. As seen from the SEM on the nickel foam deposited substrates, the addition of the various precursors led to changes in the microstructure, affecting the capability of the substrate to host electrocatalytic active sites. Figure 2 (a) showcased a relatively smooth surface of the pure nickel foam, making it unideal for electrocatalytic activity. The addition of NiCoSe led to greater porosity on the surface but with minimal surface roughness due to the size of the particles. Meanwhile, Fig. 2 (b) indicated a large amount of surface roughness with different-sized spheroidal particles throughout the surface. This transitioned into a more fragmented and striated microstructure in Fig. 2 (c) as further HTC during the doping process led to further degradation of the functional groups and allowed for the formation of a more simple and porous structure. Figure 2 (d) shows that the combination of the hydrochar and NiCoSe upon a nickel surface led to a rough microstructure made up of similarly sized spherical particles. The agglomeration and spherical shape of the structure may be due to the effect of the PVP, which affected the crystallization behavior of the electrocatalyst as its components were agitated and combined 26 . 3.1.3. EDS and XRD Analysis There is a notable amount in mass percentages of Ni (9.98%), Co (15.11%), and Se (52.99%) within the electrocatalyst alongside trace amounts of other elements. The carbon content was derived from the hydrochar support mixed with the electrocatalyst. This corresponds to an atomic ratio of 1:1.5:4 for Ni:Co:Se. In comparison to the theoretical values with a ratio of 1.5:1:5, there was some differentiation between the concentrations of nickel and cobalt in the system. Variations from the observed value may be due to minimal measuring errors caused by the sensitive nature of the measuring equipment alongside the imperfect distribution of Ni, Co, and Se in the electrocatalyst. However, it should be noted that the sample overall may be closer to Ni 0.6 Co 0.4 Se 2 , which is just a localized value. Figure 3 shows the EDS data for the Ni 0.6 Co 0.4 Se 2 point sample. The identity of the Ni 0.6 Co 0.4 Se 2 sample was confirmed using XRD diffractograms (Fig. 4 ) by comparing its corresponding peaks to existing literature. Characteristic peaks at 35 °, 45 °, and 51 ° were like XRD diffraction data in the study of Xie et al. 27 . This confirms the presence of patterns that had previously been identified as NiSe 2 (JCPDS no. 01-088-1711) and CoSe 2 (JCPDS no. 01-089-2002). A high peak at 41 ° can be attributed to the presence of NiO formed in the process of creating the electrocatalyst (JCPDS no. 073-1523) 28 . In comparison to literature concerning other NiCoSe combinations, minimal differences were found, except for a shift to larger angles in the cases of higher cobalt content. The presence of the glass substrate used in the experiment may have led to an observable peak at 28 ° but otherwise caused minimal noise in the data 29 . This further affirms the EDS data obtained, which confirms the identity of the electrocatalyst. 3.2. Overpotential, Tafel Slope, and Stability of the Electrocatalyst 3.2.1. Cyclic Voltammetry and Linear Sweep Voltammetry The optimal parameters identified through JMP are Ni 0.6 Co 0.4 Se 2 with a 1:1 hydrochar-to-electrocatalyst ratio and 0.01 g loading (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01). This sample (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) was able to deliver a 10 mA-cm − 2 current density at an average overpotential of 295.85 mV for three trials. The current density of 10 mA-cm − 2 is considered the accepted benchmark for comparing the performances of electrocatalysts at different media with varying pH conditions, corresponding to the 12.3% solar-to-hydrogen efficiency 21,30 . This presents a 34.42% difference between the (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) sample and nickel foam alone as the working electrode, which was found to have an overpotential of 418.86 mV. The high presence of Se in Ni 0.6 Co 0.4 Se 2 is associated with the electrocatalytic activity of the desired sample when compared to other Ni x Co y Se z compositions in this study. The improvement associated with the increased presence of selenides in the compound is likely due to the ability of transition metal selenides to undergo surface reconstruction 31 . Additionally, the exposure of active sites in the compound is affected by the amounts of Se present as it provides better structural flexibility for the electrocatalyst. The synergistic effect of Co and Ni further increased the electrical conductivity and helped as well to decrease the electronegativity of chalcogenides, increasing the catalytic activity of the electrocatalyst. The importance of selenides being less electronegative allows for faster diffusion of OH − ions in comparison to oxides and sulfides 32 . To observe the effect of hydrochar on the synthesized electrocatalyst (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01), the electrocatalytic activity of Ni 0.6 Co 0.4 Se 2 on a nickel foam (NF) substrate at a 0.01 g loading only was analyzed and compared with the activity of (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) under the same conditions. The difference between the CV results of Ni 0.6 Co 0.4 Se 2 + NF versus Ni 0.6 Co 0.4 Se 2 + HC + NF is observed in Fig. 6 . The plot shows minimal change in the overpotential between the samples with and without hydrochar. However, the overpotential recorded for the Ni 0.6 Co 0.4 Se 2 + NF sample is higher at 315.90 mV. This shows that the Ni 0.6 Co 0.4 Se 2 + HC + NF sample has a lower value by a margin of 6.55% difference. It is also noted that the overpotential associated with a sample of the nickel foam with hydrochar (502.25 mV) is higher than that of the nickel foam substrate only (418.86 mV) despite the support being a part of the sample with the lowest overpotential. One factor is that carbon catalyst supports are primarily added to disperse the actual catalytic material and improve its mass transfer properties 20 . Although some carbon supports are inherently conductive, like graphene, such an assumption is not applicable to all carbon supports. The natural structures in biomass offer beneficial characteristics is another factor. Gao et al. 33 state biomasses form networks that create additional active sites. These structures can contribute to improvements in overpotential without necessarily relying on conductive properties. Since no electrocatalyst is present in the HC + NF and NF samples, the NF effectively acts as both the electrode and electrocatalyst. The increase in overpotential can be attributed to a reduction in the exposed area of NF due to hydrochar blockage. LSV was performed on a sample of (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) to determine its Tafel slope using the Tafel equation described in Eq. ( 1 ), where η represents the overpotential and log j corresponds to the logarithm of the current density at the given overpotential. $$\:\eta\:=a+b\:\text{l}\text{o}\text{g}\left(j\right)$$ 1 In Fig. 7 , the linear sweep voltammograms of (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) are compared to those of the electrocatalyst without HC, the combination of NF and HC, and pure NF only. The Tafel slope is applicable in the Faradaic region of the voltammograms, where the electrochemical reaction occurs in the system 34 . The Tafel slope of (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) was found to be 72.15 mV-dec − 1 . This result further shows the improved performance of introducing the HC-supported Ni 0.6 Co 0.4 Se 2 compared to the other configurations, as a lower Tafel slope is preferred for electrochemical processes. The decrease of Tafel slope values from pure NF to Ni 0.6 Co 0.4 Se 2 with hydrochar on NF indicates an improvement in the OER kinetics of the electrocatalyst 35 . The Tafel slope of the electrocatalyst is also indicative of the exchange current density, which is a descriptor of the catalytic activity 36 . Although the overpotential of the NF + HC sample is notably higher than that of the NF only, it could be observed that the former has a lower Tafel slope, indicating that its contribution to the catalytic activity is not directly a reduction in overpotential, although it may be contributing to a different aspect of catalytic activity beyond the overpotential. The long-term stability and durability of an electrocatalyst is a critical requirement for electrochemical applications. The stability of the (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) sample was determined through a 1,000-cycle test through cyclic voltammetry. The first cycle was not utilized for comparison as the plot still needed to be considered stable and contained an overshoot. The CV plots of (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) for 5 cycles, 500 cycles, and 1,000 cycles are shown in Fig. 8 . There is no substantial deviation in the overpotential values after 1,000 cycles, highlighting its excellent stability with negligible losses. It was found that the difference in overpotential from the first 5 cycles to the last cycle is − 33.62 mV, indicating that the overpotential was further reduced during the stability test. This can be observed in the horizontal shifting of the voltammogram as more cycles are performed and may indicate the exposure of more active sites. A substantial increase in the Ni hump was observed as the number of cycles increased throughout the test, which is distinguished as the ‘bump’ before the Faradaic or linear region begins. This implies that more Ni areas were exposed in the stability test, leading to more intense peaks/humps for Ni oxidation. The prolonged oxidation of Ni present in the substrate or in the electrocatalyst itself causes Ni-based electrocatalysts to have decreased electrocatalytic activity over time. Further examination is required to determine at which point the oxidation of Ni causes a decrease in the electrocatalytic activity 37 . 3.2.2. Electrochemical Impedance Spectroscopy The resistive characteristics of the electrocatalyst are mainly attributed to the interaction of the material surface with the electrolyte, and EIS was used to determine them. The electrochemical impedance was identified using a Nyquist plot with respect to the real resistance. A Voigt circuit was used to evaluate the system and form the Nyquist plot. This circuit was chosen because it can distinguish the semicircles of the low-frequency and high-frequency regions. The identification of capacitive and resistive properties of the materials follows the Voigt circuit analysis. At low frequencies, capacitive behavior dominates due to diffusion processes 38 . In contrast, diffusion effects are minimized as reactants travel shorter distances at high frequencies 38 . The Nyquist plot of the (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) sample compared to nickel foam substrate itself is shown in Fig. 9 . The inclusion of the (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01) electrocatalyst resulted in a substantially smaller high-frequency semicircle than that of the nickel foam substrate only. This is because the radii of the electrocatalyst and the nickel foam substrate only are 15.5 Ω and 53.12 Ω, respectively. The diminishing size of the radius is indicative of a lower charge transfer resistance being present between the electrode/electrolyte interface. According to Ahmadian et al. 39 , lower resistance is also indicative of higher catalytic property. This means that the presence of the catalytic component in the Ni foam is an improvement over the substrate only. The Ohmic drop is associated with the current flow in the electrolyte and is determined through EIS. The Ohmic drop and charge transfer resistance are associated with intrinsic resistances associated with the material. Although the latter is generally expressed as a pseudo-overpotential, it tends to slightly increase the overpotential associated with a current observed on cyclic voltammograms 40 . It was found that the Ohmic drops are 0.7516 Ω and 1.29 Ω for the synthesized electrocatalyst and the nickel foam, respectively. A lower Ohmic drop is preferred as it indicates better conductivity between the electrode and the electrolytic solution 41 . The Ohmic drop of the electrocatalyst is therefore preferable and indicates an improvement in the facilitation of the OER. 3.3. Comparison of Results In comparison to other studies, Table 2 and Fig. 10 show the summary of the overpotential and Tafel slope values of different nickel-cobalt selenide electrocatalysts with different materials and substrates used. Table 2 Comparison of overpotential and Tafel slope values of different NiCoSe electrocatalysts No. Catalyst Substrate Overpotential (mV) at 10 mA-cm -2 Tafel Slope mV-dec -1 Reference 1 Ni 0.6 Co 0.4 Se 2 Nickel Foam (NF) + Hydrochar 295.85 72.15 This work 2 NiCoSe 2 nano-brush NF 274 61.2 Xia et al. 42 3 NiCo 2 Se 4 nanowire Glassy Carbon Electrode (GCE) 270 63 Jeghan & Gibaek 43 4 NiCo 2 Se 4 nanoarray Carbon Cloth (CC) 340 89 Yu et al. 44 5 NiCo 2 Se 4 nanosheet NF 183 88 Akbar et al. 45 6 Ni 0.25 Co 0.75 Se NF 269 74 Liu et al. 46 7 NiCoSe Sulfoselenide/Black Phosphorus 285 116 Liang et al. 47 8 NiSe 2 Nanocrystals - 250 38 Kwak et al. 48 9 IrO 2 ( for comparison ) - 310 69 Lan et al. 14 Nickel-cobalt selenide electrocatalysts using NF as the substrate have superior OER performance, compared to the catalysts that use other materials as substrate, in terms of overpotential and Tafel slope values. Moreover, the performance of the synthesized electrocatalyst in this work has obtained close overpotential and Tafel slope values to a noble metal-based electrocatalyst (IrO 2 ) based on Lan et al. 14 . Comparing the synthesized catalyst with the commercial noble metal-based catalyst (IrO 2 ), there was an improvement in the electrocatalytic performance represented by a decrease in the overpotential value. The synthesized catalyst exhibited a 4.56% lower overpotential with a slightly higher Tafel slope (4.56% higher) over a commercial IrO 2 catalyst. Furthermore, these values are within 15% of the average between a sample of performance data from similar NiCoSe-based catalysts, indicating that the synthesized catalyst has comparable performance with the IrO 2 catalyst. However, the synthesis of Ni 0.6 Co 0.4 Se 2 + HC + NF in this study has a higher Tafel slope value compared to other electrocatalysts. This may be attributed to the composition and distribution of Ni and Co relative to the Se in the compounds. Based on Table 2 , the OER performance of the synthesized catalyst is most comparable to the results of Liu et al. 46 . Although the overpotential is higher by 9.98%, the obtained value of the Tafel slope is lower by 2.5%, which is attributed to the presence of HC in the electrocatalyst. The hydrochar in the synthesized catalyst may have contributed to having improved conductivity and higher surface area for its OER performance. 4. Conclusions The synthesized Ni 0.6 Co 0.4 Se 2 supported on hydrochar produces enhanced electrocatalytic activity for the oxygen evolution reaction. The electrocatalyst composition identified from analyzing the main effects, Ni 0.6 Co 0.4 Se 2 with a 1:1 doped hydrochar ratio (Ni 0.6 Co 0.4 Se 2 , 1:1, 0.01), exhibited a low overpotential and high current density, indicative of improved performance over other tested compositions. The 1:1 loading ratio of hydrochar to NiCoSe was found to be desirable, balancing the availability of active sites with the structural support provided by the hydrochar. SEM results confirm the well-dispersed nickel, cobalt, and selenium distribution on the hydrochar support. Furthermore, the EDS confirmed the presence of nickel, cobalt, and selenium elements in the desired ratios, indicating the successful synthesis of the NiCoSe electrocatalyst on the hydrochar support. The use of hydrochar provided additional surface support that expanded the number of active sites, while its combination with the PVP led to the spherical agglomeration of the subsurface that increased the inherent porosity of the electrocatalyst. The effect of NiCo:Se ratio, loading, and hydrochar-to-electrocatalyst ratio can be further explored and optimized in future works. As this study only identified the parameters that resulted in an overall lower overpotential, a succeeding study may explore optimizing the interactions between these parameters. The activity and stability of the electrocatalyst may also be explored in acidic media, while stability may also be further studied through an extended-period electrolysis test. The use of the synthesized electrocatalyst may also be explored in the hydrogen evolution reaction, in conjunction with the OER or on its own. Declarations Availability of data and materials The data collected and analyzed for the present study are available from the corresponding author upon reasonable request. Acknowledgement The authors acknowledge Dr. Jose Paolo Bantang of the Department of Chemistry for providing the chitin sample necessary for the preparation of hydrochar, Dr. Joan Candice Ondevilla of the Department of Chemistry for their assistance in the FTIR characterization. Funding Declaration This research work is funded by the De La Salle University Science Foundation, Research Grants and Management Office (RGMO) – University Research Coordination Office (URCO). CRediT authorship contribution statement Joaquin Nathaniel A. Perez : Writing - Original Draft, Writing - Review & Editing, Investigation, Visualization. Chris Ivan B. Sungcang: Writing - Original Draft, Writing - Review & Editing, Investigation, Visualization. Patricia Isabel R. Soriano : Writing - Original Draft, Data Curation, Investigation, Visualization. Gio Jerson C. Almonte : Writing - Original Draft, Investigation, Visualization. Angelo Earvin Sy Choi : Supervision, Project Administration, Resources. Joseph R. Ortenero : Funding acquisition, Supervision, Project Administration, Conceptualization, Methodology, Resources. 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B., Chavan, P. P. & Sathe, B. R. Enhanced electrocatalytic activity towards urea oxidation on Ni nanoparticle decorated graphene oxide nanocomposite. Electrochim. Acta 349 , 136386 (2020). Magar, H. S., Hassan, R. Y. A. & Mulchandani, A. Electrochemical Impedance Spectroscopy (EIS): Principles, Construction, and Biosensing Applications. Sensors (Basel). 21 , (2021). Ahmadian, F., Salarvand, V., Saghafi, M., Noghani, M. T. & Yousefifar, A. Production and characterization of high-performance cobalt–nickel selenide catalyst with excellent activity in HER. J. Mater. Res. Technol. 15 , 3942–3950 (2021). Trasatti, S. Hydrogen Evolution. 41–48 at https://doi.org/https://doi.org/10.1016/B978-044452745-5.00022-8 (2009). Anantharaj, S. & Noda, S. iR drop correction in electrocatalysis: everything one needs to know! J. Mater. Chem. A 10 , 9348–9354 (2022). Xia, C., Liang, H., Zhu, J., Schwingenschlögl, U. & Alshareef, H. N. 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Interface and M3+/M2+ Valence Dual-Engineering on Nickel Cobalt Sulfoselenide/Black Phosphorus Heterostructure for Efficient Water Splitting Electrocatalysis. ENERGY Environ. Mater. 6 , e12332 (2023). Kwak, I. H. et al. CoSe2 and NiSe2 Nanocrystals as Superior Bifunctional Catalysts for Electrochemical and Photoelectrochemical Water Splitting. ACS Appl. Mater. Interfaces 8 , 5327–5334 (2016). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 06 Oct, 2025 Reviews received at journal 06 Oct, 2025 Reviewers agreed at journal 29 Sep, 2025 Reviews received at journal 26 Sep, 2025 Reviews received at journal 12 Sep, 2025 Reviewers agreed at journal 12 Sep, 2025 Reviewers agreed at journal 12 Sep, 2025 Reviewers invited by journal 05 Sep, 2025 Editor assigned by journal 04 Sep, 2025 Editor invited by journal 04 Sep, 2025 Submission checks completed at journal 02 Sep, 2025 First submitted to journal 02 Sep, 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-7450657","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":510679422,"identity":"ab04d28c-202d-42c0-a168-9b434785e69b","order_by":0,"name":"Joaquin Nathaniel A. Perez","email":"","orcid":"","institution":"De La Salle University","correspondingAuthor":false,"prefix":"","firstName":"Joaquin","middleName":"Nathaniel A.","lastName":"Perez","suffix":""},{"id":510679423,"identity":"1e9c5bff-f615-4589-ae47-b77e65aeaecf","order_by":1,"name":"Chris Ivan B. Sungcang","email":"","orcid":"","institution":"De La Salle University","correspondingAuthor":false,"prefix":"","firstName":"Chris","middleName":"Ivan B.","lastName":"Sungcang","suffix":""},{"id":510679424,"identity":"7344b818-d472-4360-9569-7e143d6c0aca","order_by":2,"name":"Patricia Isabel R. Soriano","email":"","orcid":"","institution":"De La Salle University","correspondingAuthor":false,"prefix":"","firstName":"Patricia","middleName":"Isabel R.","lastName":"Soriano","suffix":""},{"id":510679425,"identity":"55b565d3-83c3-4281-9e2a-59719587d654","order_by":3,"name":"Gio Jerson C. 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Ortenero","email":"data:image/png;base64,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","orcid":"","institution":"De La Salle University","correspondingAuthor":true,"prefix":"","firstName":"Joseph","middleName":"R.","lastName":"Ortenero","suffix":""}],"badges":[],"createdAt":"2025-08-25 07:08:58","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7450657/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7450657/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":91089896,"identity":"af3fbb37-e565-450d-a529-f884c74b44b1","added_by":"auto","created_at":"2025-09-11 12:57:37","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":111907,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of hydrochar at various treatment stages\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/331d4adfc68b8213fc266625.png"},{"id":91088756,"identity":"4e4c80b3-8502-4bbe-8f47-aa072e0d2ac4","added_by":"auto","created_at":"2025-09-11 12:49:37","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":710062,"visible":true,"origin":"","legend":"\u003cp\u003eSEM Pictures of (a) nickel foam (NF); (b) undoped hydrochar (HC); (c) doped HC with NF. Magnification of 30,000x with 5.0 kV accelerating voltage; (d) Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e with HC deposited on NF in 1:1 loading. Magnification of 30,000x with 10.0 kV accelerating voltage.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/c62cb3d60127ccd3f48eeb3b.png"},{"id":91090184,"identity":"eec3dc8b-068f-417d-be37-f34df4b2e802","added_by":"auto","created_at":"2025-09-11 13:05:37","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":83455,"visible":true,"origin":"","legend":"\u003cp\u003eEDS data for Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/c0b3452d379d67ff551ab49c.png"},{"id":91089900,"identity":"5f85a0a7-12d1-49b1-b489-1c2c98afbb28","added_by":"auto","created_at":"2025-09-11 12:57:37","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":86983,"visible":true,"origin":"","legend":"\u003cp\u003eXRD data for Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/42e46833757cffc6b660caad.png"},{"id":91088762,"identity":"dc521b72-2ccb-4fbf-9a22-2b36090151bd","added_by":"auto","created_at":"2025-09-11 12:49:37","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":119485,"visible":true,"origin":"","legend":"\u003cp\u003eCyclic voltammogram\u003cstrong\u003e \u003c/strong\u003ecomparison of Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e with HC and NF combinations. Scan rate of 50 mV/s in 1 M KOH.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/8a77895b9574bc5f5eb14199.png"},{"id":91090185,"identity":"e3abb7ba-72d0-4c39-ae44-feee789bd83a","added_by":"auto","created_at":"2025-09-11 13:05:37","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":120877,"visible":true,"origin":"","legend":"\u003cp\u003eTafel slope plot comparison of Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e with HC and NF combinations. Scan rate of 50 mV/s in 1 M KOH.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/5506116a1c67b8786a489f13.png"},{"id":91089903,"identity":"2ce4f5d7-6de3-47b2-bf8d-527ff9a98ef7","added_by":"auto","created_at":"2025-09-11 12:57:37","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":104761,"visible":true,"origin":"","legend":"\u003cp\u003eCyclic voltammetry plot of (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) for 5, 500, and 1,000 cycles. Scan rate of 50 mV/s in 1 M KOH.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/f9b7f3e3bd415cea6fada291.png"},{"id":91089904,"identity":"5329f06a-9157-4bb6-9256-3a1323500fb6","added_by":"auto","created_at":"2025-09-11 12:57:37","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":80367,"visible":true,"origin":"","legend":"\u003cp\u003eNyquist impedance plots comparing the performance of the (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) electrocatalyst (red) with that of the nickel foam substrate only (black). (a) Full plot; (b) Plot at high frequency range. Frequency range of 0.1 Hz to 100 kHz at an amplitude of 0.1 mA in 1 M KOH.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/897768d62a3ab20de8b4d3f5.png"},{"id":91088772,"identity":"e96924a8-1ebe-4f35-9da9-4d64f625f278","added_by":"auto","created_at":"2025-09-11 12:49:37","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":105601,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical comparison of catalysts presented in Table 2. (a) Tafel slope; (b) Overpotential; (c) Tafel slope-overpotential scatterplot\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/12d02e43196117ed54147a1f.png"},{"id":91091247,"identity":"3c783af8-a1ac-4d8e-b656-8e93be5fd8cf","added_by":"auto","created_at":"2025-09-11 13:13:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2557152,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7450657/v1/875f6c87-2e35-4f65-ab61-3a605925cfbb.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Hydrochar-Supported Nickel-Cobalt Selenide Electrocatalyst for Enhanced Oxygen Evolution Reaction Performance","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIn 2023, approximately 30% of the total energy supply was derived from renewable sources. The growth of solar and wind energy is projected to bring up the total renewable energy share to 46% \u003csup\u003e1\u003c/sup\u003e. However, the variability and lack of storage capacity for solar and wind-based energy hinder its ability to decarbonize the transport industry and necessitate the development of storage technology that is versatile for other important industries \u003csup\u003e2\u003c/sup\u003e. Efforts to address these issues are emphasized by growing trends to explore the use of hydrogen fuel as a clean and reliable energy carrier for future energy demand \u003csup\u003e3\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eGreen hydrogen may be produced through the electrolysis of water, but a common problem with these systems is the slow kinetics of the oxygen evolution reaction (OER). A high overpotential causes the reaction to proceed non-spontaneously. Electrocatalysts can be used to remedy the high OER overpotential, but common noble metal catalysts are expensive and not readily available \u003csup\u003e4\u003c/sup\u003e. This has paved the way for the use of more cost-effective transition metal chalcogenides (TMCs). Some examples include nickel-cobalt selenide catalysts, which exhibit strong electrocatalytic abilities like noble metal catalysts. However, its relatively low electric conductivity and active sites require the use of support materials to improve its performance \u003csup\u003e5\u003c/sup\u003e. The emergence of carbon-based supports presents a renewable, ubiquitous, and effective method to support TMCs. One such support is hydrochar, which may be derived from a wide range of biomass sources to create a low-cost carbon-based material that can be used to improve the dispersion of TMCs and their overall electrocatalytic activity.\u003c/p\u003e\u003cp\u003eThe sluggish kinetics of the OER result in high overpotential, requiring the use of catalysts to improve reaction rates. Pt, Ni, and IrO\u003csub\u003ex\u003c/sub\u003e catalysts have been examined previously. Pt-based catalysts are greatly effective for the oxygen reduction reaction (ORR) but degrade quickly in OER, limiting their long-term stability \u003csup\u003e6,7\u003c/sup\u003e. Nickel oxides are inherently less active but exhibit improved performance when doped with Fe. They create NiFeO\u003csub\u003ex\u003c/sub\u003e compounds with high turnover frequency \u003csup\u003e8,9\u003c/sup\u003e. However, the debate over whether Ni or Fe functions as the primary active site remains. IrO\u003csub\u003ex\u003c/sub\u003e-based compounds demonstrate excellent OER activity and stability, but their high cost and scarcity limit large-scale application \u003csup\u003e10,11\u003c/sup\u003e. To address these limitations, bimetallic and multi-metallic catalysts have been explored. Zhang and W\u0026ouml;llner \u003csup\u003e12\u003c/sup\u003e found that PtNi/C nanoparticles significantly reduced OER and ORR overpotentials compared to monometallic catalysts, suggesting that nanostructured electrocatalysts can enhance energy conversion efficiency.\u003c/p\u003e\u003cp\u003eTransition metals such as Ni, Co, and Fe present cost-effective alternatives to noble metal catalysts, but their OER performance remains limited due to low intrinsic activity. Their electrocatalytic properties improve when combined with nonmetals and metalloids. Based on the electronic structure of selenium atoms, electrons can be shared with elements that have higher electronegativity values to form transition metal-selenide compounds \u003csup\u003e13\u003c/sup\u003e. Cobalt selenides (CoSe\u003csub\u003e2\u003c/sub\u003e) demonstrate high electrocatalytic activity and chemical stability. Lan et al. \u003csup\u003e14\u003c/sup\u003e reported that CoSe\u003csub\u003e2\u003c/sub\u003e spheres display OER performance comparable to IrO\u003csub\u003e2\u003c/sub\u003e, with an overpotential of 325 mV at 10 mA-cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. Nickel selenides (NiSe\u003csub\u003e2\u003c/sub\u003e) also perform well in both acidic and alkaline media but suffer from low conductivity and limited active sites \u003csup\u003e15\u003c/sup\u003e. The combination of nickel and cobalt selenides has been explored to improve both conductivity and catalytic activity \u003csup\u003e16\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eCatalyst supports perform a crucial role in increasing the number of active sites and facilitating charge transfer. Carbon-based materials such as carbon nanotubes, nanofibers, and graphene improve catalyst dispersion and reduce overpotential \u003csup\u003e17\u003c/sup\u003e. These materials enhance electrocatalytic performance due to their high conductivity and porosity \u003csup\u003e18\u003c/sup\u003e. Hydrochar is a promising low-cost catalyst support with tunable porosity and is derived from hydrothermal carbonization of biomass. Unlike biochar, which requires high-temperature pyrolysis, hydrochar contains oxygen functional groups that improve catalyst dispersion \u003csup\u003e19\u003c/sup\u003e. Panganoron et al. \u003csup\u003e20\u003c/sup\u003e found that hydrochar-based MnO\u003csub\u003e2\u003c/sub\u003e electrocatalysts enhanced OER activity, although further optimization is required to match commercial Pt/C performance.\u003c/p\u003e\u003cp\u003eTo meet future energy demands, global decarbonization efforts led by the shift to renewable energy must be made, and green hydrogen fuel produced by the electrolysis of water is an emerging but viable solution. Cost-effective and efficient electrocatalysts are needed to reduce the high overpotential of the OER. Nickel-cobalt selenides (NiCoSe) have shown promise as alternative electrocatalysts but necessitate carbon support for improved performance. The use of hydrochar itself as carbon support on NiCoSe has not yet been explored in previous studies. To address this challenge, the study introduces a novel approach to enhance nickel-cobalt selenide electrocatalysts by integrating hydrochar as a carbon-based composite support, significantly improving catalyst dispersion, active site exposure, and overall electrocatalytic performance in the OER. This work also investigates the ideal ratio of transition metal-selenide electrocatalysts with hydrochar support in lowering the overpotential of OER and can serve as a reference for future research on transition metal chalcogenide catalysts.\u003c/p\u003e\u003cp\u003eThis study aims to develop an electrode using NiCoSe on hydrochar as a catalyst for the oxygen evolution reaction. To achieve this, the study focuses on synthesizing NiCoSe on hydrochar support and characterizing both the pristine NiCoSe and its hydrochar-supported counterpart using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Additionally, the electrocatalytic activity of NiCoSe on hydrochar support is evaluated through linear sweep voltammetry (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The study also investigates the main effects influencing the activity of NiCoSe on hydrochar support by varying the composition of nickel and cobalt, as well as the NiCoSe-to-hydrochar ratio.\u003c/p\u003e"},{"header":"2. Methodology","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Materials\u003c/h2\u003e\u003cp\u003eThe nickel-cobalt selenide electrocatalyst on hydrochar support was prepared by combining NiCoSe deposits and activated hydrochar. Nickel (II) sulfate hexahydrate (NiSO\u003csub\u003e4\u003c/sub\u003e\u0026sdot;6H\u003csub\u003e2\u003c/sub\u003eO, 99% purity) was purchased from Wako Chemicals. Cobalt (II) sulfate heptahydrate (CoSO\u003csub\u003e4\u003c/sub\u003e\u0026sdot;7H\u003csub\u003e2\u003c/sub\u003eO, 99% purity) and selenium dioxide (SeO\u003csub\u003e2\u003c/sub\u003e, 98% purity) were obtained from Sigma Aldrich\u0026reg;. Polyvinyl pyrrolidone (PVP, 100% purity) was purchased from Dalkem Corporation, and potassium chloride (KCl, \u0026ge; 99% purity) was sourced from RCI Labscan Limited.\u003c/p\u003e\u003cp\u003eThe hydrochar samples used were commercial chitin (poly(N-acetyl-1,4-β-D-glucopyranosamine), \u0026ge; 99% purity) from HiMedia crab shells sourced from the Philippine Textile Research Institute of the Department of Science and Technology (Philippines). The material was chemically doped with melamine (C\u003csub\u003e3\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eN\u003csub\u003e6\u003c/sub\u003e, 99.5% purity), provided by the Tianjin Kemiou Chemical Reagent Co., Ltd. Electrocatalyst testing was facilitated using potassium hydroxide (KOH) from Dalkem Corp. Ethanol (C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eOH) was used as the liquid medium for blending with the electrocatalyst.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Three-electrode system\u003c/h2\u003e\u003cp\u003eThe study used the three-electrode electrochemical cell system to facilitate electrodeposition for producing OER electrocatalytic materials. The setup included a reference electrode (RE), a working electrode (WE), and a counter electrode (CE). An Ag/AgCl RE was selected for its availability and performance in an acidic medium. The carbon-supported NiCoSe electrocatalyst served as the WE, where electrochemical processes occurred at different supplied potentials. A thin Pt wire, functioning as the CE, completed the circuit while minimizing interference. The system was connected to a BioLogic SP-50e Potentiostat with EC Lab software used to set the parameters.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Synthesis of the nickel-cobalt selenide\u003c/h2\u003e\u003cp\u003eIn 150 mL of deionized water, the crystals of SeO\u003csub\u003e2\u003c/sub\u003e, CoSO\u003csub\u003e4\u003c/sub\u003e\u0026sdot;7H\u003csub\u003e2\u003c/sub\u003eO, and NiSO\u003csub\u003e4\u003c/sub\u003e\u0026sdot;6H\u003csub\u003e2\u003c/sub\u003eO were dissolved and mixed to form a precursor solution. 1.0 M of KCl supporting electrolyte was added to the solution to increase electrolytic conductivity. The solution underwent electrodeposition with the three-electrode system immersed in it; a nickel strip served as the working electrode for electrodeposition to collect the deposits. The potentiostat supplied a constant voltage of -0.9 V in chronoamperometric mode to produce current versus time plots on the software. The deposits adhered to the strip were scraped using hard plastic into a container. The solution was filtered to recover the remaining mixed-in deposits.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Hydrochar preparation\u003c/h2\u003e\u003cp\u003eChitin was processed in a ball mill to achieve smaller and uniform-sized particles. Hydrothermal carbonization (HTC) was performed for 5 h in an autoclave, which was set to 126 ˚C with 50 mL of water per gram of chitin, producing hydrochar. The carbon material was chemically doped with C\u003csub\u003e3\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eN\u003csub\u003e6\u003c/sub\u003e at a melamine-to-hydrochar mass ratio of 1:1. After further doping in the autoclave, the hydrochar was dried in an oven at 60 ˚C.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Nickel foam deposition\u003c/h2\u003e\u003cp\u003eA 0.01 g electrocatalyst load was combined with 0.01 g of hydrochar and 5% PVP (by total solid mass) in a beaker. The solids were mixed with C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eOH to form a 20% (w/w) solution. This ethanolic slurry was drop-cast onto a 1 cm by 3 cm nickel foam strip and left to air-dry.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6. Electrocatalyst activity and stability testing\u003c/h2\u003e\u003cp\u003eIn CV, each test was made to run five (5) full cycles from \u0026minus;\u0026thinsp;0.8 to 0.8 V at a constant scan rate of 50 mV-s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. This scan rate was chosen to ensure that readings are not taken at a rate that is too fast, such that it readily exceeds 10 mA-cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e during the anodic cycle without compromising the time required for each experiment. The wide voltage range ensures that the overpotential and other important regions of the voltammogram can be easily identified. The current density of 10 mA-cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e is an important benchmark in comparing the electrocatalyst as it corresponds to a 12.3% solar-to-hydrogen efficiency, which is the average efficiency of a commercial photovoltaic cell that uses solar energy for water splitting \u003csup\u003e21\u003c/sup\u003e. LSV has similar parameters to CV, except it only takes a unidirectional, non-cyclic sweep of the anodic segment. Lastly, for EIS, a single sweep with a frequency range of 0.1 Hz to 100 kHz was used at an amplitude of 0.1 mA. The range ensures low and high frequencies are explored throughout the run, and the amplitude is kept low to maintain the linear relationship between voltage and current per polarization type, which occurs at small current values \u003csup\u003e22\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.7. Characterization of the electrocatalyst and hydrochar\u003c/h2\u003e\u003cp\u003eThe electrocatalyst and support samples first underwent testing for their electrocatalyst activity and stability using the workstation. The sample identified through the identification of main effects was characterized using SEM for morphology with EDS for the elemental distribution, XRD for the crystal structure, and FTIR for the functional groups of the support.\u003c/p\u003e\u003cp\u003eA JSM IT500HR/LA Schottky tip Field Emission Scanning Electron Microscope carried out SEM and EDS, and a Shimadzu XRD-7000 MAXima.X diffractometer was used for XRD. The FTIR instrument used was a Shimadzu IRSpirit QATR-S spectrometer.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Characterization of the Electrocatalyst\u003c/h2\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e3.1.1. FTIR Analysis\u003c/h2\u003e\u003cp\u003eThe identity of chitin used in the study was verified by analyzing the key bands associated with previous studies of chitin to verify unique groups found in its structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). N-linked acetyl groups found in the polysaccharide can be observed through the 1,550-1,650 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e window containing the N-H and C\u0026thinsp;=\u0026thinsp;O bonds that make up the NHCOCH\u003csub\u003e3\u003c/sub\u003e group in the polysaccharide. In particular, the peak at 1,557 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e indicates the C-N vibration. The dual peaks from the range between the 1,600 to 1,680 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e window indicate the amide band of the C\u0026thinsp;=\u0026thinsp;O group and is representative of the α-chitin structure \u003csup\u003e23\u003c/sup\u003e. The stretching between the wavelengths of 2,982 to 3,253 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, indicative of a C\u0026thinsp;=\u0026thinsp;O amide group, is also comparable to other literature concerning chitin structures \u003csup\u003e24\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe hydrothermally carbonized chitin was observed to have undergone substantial degradation and reduction of volatile functional groups in the material structure. The smaller and broader peaks between 1,000\u0026ndash;1,700 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are indicative of a reduction in the more volatile oxygen groups as the reaction progressed. In particular, the decreased peaks in 1,654 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1,307 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 1,068 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, represent the loss of the different C-O and C\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:=\\)\u003c/span\u003e\u003c/span\u003eO bonds associated with the spectrum. This may have induced greater porosity and allowed for greater electrocatalytic activity for OER \u003csup\u003e25\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe effect of nitrogen doping using melamine was then analyzed with similar smaller peaks found between 1,000\u0026ndash;1,700 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e as the hydrochar sample further underwent hydrocarbon degradation due to the HTC performed during the doping process. Minor N-H stretching was indicated by a minor peak at 3,468 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, while the new peak at 811 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e could indicate a change in the internal structure of the system affecting the C-H bending of the hydrochar.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\u003ch2\u003e3.1.2. SEM-EDS Analysis\u003c/h2\u003e\u003cp\u003eThe changes in the morphological structure of the hydrochar were observed using SEM. A more fibrous and layered network of particles was observed in the hydrochar owing to the various reactions during the HTC process, such as the dehydration and decarboxylation of the chitin structure. However, a lamellar structure was still observed, with most of the fragmentation concentrated on the surface. The surface mapping of the hydrochar found high concentrations of carbon and oxygen with the presence of silicon, aluminum, and iron.\u003c/p\u003e\u003cp\u003eThe deposition of melamine led to the presence of large melamine particles on the surface of the substrate, with nitrogen making up 62% of the surface mass. The increased roughness of these particles can lead to increased complexity of the subsurface and the increased amount of surface for electrocatalytic activity. Considering the minimal effect of the nitrogen doping process on the internal bonds of the hydrochar substrate, its effect on catalytic activity may be primarily due to its effect on the surface roughness of the hydrochar.\u003c/p\u003e\u003cp\u003eThe NiCoSe and hydrochar structure exhibited a high level of porosity with the presence of similarly sized spherical particles primarily composed of nickel, cobalt, and selenide particles mixed with the carbon and oxygen components of the hydrochar substrate. The NiCoSe particles were mapped and found to be generally well distributed (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). There is sufficient surface roughness and a large amount of surface area for electrocatalytic activity.\u003c/p\u003e\u003cp\u003eAs seen from the SEM on the nickel foam deposited substrates, the addition of the various precursors led to changes in the microstructure, affecting the capability of the substrate to host electrocatalytic active sites. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e showcased a relatively smooth surface of the pure nickel foam, making it unideal for electrocatalytic activity. The addition of NiCoSe led to greater porosity on the surface but with minimal surface roughness due to the size of the particles. Meanwhile, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e indicated a large amount of surface roughness with different-sized spheroidal particles throughout the surface. This transitioned into a more fragmented and striated microstructure in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(c)\u003c/b\u003e as further HTC during the doping process led to further degradation of the functional groups and allowed for the formation of a more simple and porous structure. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(d)\u003c/b\u003e shows that the combination of the hydrochar and NiCoSe upon a nickel surface led to a rough microstructure made up of similarly sized spherical particles. The agglomeration and spherical shape of the structure may be due to the effect of the PVP, which affected the crystallization behavior of the electrocatalyst as its components were agitated and combined \u003csup\u003e26\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\u003ch2\u003e3.1.3. EDS and XRD Analysis\u003c/h2\u003e\u003cp\u003eThere is a notable amount in mass percentages of Ni (9.98%), Co (15.11%), and Se (52.99%) within the electrocatalyst alongside trace amounts of other elements. The carbon content was derived from the hydrochar support mixed with the electrocatalyst. This corresponds to an atomic ratio of 1:1.5:4 for Ni:Co:Se. In comparison to the theoretical values with a ratio of 1.5:1:5, there was some differentiation between the concentrations of nickel and cobalt in the system. Variations from the observed value may be due to minimal measuring errors caused by the sensitive nature of the measuring equipment alongside the imperfect distribution of Ni, Co, and Se in the electrocatalyst. However, it should be noted that the sample overall may be closer to Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, which is just a localized value. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the EDS data for the Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e point sample.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe identity of the Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e sample was confirmed using XRD diffractograms (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) by comparing its corresponding peaks to existing literature. Characteristic peaks at 35 \u0026deg;, 45 \u0026deg;, and 51 \u0026deg; were like XRD diffraction data in the study of Xie et al. \u003csup\u003e27\u003c/sup\u003e. This confirms the presence of patterns that had previously been identified as NiSe\u003csub\u003e2\u003c/sub\u003e (JCPDS no. 01-088-1711) and CoSe\u003csub\u003e2\u003c/sub\u003e (JCPDS no. 01-089-2002). A high peak at 41 \u0026deg; can be attributed to the presence of NiO formed in the process of creating the electrocatalyst (JCPDS no. 073-1523) \u003csup\u003e28\u003c/sup\u003e. In comparison to literature concerning other NiCoSe combinations, minimal differences were found, except for a shift to larger angles in the cases of higher cobalt content. The presence of the glass substrate used in the experiment may have led to an observable peak at 28 \u0026deg; but otherwise caused minimal noise in the data \u003csup\u003e29\u003c/sup\u003e. This further affirms the EDS data obtained, which confirms the identity of the electrocatalyst.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Overpotential, Tafel Slope, and Stability of the Electrocatalyst\u003c/h2\u003e\u003cdiv id=\"Sec16\" class=\"Section3\"\u003e\u003ch2\u003e3.2.1. Cyclic Voltammetry and Linear Sweep Voltammetry\u003c/h2\u003e\u003cp\u003eThe optimal parameters identified through JMP are Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e with a 1:1 hydrochar-to-electrocatalyst ratio and 0.01 g loading (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01). This sample (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) was able to deliver a 10 mA-cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e current density at an average overpotential of 295.85 mV for three trials. The current density of 10 mA-cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e is considered the accepted benchmark for comparing the performances of electrocatalysts at different media with varying pH conditions, corresponding to the 12.3% solar-to-hydrogen efficiency \u003csup\u003e21,30\u003c/sup\u003e. This presents a 34.42% difference between the (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) sample and nickel foam alone as the working electrode, which was found to have an overpotential of 418.86 mV.\u003c/p\u003e\u003cp\u003eThe high presence of Se in Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e is associated with the electrocatalytic activity of the desired sample when compared to other Ni\u003csub\u003ex\u003c/sub\u003eCo\u003csub\u003ey\u003c/sub\u003eSe\u003csub\u003ez\u003c/sub\u003e compositions in this study. The improvement associated with the increased presence of selenides in the compound is likely due to the ability of transition metal selenides to undergo surface reconstruction \u003csup\u003e31\u003c/sup\u003e. Additionally, the exposure of active sites in the compound is affected by the amounts of Se present as it provides better structural flexibility for the electrocatalyst. The synergistic effect of Co and Ni further increased the electrical conductivity and helped as well to decrease the electronegativity of chalcogenides, increasing the catalytic activity of the electrocatalyst. The importance of selenides being less electronegative allows for faster diffusion of OH\u003csup\u003e\u0026minus;\u003c/sup\u003e ions in comparison to oxides and sulfides \u003csup\u003e32\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eTo observe the effect of hydrochar on the synthesized electrocatalyst (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01), the electrocatalytic activity of Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e on a nickel foam (NF) substrate at a 0.01 g loading only was analyzed and compared with the activity of (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) under the same conditions. The difference between the CV results of Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e + NF versus Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e + HC\u0026thinsp;+\u0026thinsp;NF is observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The plot shows minimal change in the overpotential between the samples with and without hydrochar. However, the overpotential recorded for the Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e + NF sample is higher at 315.90 mV. This shows that the Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e + HC\u0026thinsp;+\u0026thinsp;NF sample has a lower value by a margin of 6.55% difference.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIt is also noted that the overpotential associated with a sample of the nickel foam with hydrochar (502.25 mV) is higher than that of the nickel foam substrate only (418.86 mV) despite the support being a part of the sample with the lowest overpotential. One factor is that carbon catalyst supports are primarily added to disperse the actual catalytic material and improve its mass transfer properties \u003csup\u003e20\u003c/sup\u003e. Although some carbon supports are inherently conductive, like graphene, such an assumption is not applicable to all carbon supports. The natural structures in biomass offer beneficial characteristics is another factor. Gao et al. \u003csup\u003e33\u003c/sup\u003e state biomasses form networks that create additional active sites. These structures can contribute to improvements in overpotential without necessarily relying on conductive properties. Since no electrocatalyst is present in the HC\u0026thinsp;+\u0026thinsp;NF and NF samples, the NF effectively acts as both the electrode and electrocatalyst. The increase in overpotential can be attributed to a reduction in the exposed area of NF due to hydrochar blockage.\u003c/p\u003e\u003cp\u003eLSV was performed on a sample of (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) to determine its Tafel slope using the Tafel equation described in Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), where η represents the overpotential and \u003cem\u003elog j\u003c/em\u003e corresponds to the logarithm of the current density at the given overpotential.\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:\\eta\\:=a+b\\:\\text{l}\\text{o}\\text{g}\\left(j\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e, the linear sweep voltammograms of (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) are compared to those of the electrocatalyst without HC, the combination of NF and HC, and pure NF only. The Tafel slope is applicable in the Faradaic region of the voltammograms, where the electrochemical reaction occurs in the system \u003csup\u003e34\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe Tafel slope of (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) was found to be 72.15 mV-dec\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. This result further shows the improved performance of introducing the HC-supported Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e compared to the other configurations, as a lower Tafel slope is preferred for electrochemical processes. The decrease of Tafel slope values from pure NF to Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e with hydrochar on NF indicates an improvement in the OER kinetics of the electrocatalyst \u003csup\u003e35\u003c/sup\u003e. The Tafel slope of the electrocatalyst is also indicative of the exchange current density, which is a descriptor of the catalytic activity \u003csup\u003e36\u003c/sup\u003e. Although the overpotential of the NF\u0026thinsp;+\u0026thinsp;HC sample is notably higher than that of the NF only, it could be observed that the former has a lower Tafel slope, indicating that its contribution to the catalytic activity is not directly a reduction in overpotential, although it may be contributing to a different aspect of catalytic activity beyond the overpotential.\u003c/p\u003e\u003cp\u003eThe long-term stability and durability of an electrocatalyst is a critical requirement for electrochemical applications. The stability of the (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) sample was determined through a 1,000-cycle test through cyclic voltammetry. The first cycle was not utilized for comparison as the plot still needed to be considered stable and contained an overshoot. The CV plots of (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) for 5 cycles, 500 cycles, and 1,000 cycles are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThere is no substantial deviation in the overpotential values after 1,000 cycles, highlighting its excellent stability with negligible losses. It was found that the difference in overpotential from the first 5 cycles to the last cycle is \u0026minus;\u0026thinsp;33.62 mV, indicating that the overpotential was further reduced during the stability test. This can be observed in the horizontal shifting of the voltammogram as more cycles are performed and may indicate the exposure of more active sites. A substantial increase in the Ni hump was observed as the number of cycles increased throughout the test, which is distinguished as the \u0026lsquo;bump\u0026rsquo; before the Faradaic or linear region begins. This implies that more Ni areas were exposed in the stability test, leading to more intense peaks/humps for Ni oxidation. The prolonged oxidation of Ni present in the substrate or in the electrocatalyst itself causes Ni-based electrocatalysts to have decreased electrocatalytic activity over time. Further examination is required to determine at which point the oxidation of Ni causes a decrease in the electrocatalytic activity \u003csup\u003e37\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section3\"\u003e\u003ch2\u003e3.2.2. Electrochemical Impedance Spectroscopy\u003c/h2\u003e\u003cp\u003eThe resistive characteristics of the electrocatalyst are mainly attributed to the interaction of the material surface with the electrolyte, and EIS was used to determine them. The electrochemical impedance was identified using a Nyquist plot with respect to the real resistance.\u003c/p\u003e\u003cp\u003eA Voigt circuit was used to evaluate the system and form the Nyquist plot. This circuit was chosen because it can distinguish the semicircles of the low-frequency and high-frequency regions. The identification of capacitive and resistive properties of the materials follows the Voigt circuit analysis. At low frequencies, capacitive behavior dominates due to diffusion processes \u003csup\u003e38\u003c/sup\u003e. In contrast, diffusion effects are minimized as reactants travel shorter distances at high frequencies \u003csup\u003e38\u003c/sup\u003e. The Nyquist plot of the (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) sample compared to nickel foam substrate itself is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe inclusion of the (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) electrocatalyst resulted in a substantially smaller high-frequency semicircle than that of the nickel foam substrate only. This is because the radii of the electrocatalyst and the nickel foam substrate only are 15.5 Ω and 53.12 Ω, respectively. The diminishing size of the radius is indicative of a lower charge transfer resistance being present between the electrode/electrolyte interface. According to Ahmadian et al. \u003csup\u003e39\u003c/sup\u003e, lower resistance is also indicative of higher catalytic property. This means that the presence of the catalytic component in the Ni foam is an improvement over the substrate only.\u003c/p\u003e\u003cp\u003eThe Ohmic drop is associated with the current flow in the electrolyte and is determined through EIS. The Ohmic drop and charge transfer resistance are associated with intrinsic resistances associated with the material. Although the latter is generally expressed as a pseudo-overpotential, it tends to slightly increase the overpotential associated with a current observed on cyclic voltammograms \u003csup\u003e40\u003c/sup\u003e. It was found that the Ohmic drops are 0.7516 Ω and 1.29 Ω for the synthesized electrocatalyst and the nickel foam, respectively. A lower Ohmic drop is preferred as it indicates better conductivity between the electrode and the electrolytic solution \u003csup\u003e41\u003c/sup\u003e. The Ohmic drop of the electrocatalyst is therefore preferable and indicates an improvement in the facilitation of the OER.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Comparison of Results\u003c/h2\u003e\u003cp\u003eIn comparison to other studies, Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e show the summary of the overpotential and Tafel slope values of different nickel-cobalt selenide electrocatalysts with different materials and substrates used.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of overpotential and Tafel slope values of different NiCoSe electrocatalysts\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNo.\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCatalyst\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSubstrate\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eOverpotential (mV) at\u003c/p\u003e\u003cp\u003e10 mA-cm\u003csup\u003e-2\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eTafel Slope\u003c/p\u003e\u003cp\u003emV-dec\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eReference\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNi\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNickel Foam (NF)\u0026thinsp;+\u0026thinsp;Hydrochar\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e295.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e72.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eThis work\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNiCoSe\u003csub\u003e2\u003c/sub\u003e nano-brush\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e274\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e61.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eXia et al. \u003csup\u003e42\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNiCo\u003csub\u003e2\u003c/sub\u003eSe\u003csub\u003e4\u003c/sub\u003e nanowire\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGlassy Carbon\u003c/p\u003e\u003cp\u003eElectrode (GCE)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e270\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eJeghan \u0026amp; Gibaek \u003csup\u003e43\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNiCo\u003csub\u003e2\u003c/sub\u003eSe\u003csub\u003e4\u003c/sub\u003e nanoarray\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCarbon Cloth (CC)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e340\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eYu et al. \u003csup\u003e44\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNiCo\u003csub\u003e2\u003c/sub\u003eSe\u003csub\u003e4\u003c/sub\u003e nanosheet\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e183\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eAkbar et al. \u003csup\u003e45\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNi\u003csub\u003e0.25\u003c/sub\u003eCo\u003csub\u003e0.75\u003c/sub\u003eSe\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e269\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eLiu et al. \u003csup\u003e46\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNiCoSe\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSulfoselenide/Black Phosphorus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e285\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e116\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eLiang et al. \u003csup\u003e47\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNiSe\u003csub\u003e2\u003c/sub\u003e Nanocrystals\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eKwak et al. \u003csup\u003e48\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eIrO\u003csub\u003e2\u003c/sub\u003e (\u003cem\u003efor comparison\u003c/em\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e310\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eLan et al. \u003csup\u003e14\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eNickel-cobalt selenide electrocatalysts using NF as the substrate have superior OER performance, compared to the catalysts that use other materials as substrate, in terms of overpotential and Tafel slope values. Moreover, the performance of the synthesized electrocatalyst in this work has obtained close overpotential and Tafel slope values to a noble metal-based electrocatalyst (IrO\u003csub\u003e2\u003c/sub\u003e) based on Lan et al. \u003csup\u003e14\u003c/sup\u003e. Comparing the synthesized catalyst with the commercial noble metal-based catalyst (IrO\u003csub\u003e2\u003c/sub\u003e), there was an improvement in the electrocatalytic performance represented by a decrease in the overpotential value. The synthesized catalyst exhibited a 4.56% lower overpotential with a slightly higher Tafel slope (4.56% higher) over a commercial IrO\u003csub\u003e2\u003c/sub\u003e catalyst. Furthermore, these values are within 15% of the average between a sample of performance data from similar NiCoSe-based catalysts, indicating that the synthesized catalyst has comparable performance with the IrO\u003csub\u003e2\u003c/sub\u003e catalyst. However, the synthesis of Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e + HC\u0026thinsp;+\u0026thinsp;NF in this study has a higher Tafel slope value compared to other electrocatalysts. This may be attributed to the composition and distribution of Ni and Co relative to the Se in the compounds. Based on Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the OER performance of the synthesized catalyst is most comparable to the results of Liu et al. \u003csup\u003e46\u003c/sup\u003e. Although the overpotential is higher by 9.98%, the obtained value of the Tafel slope is lower by 2.5%, which is attributed to the presence of HC in the electrocatalyst. The hydrochar in the synthesized catalyst may have contributed to having improved conductivity and higher surface area for its OER performance.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe synthesized Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e supported on hydrochar produces enhanced electrocatalytic activity for the oxygen evolution reaction. The electrocatalyst composition identified from analyzing the main effects, Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e with a 1:1 doped hydrochar ratio (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01), exhibited a low overpotential and high current density, indicative of improved performance over other tested compositions. The 1:1 loading ratio of hydrochar to NiCoSe was found to be desirable, balancing the availability of active sites with the structural support provided by the hydrochar. SEM results confirm the well-dispersed nickel, cobalt, and selenium distribution on the hydrochar support. Furthermore, the EDS confirmed the presence of nickel, cobalt, and selenium elements in the desired ratios, indicating the successful synthesis of the NiCoSe electrocatalyst on the hydrochar support. The use of hydrochar provided additional surface support that expanded the number of active sites, while its combination with the PVP led to the spherical agglomeration of the subsurface that increased the inherent porosity of the electrocatalyst.\u003c/p\u003e\u003cp\u003eThe effect of NiCo:Se ratio, loading, and hydrochar-to-electrocatalyst ratio can be further explored and optimized in future works. As this study only identified the parameters that resulted in an overall lower overpotential, a succeeding study may explore optimizing the interactions between these parameters. The activity and stability of the electrocatalyst may also be explored in acidic media, while stability may also be further studied through an extended-period electrolysis test. The use of the synthesized electrocatalyst may also be explored in the hydrogen evolution reaction, in conjunction with the OER or on its own.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data collected and analyzed for the present study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors acknowledge Dr. Jose Paolo Bantang of the Department of Chemistry for providing the chitin sample necessary for the preparation of hydrochar, Dr. Joan Candice Ondevilla of the Department of Chemistry for their assistance in the FTIR characterization.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding Declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research work is funded by the De La Salle University Science Foundation, Research Grants and Management Office (RGMO) – University Research Coordination Office (URCO).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eJoaquin Nathaniel A. Perez\u003c/strong\u003e: Writing - Original Draft, Writing - Review \u0026amp; Editing, Investigation, Visualization. \u003cstrong\u003eChris Ivan B. Sungcang:\u003c/strong\u003e Writing - Original Draft, Writing - Review \u0026amp; Editing, Investigation, Visualization. \u003cstrong\u003ePatricia Isabel R. Soriano\u003c/strong\u003e: Writing - Original Draft, Data Curation, Investigation, Visualization. \u003cstrong\u003eGio Jerson C. Almonte\u003c/strong\u003e: Writing - Original Draft, Investigation, Visualization. \u003cstrong\u003eAngelo Earvin Sy Choi\u003c/strong\u003e: Supervision, Project Administration, Resources. \u003cstrong\u003eJoseph R. Ortenero\u003c/strong\u003e: Funding acquisition, Supervision, Project Administration, Conceptualization, Methodology, Resources.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eInternational Energy Agency. \u003cem\u003eRenewables 2024\u003c/em\u003e. (2024).\u003c/li\u003e\n\u003cli\u003eREN21. \u003cem\u003eRenewables 2022 Global Status Report\u003c/em\u003e. (2022).\u003c/li\u003e\n\u003cli\u003eSoriano, P. 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Interfaces\u003c/em\u003e \u003cstrong\u003e8\u003c/strong\u003e, 5327\u0026ndash;5334 (2016).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Nickel-Cobalt Selenide, Hydrochar Support, Oxygen Evolution Reaction, Overpotential Reduction, Transition Metal Chalcogenides, Electrocatalysis, Green Hydrogen Production","lastPublishedDoi":"10.21203/rs.3.rs-7450657/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7450657/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study explores the development and characterization of a nickel-cobalt selenide (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) electrocatalyst supported on hydrochar and nickel foam for the oxygen evolution reaction (OER) in alkaline water electrolysis. NiCoSe is synthesized through electrodeposition and subsequently dispersed on hydrochar. The NiCoSe/hydrochar is drop cast on a nickel foam substrate to serve as the anode. The electrocatalyst is characterized through SEM-EDS, XRD, and FTIR. The activity and stability are evaluated using CV, LSV, and EIS. XRD patterns show the formation of the mixed metal selenides, while SEM micrographs reveal the presence of microstructures that enhance the surface area of the catalyst. Elemental mapping of the NiCoSe/hydrochar shows the uniform distribution of Ni, Co, and Se. The synthesized catalyst (Ni\u003csub\u003e0.6\u003c/sub\u003eCo\u003csub\u003e0.4\u003c/sub\u003eSe\u003csub\u003e2\u003c/sub\u003e, 1:1, 0.01) was found to deliver a current density of 10 mA-cm\u003csup\u003e-2\u003c/sup\u003e at an overpotential of 295.85 mV. Compared to the Ni foam alone, this composition shows a substantial improvement in the electrocatalytic activity, likely due to the reconfiguration of the electronic structure of nickel with the presence of cobalt. The presence of hydrochar contributes to a 6.55% reduction in the overpotential at 10 mA-cm\u003csup\u003e-2\u003c/sup\u003e, highlighting its potential as a carbon support for dispersing the electrocatalyst and allowing for greater exposure of the active sites. A low Tafel slope of 72.15 mV-dec\u003csup\u003e-1\u003c/sup\u003e further indicates high electrocatalytic activity, aligning with the performance of other Ni\u003csub\u003ex\u003c/sub\u003eCo\u003csub\u003ey\u003c/sub\u003eSe\u003csub\u003ez\u003c/sub\u003e electrocatalysts. This study demonstrates that nickel-cobalt selenide can effectively lower the high overpotential of the OER, although further enhancement is needed in the conductivity of hydrochar.\u003c/p\u003e","manuscriptTitle":"Hydrochar-Supported Nickel-Cobalt Selenide Electrocatalyst for Enhanced Oxygen Evolution Reaction Performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-11 12:49:32","doi":"10.21203/rs.3.rs-7450657/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-06T16:46:41+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-06T09:52:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"232817895149554732642861003030849756903","date":"2025-09-29T04:20:48+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-26T04:37:22+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-12T08:30:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"302965607363129277796927392410833070720","date":"2025-09-12T08:17:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"206330988828517737135328295938199950792","date":"2025-09-12T06:50:54+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-05T09:03:01+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-04T22:01:05+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-04T13:08:11+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-02T19:40:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-09-02T19:37:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"bcbc63b2-fcc1-4026-8b9c-d5a9a0e3fa7c","owner":[],"postedDate":"September 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[{"id":54248485,"name":"Physical sciences/Chemistry"},{"id":54248486,"name":"Physical sciences/Energy science and technology"},{"id":54248487,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2025-10-06T16:53:17+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-11 12:49:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7450657","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7450657","identity":"rs-7450657","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}