Electrochemical Hydrogen Evolution Reaction Research Articles

Tuning Intermediate-Enriched microenvironment of pt-loaded porous TiN nanorods for enhanced electrochemical ozone production and hydrogen evolution reaction

Electrochemical ozone production (EOP) is a technology with great promise for ozone synthesis, where electrochemical anode and cathode reactions play key roles in electrolytic ozone generators. In this work, mesoporous three-dimensional Pt/TiN nanorods (NRs) have been designed and prepared for EOP and HER, exhibited impressive performance with the faraday efficiency of the anodic EOP was 13 %. The overpotential of cathodic HER was 38 mV at 10 mA·cm−2 with 0.5 M H2SO4. The porous structure of Pt/TiN NRs provides microenvironments favorable for enrichment of reaction intermediates, accelerating the kinetic processes of EOP and HER. Theoretical calculations have revealed that metal-support interactions (MSI) between Pt and TiN play an influential role in the adsorption of reactive intermediates. Furthermore, promising efficiencies in the electrochemical degradation of organic pollutants have been investigated, highlighting the potential application of the Pt/TiN NRs-1 || Pt/TiN NRs-2 in advanced electrochemical oxidation.

Transition metal carbide‐based nanostructures for electrochemical hydrogen and oxygen evolution reactions

AbstractExtensive consumption of limited fossil fuel resources generates serious environmental problems, such as release of large amounts of the greenhouse gas CO2. It is, therefore, urgently necessary to look for alternative energy resources to meet increasing energy demands. Hydrogen is a clean, environmentally friendly, and sustainable energy source. Electrochemical water splitting is one of the cleanest and greenest technologies available for hydrogen production. Unfortunately, large‐scale water electrolysis is hindered by the high costs of catalysts, since noble metal‐based materials have been demonstrated to be the best catalysts (e.g., Pt for the cathode and Ru/Ir‐oxide for the anode catalyst). Recently, transition metal carbides (TMCs) have drawn significant attention for use in electrochemical water splitting, especially for hydrogen evolution reactions, owing to their high intrinsic catalytic activities, extraordinary electrical conductivities, and abundant source materials. TMCs exhibit Pt‐like electronic structures and are considered suitable alternatives for Pt. This review systematically summarizes recent advances in the uses of representative TMCs for the electrochemical hydrogen and oxygen evolution reactions and highlights advantages in the electrocatalytic effects provided by nanostructuring. Finally, existing challenges and future perspectives for use of these electrocatalysts are discussed.

An Overview of Metal-organic Framework Based Electrocatalysts: Design and Synthesis for Electrochemical Hydrogen Evolution, Oxygen Evolution, and Carbon Dioxide Reduction Reactions.

Due to the increasing global energy demands, scarce fossil fuel supplies, and environmental issues, the pursued goals of energy technologies are being sustainable, more efficient, accessible, and produce near zero greenhouse gas emissions. Electrochemical water splitting is considered as a highly viable and eco-friendly energy technology. Further, electrochemical carbon dioxide (CO2 ) reduction reaction (CO2 RR) is a cleaner strategy for CO2 utilization and conversion to stable energy (fuels). One of the critical issues in these cleaner technologies is the development of efficient and economical electrocatalyst. Among various materials, metal-organic frameworks (MOFs) are becoming increasingly popular because of their structural tunability, such as pre- and post- synthetic modifications, flexibility in ligand design and its functional groups, and incorporation of different metal nodes, that allows for the design of suitable MOFs with desired quality required for each process. In this review, the design of MOF was discussed for specific process together with different synthetic methods and their effects on the MOF properties. The MOFs as electrocatalysts were highlighted with their performances from the aspects of hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and electrochemical CO2 RR. Finally, the challenges and opportunities in this field are discussed.

Electrochemical activation of CoMo LDH nanosheets driving surface reconstruction for enhanced hydrogen evolution

Surface reconstruction emerging in the electrochemical oxygen evolution process is regarded to be significantly important for the activated catalysis efficiency, however, which is rarely recognized for hydrogen evolution reaction (HER). Here, the electrochemical activation of CoMo layered double hydroxide (CoMo-LDH) nanosheet arrays is demonstrated to significantly activate the electrochemical HER property. The catalysis performance improvement originates from the surface transformation of CoMo-LDH to Co(OH)2/CoOOH, as well as the dissolution of Mo and its adsorption on the catalyst surface in K2Mo3O10 phase. Based on the combined benefits of optimized electronic structure, increased catalysis sites, and promoted charge transfer, the overpotentials at catalysis current densities of 10 and 100 mA cm−2 are as low as 113 and 202 mV. This study demonstrates the electrochemical activation strategy to drive the surface reconstruction of bimetal hydroxides for enhanced HER performance, inspiring the research interests on the reconstruction and activation enhancement behaviors of HER electrocatalysts.

Mechanistic understanding on effect of doping nitrogen with graphene supported single-atom Ir toward HER and OER: A computational consideration

The electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) hold tremendous potential as pathways for generating clean energy. In this study, we conducted comprehensive density functional theory (DFT) calculations to investigate the influence of nitrogen (N) dopants, in terms of their types (Pyrrolic-N and Pyridinic-N) and concentrations, on the performance of 2D graphene-based catalysts containing single atoms of iridium (Ir SACs) for HER and OER. Our computational results demonstrate that the incorporation of N dopants into graphene-based supports significantly enhances the stability of Ir SACs. The bonding strength between the individual Ir atoms and the support material increases as the N content rises. Moreover, as the number of N dopants increases, the electron loss from Ir decreases. Notably, Ir-3-N1-Pi exhibits superior HER performance with a ΔGH* value of 0.24 eV, while Ir-4-N4-Po demonstrates excellent OER performance with an overpotential (η) of 0.47 V. By understanding the influence of N dopants, this study can pave the way for better tailor graphene-based catalysts for enhanced HER and OER performance, thus advancing the development of clean and sustainable energy technologies.

Siderophore mediated in vitro synthesis of electrocatalytic nanocrystallite struvite variants for highly efficient and durable hydrogen evolution reaction

We report in vitro nanocrystallite variants of Ni and Co struvite formed by bacterial siderophore using the green synthesis method. Assembling of siderophore mediated nanocrystallite struvite variants in the presence of Mg2+, Ni2+ and/or Co2+ and PO43− ions (pH- 9.0) has been investigated. The nanocrystallite struvite was characterized by field emission scanning electron microscopy with energy dispersive X-ray spectroscopy. Fourier transform infrared spectroscopy, Raman spectroscopy for their structural, and X-ray powder diffraction for its crystal structure in conjunction with density functional theory. A strategy described here can be explored for rapid synthesis and a large-scale production of modified struvite nanocrystallite materials. Moreover, the potential implications of siderophore accompanying the struvite variant formation facilitated by sequestering electroactive metal ions are discussed. More importantly, the Ni struvite variant demonstrated high electrochemical hydrogen evolution reaction (HER) with overpotential of −59 mV at 10 mA/cm2 current density which is at par with the benchmark Pt electrocatalysts. The stability of Ni struvite during the HER at overpotential and at 100 mA/cm2 applied current density has been demonstrated.

Proton Relay for the Rate Enhancement of Electrochemical Hydrogen Reactions at Heterogeneous Interfaces.

Proton transfer is critically important to many electrocatalytic reactions, and directed proton delivery could open new avenues for the design of electrocatalysts. However, although this approach has been successful in molecular electrocatalysis, proton transfer has not received the same attention in heterogeneous electrocatalyst design. Here, we report that a metal oxide proton relay can be built within heterogeneous electrocatalyst architectures and improves the kinetics of electrochemical hydrogen evolution and oxidation reactions. The volcano-type relationship between activity enhancement and pKa of amine additives confirms this improvement; we observe maximum rate enhancement when the pKa of a proton relay matches the pH of the electrolyte solution. Density-functional-theory-based reactivity studies reveal a decreased proton transfer energy barrier with a metal oxide proton relay. These findings demonstrate the possibility of controlling the proton delivery and enhancing the reaction kinetics by tuning the chemical properties and structures at heterogeneous interfaces.

Influence of antisite defects on two-dimensional polymeric material for improved hydrogen evolution reaction

Two-dimensional materials (2D) supported by single atom catalysis have emerged as effective catalysts for H2 production at large scale by Hydrogen Evolution Reaction (HER). While there is a research surge on utilizing inexpensive metals as catalysts to replace Platinum (Pt) and other related noble metals, their practical limitations such as oxidation issues remain a concern. In this work, we report electrochemical HER activity of a recently synthesized metal-free 2D Polyaramid (2DPA) using Density Functional Theory (DFT) calculations. Pristine 2DPA exhibits remarkable HER performance in terms of active sites availability for hydrogen adsorption and the lowest Gibb's free energy change (−0.06 eV) close to that of benchmark Pt/C catalyst (−0.09 eV). Furthermore, introduction of antisite defects by substituting carbon for nitrogen (CN) and nitrogen for carbon (NC) in pristine 2DPA depicts enhanced HER activity. CN and NC defects tune the electronic properties by reducing the band gap resulting improved conductivity. Low formation energies calculated for obtaining antisite defects confirm their feasibility of synthesis while ab initio molecular dynamics (AIMD) simulations ensure their thermal stability at room temperature. The change in Gibb's free energy (ΔGH) values for CN-defective and NC-defective 2DPA are computed to be −0.13 eV and −0.11 eV, respectively. Both CN-defective and NC-defective 2DPA favor H2 evolution via Heyrovsky reaction pathways due to their relatively lower activation energy, 0.64 eV and 0.51 eV, respectively. Our findings encourage design and development of a novel 2D metal-free electrocatalyst for enhanced HER.

G-C3N4/Bromocobaloxime nanocomposites as multi-functional electrocatalysts for water splitting and energy storage

The depletion of fossil fuels necessitates the search for alternative sources of energy and energy storage for long-term usage. Recently graphitic carbon nitride (g-C3N4) based materials have gained attention due to their enhanced activity compared to previously tested materials. But the poor electron mobility of g-C3N4 continues to cause a significant energy loss in the electrocatalytic processes. Herein we report the synthesis and characterization of g-C3N4/Bromocobaloxime composites and their electrocatalytic applications towards hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and energy storage. Bromocobaloximes [BrCo(dpgH)2B] (B1-B4) containing diphenylglyoxime [dpgH] as the equatorial ligand and functionalized neutral bases such as Isonicotinic acid (1), Pyridine-3,5-dicarboxylic acid (2), Indole-2-carboxylic acid (3) and p-Aminobenzoic acid (4) were synthesized using the standard procedure. The g-C3N4/Cobaloxime nanocomposites (g-C3N4/B1, g-C3N4/B2, g-C3N4/B3 and g-C3N4/B4) were prepared using g-C3N4 nanosheets by solvothermal method. The prepared nanocomposites were characterized by FT-IR, UV-DRS, XRD, SEM, EDAX, TEM and XPS analysis. The electrochemical HER studies of the synthesized nanocomposites showed low overpotentials in the range of 51 to 228 mV at −10 mAcm−2 and the OER studies exhibited overpotentials in the range of 310 to 460 mV at 10 mAcm−2. Among them nanocomposite g-C3N4/B2 showed a lower Tafel slope of 45 mV/dec for HER and 112 mV/dec for OER. The supercapacitance studies indicated that among the nanocomposites, g-C3N4/B1 showed a good specific capacitance of 302 F/g at 0.5 A/g. The increased electrochemical performance of the synthesized nanocomposites is due to the incorporation of cobaloximes containing carboxylic acid functionalized neutral bases into the g-C3N4 nanosheets, which increases the electron mobility. This will lead to explore the applications of g-C3N4/metal complexes towards energy conversion by tuning the ligands in the metal complexes.

Ni-Ti3C2 MXene composite derived from Ni-metal organic framework for electrochemical hydrogen evolution reaction in acidic and alkaline medium

MOFs derived metal composites are found to be a potential electrocatalyst for energy storage and conversion process. In this work, Ni composite with MXene (Ni-Ti3C2) was synthesized by calcination of Ni-MOF at 650 °C and characterized by XRD, FE-SEM, FTIR and BET analysis. After calcination, the derived Ni composited Ti3C2 showed a high porosity and high surface area as compared to Ti3C2. The derived material was further used as electrode for Hydrogen Evolution Reaction (HER) and tested by various electrochemical analysis viz. Cyclic voltammetry (CV), Electrochemical impedance analysis (EIS) and Linear Sweep Voltammetry (LSV) in alkaline medium. The derived Ni-Ti3C2 in basic medium displays a small Tafel value of 56.15 mV/dec with acquired voltage of 181.15 mV due to the surface area and accessible catalytic active sites, which provides excellent mass transfer properties for derived Ni-Ti3C2 composite in basic medium. The kinetics of the HER reaction was found better in Ni-Ti3C2 MXene composite in basic medium than in acidic medium. The charge transfer resistances were obtained from the EIS plot and were found to be 3.98 Ω and 2.34 Ω for Ti3C2 and Ni-Ti3C2 respectively in acidic medium and 3.12 Ω and 1.98 Ω in basic medium. The low resistance observed for Ni-Ti3C2 in basic medium proves a higher electrocatalytic activity in Ni-Ti3C2 than Ti3C2. The cyclic stability of the Ni-Ti3C2 in basic medium was higher than Ti3C2. Thus the overall results show that the prepared composite is a potential catalyst for HER applications.

Defect-rich 1T-MoS2 nanosheets towards efficient electrochemical hydrogen evolution by simultaneous phase and defect engineering

Molybdenum sulfide (MoS2) has been considered as a promising candidate to replace Pt for the electrochemical hydrogen evolution reaction (HER). However, the disadvantages of inert basal planes and low conductivity limit its application in HER. Herein, we report a facile strategy to achieve simultaneous phase transition and defect engineering in MoS2 by adjusting the ratio of sulfur precursor to molybdenum precursor in the synthesis process. The excess thiourea are adsorbed on the surface of as-formed MoS2 nanocrystallites, which hinders the further crystallization process and creates a large amount of defects on the basal planes. Besides, ammonia ions could in situ insert into the interlayers of MoS2 and induce a phase transition from 2H–MoS2 to 1T-MoS2. The optimized defect-rich 1T-MoS2 catalyst shows a small overpotential of 232 mV at 10 mA cm−2 and Tafel slope of 61 mV dec−1 in acidic media. The superior HER activity is attributed to the defect-rich and 1T-phase structure, which contributes significantly enhanced electronic conductivity and greatly exposed active sites.

Modulating Force of Nucleated Hydrogen Bubble Adhesion to Boost Electrochemical Water Splitting

AbstractIn electrochemical hydrogen evolution reaction (HER), the produced hydrogen gas bubbles often adhered to the electrode surface and blocked the active catalytic site. While different catalysts are developed to improve the catalytic performance of HER, the design of a durable and universal approach for minimizing the force of nucleated hydrogen gas‐bubble adhesion to prevent blockage of electrocatalytic sites because of bubbles‐adhesion is unprecedented. Generally, buoyancy should outweigh the capillary force to remove nucleated bubbles, which means these forces ratio, Eötvös number Eo > 1. Herein, a chemically reactive multilayer coating on an electrode is reported to chemically modulate the adhesion force of nucleated gas‐bubble on the electrode. A dual modified coating on Ni‐foam provided a non‐adhesive superaerophobicity with nucleated bubble adhesion force of 4.6 ± 0.3 µN and displayed superior HER performance with lower overpotential (333 to 250 mV) at 100 mA cm−2 with respect to bare Ni‐foam. The chemically‐modulated low bubble‐adhesion facilitates the early removal of nucleated tiny hydrogen gas bubbles with a minimum size of 0.64 mm and Eo = 0.05 to keep catalytic sites available for superior electrochemical HER. Such a positive impact of the prepared coating is also noted for various other electrodes.

ΜοS2 nanoensembles prepared by a simple solvothermal route for hydrogen evolution reaction

Electrochemical hydrogen evolution reaction (HER) is an emerging research domain aiming to supply a means of renewable energy. Transition metal dichalcogenides (TMDs) have a good potential as promising low-cost alternatives to platinum-based catalysts. Molybdenum disulfide (MoS2) nanostructures with different shapes are increasingly becoming attractive materials for HER electrocatalysis, thanks to their peculiar physical properties which depend on their composition and morphology. It is still challenging to produce MoS2 nanomaterials simply and straightforwardly. In this work, MoS2 nanoensembles and small nanoparticles were fabricated via facile solvothermal protocols. The produced structures display a competitive activity in HER, with the nanoensembles performing better than the isotropic particles. This was attributed to the abundance of their electrochemically active sites and their robust structural stability, which endowed them with remarkable endurability in electroactivity. The nanoensemble morphology ensured the creation of a well-connected array of channels for charge transport, thus favouring an ameliorated electrochemical activity.

Electrochemical Hydrogen Evolution Reaction Evaluation of CoNi(Cr/V) Medium-Entropy Alloys in an Acidic Environment

Electrochemical Hydrogen Evolution Reaction Evaluation of CoNi(Cr/V) Medium-Entropy Alloys in an Acidic Environment

A general protocol for precise syntheses of ordered mesoporous intermetallic nanoparticles.

Intermetallic nanomaterials consist of two or more metals in a highly ordered atomic arrangement. There are many possible combinations and morphologies, and exploring their properties is an important research area. Their strict stoichiometry requirement and well-defined atom binding environment make intermetallic compounds an ideal research platform to rationally optimize catalytic performance. Making mesoporous intermetallic materials is a further advance; crystalline mesoporosity can expose more active sites, facilitate the mass and electron transfer, and provide the distinguished mesoporous nanoconfinement environment. In this Protocol, we describe how to prepare ordered mesoporous intermetallic nanomaterials with controlled compositions, morphologies/structures and phases by a general concurrent template strategy. In this approach, the concurrent template used is a hybrid of mesoporous platinum or palladium and Korea Advanced Institute of Science and Technology-6 (KIT-6) (meso-Pt/KIT-6 or meso-Pd/KIT-6) that can be transformed by the second precursors under reducing conditions. The second precursor can either be a second metal or a metalloid/non-metal, e.g., boron/phosphorus. KIT-6 is a silica scaffold that is removed using NaOH or HF to form the mesoporous product. Procedures for example catalytic applications include the 3-nitrophenylacetylene semi-hydrogenation reaction, p-nitrophenol reduction reaction and electrochemical hydrogen evolution reaction. The synthetic strategy for preparation of ordered mesoporous intermetallic nanoparticles would take almost 5 d; the physical characterization by electron microscope, X-ray diffraction and inductively coupled plasma-mass spectrometry takes ~2 days and the function characterization depends on the research question, but for catalysis it takes 1-5 h.

Facile and Cost-effective Synthesis of CoP@N-doped Carbon with High Catalytic Performance for Electrochemical Hydrogen Evolution Reaction.

The manufacture of efficient and low-cost hydrogen evolution reaction (HER) catalysts is regarded as a critical solution to achieve carbon neutrality. Herein, we developed an economical method to synthesize a CoP-anchored N-doped carbon catalyst via one-step pyrolysis using inexpensive starting materials (cobalt ion salt, phytic acid, and glycine). The size of the CoP nanoparticles was controlled by adjusting the Co/P ratio of the catalysts. Nanoscale CoP particles with adequate exposure to active sites were uniformly anchored on the surface of the conductive nitrogen-doped carbon substrate, ensuring the rapid transfer of electrons and species. When Co/P=0.89, the as-made catalyst exhibited outstanding HER activity, with an extraordinarily low overpotential of 202 mV at 10 mA cm-2 and long-term stability.

Highly active Mo-modified NiCoP/NiCoN flower-like sphere: Controlled phase engineering for efficient water splitting

Reasonable design and preparation of a versatile catalyst for the ultra-high efficiency energy conversion system has remarkable practical significance. Herein, a facile phase engineering strategy is employed to synthesize molybdenum modified nickel cobalt nitride and nickel cobalt phosphide flower-like sphere heterostructure (labeled as Mo-NiCoP/NiCoN FS) to improve the performance of Mo-NiCoN FS. The significant geometric structure advantages, the exposure to abundant active centers and the interfacial effect of heterostructure of the target product is evaluated in detail. When the as-obtained Mo-NiCoP/NiCoN FS is applied to the electrochemical bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), it demonstrates remarkable electrocatalytic activity, high-conductivity and excellent corrosion resistance compared with Mo-NiCoN FS with a single phase. As a result, Mo-NiCoP/NiCoN FS indicates a low overpotential towards HER (204 mV at 10 mA/cm2) and OER (262 mV at 10 mA/cm2) compared with Mo-NiCoN (234 mV for HER and 357 mV for OER at 10 mA/cm2) in an alkaline medium and it exhibits excellent activity and stability during the dual-electrode full water-splitting. Therefore, the advanced nano-catalyst with superior activity developed through the controllable phase engineering method illustrates a potential application prospect in high efficiency energy equipment water-splitting and fuel-cells.

Alkynyl-protected Ag20 Rh2 Nanocluster with Atomic Precision: Structure Analysis and Tri-functionality Catalytic Application.

We report the overall structure and trifunctionality catalytic application of an atomically precise alloy nanocluster of Ag20 Rh2 (C≡C-t Bu)16 (CF3 CO2 )6 (H2 O)2 (abbreviated as Ag20 Rh2 hereafter). Ag20 Rh2 has a twisted rod-like structure, where a Ag4 @Rh2 kernel is connected by two twisted Ag8 cubes on two sides. Ag20 Rh2 is a superatomic cluster with four free valence electrons, and it has characteristic absorbance feature. Interestingly, Ag20 Rh2 exhibited superior catalytic performance than the larger AgRh nanoparticle counterparts in electrochemical hydrogen evolution reaction (HER), reduction of 4-nitrophenol, and the methyl orange degradation reaction. Such intriguing catalytic properties are attributed to the more exposed active sites from the ultrasmall nanoclusters than relatively large nanoparticles. This study not only enriches the family member of alkynyl-protected AgRh nanoclusters with atomic precision, but also highlights the great advantages of employing nanoclusters as efficient catalysts for multiple functionalities.

Re-Structuring of Interfacial Water into Strongly Hydrogen Bonded “Ice-like” Structures as the Unifying Descriptor for Improving Sluggish HOR/HER in Alkaline Electrolyte

The 2 orders of magnitude loss of Platinum Group Metal (PGM) activity toward Hydrogen Oxidation and Reduction reactions (HOR/HER) has hindered implementation of alkaline based electrolyzers and fuel cells and demonstrated a significant knowledge gap in our fundamental understanding of electrochemical interfaces.1 Beneath the seemingly simple reaction lies a potentially convoluted mechanism, with various researchers assigning the activity loss to shifts in electrode potential of zero free charge,2 changed binding energies of adsorbates and reactive intermediates,3,4 and the re-arrangement of interfacial water.5 Recently, Monteiro et al. showed an activity dependence on interfacial cation concentration and identity, suggesting that charge dense cations are able to better stabilize the OH- produced from the unfavorable but necessary water splitting in the HER direction near the negatively charged surface.6,7 In this work, we challenge this notion by demonstrating that competition for water molecules between Outer Helmholtz Plane (OHP) cations and the interfacial water structure is responsible for the activity loss. Through the use of traditional Rotating Disk Electrode, in situ Attenuated Total Reflection-Surface Enhanced Infrared Reflection Absorption Spectroscopy (ATR-SEIRAS) and judicious choice of crown ether additives to hinder the water-interfacial cation interaction, we show a positive correlation between the strength and number of interfacial water-water hydrogen bonds and platinum’s HOR/HER activity.The typical double layer structure in an aqueous electrochemical system consists of specifically adsorbed species in the Inner Helmholtz Plane (IHP), the first layer of non-adsorbates at the OHP, and water hydrating the charged species. ATR-SEIRAS has previously been used to analyze the structure of these hydration shells on a CO covered Pt surface, demonstrating hydrating waters interacting mainly with alkali metal cations through the increase of a 3600 cm-1 ν(O-H) stretch and weak interactions with surrounding interfacial water.8 Through chelation with crown ether, these hydration shells convert from strongly to weakly cation interacting, favoring instead hydrogen bonding with other water molecules, shown with increasing absorption bands at lower wavenumbers (3400 cm-1). This transition is accompanied by an increase in 3000 cm-1 on the CO-free Pt surface, previously assigned to strongly hydrogen bonded “ice-like” interfacial water.9 We further show a similar increase in the 3000 cm-1 band for other kinetic enhancing additives recently reported in the literature, supporting the notion that increasing water-water hydrogen bonding is the unifying descriptor for promoting a rigid interfacial “ice-like” structure and improving PGM HOR/HER activity. Durst, J. et al. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energy Environ. Sci. 7, 2255–2260 (2014).Sarabia, F. J., Sebastián-Pascual, P., Koper, M. T. M., Climent, V. & Feliu, J. M. Effect of the Interfacial Water Structure on the Hydrogen Evolution Reaction on Pt(111) Modified with Different Nickel Hydroxide Coverages in Alkaline Media. ACS Appl. Mater. Interfaces 11, 613–623 (2019).McCrum, I. T. & Koper, M. T. M. The role of adsorbed hydroxide in hydrogen evolution reaction kinetics on modified platinum. Nat. Energy 5, 891–899 (2020).Yang, X., Nash, J., Oliveira, N. J., Yan, Y. & Xu, B. Understanding the pH Dependence of Underpotential Deposited Hydrogen on Platinum. Angew. Chemie - Int. Ed. 58, 17718–17723 (2019).Zhao, K. et al. Enhancing Hydrogen Oxidation and Evolution Kinetics by Tuning the Interfacial Hydrogen-Bonding Environment on Functionalized Platinum Surfaces. Angew. Chemie - Int. Ed. 61, (2022).Monteiro, M. C. O., Goyal, A., Moerland, P. & Koper, M. T. M. Understanding Cation Trends for Hydrogen Evolution on Platinum and Gold Electrodes in Alkaline Media. ACS Catal. 11, 14328–14335 (2021).Goyal, A. & Koper, M. T. M. The Interrelated Effect of Cations and Electrolyte pH on the Hydrogen Evolution Reaction on Gold Electrodes in Alkaline Media. Angew. Chemie - Int. Ed. 60, 13452–13462 (2021).Yamakata, A. & Osawa, M. Cation-dependent restructure of the electric double layer on CO-covered Pt electrodes: Difference between hydrophilic and hydrophobic cations. J. Electroanal. Chem. 800, 19–24 (2017).Osawa, M., Tsushima, M., Mogami, H., Samjeské, G. & Yamakata, A. Structure of water at the electrified platinum-water interface: A study by surface-enhanced infrared absorption spectroscopy. J. Phys. Chem. C 112, 4248–4256 (2008). Figure 1

Hydrothermal synthesis of rGO/ZnCoS composite for high performance asymmetric supercapacitor and HER applications

Here, we describe the successful hydrothermal synthesis of zinc cobalt sulfide (ZCS) and reduced graphene oxide/zinc cobalt sulfide (rZCS) nanoparticles (NPs). X-Ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (TEM) characterizations were used to test ZCS and rZCS NPs. Through the use of cyclic voltammetry (CV), galvanostatic charge and discharge (GCD), and electrochemical impedance (EIS), the electrochemical performance of the produced materials was examined. Electrochemical hydrogen evolution reactions and supercapacitor applications required the development of ZCS and rZCS electrodes. 10 mA cm−2 is driven by rZCS electrodes at 132 mV HER overpotential. High specific capacitance of 891 F g−1 at 1 A g−1 current density and 99 % cyclic stability are displayed by the rZCS electrode even after 5000 cycles. The specific capacitance of (181 F g−1 at 1 A g−1 current density), capacitance retention of (92 % after 10,000 cycles at 1 A g−1, and energy and power density of (29 Wh kg−1 and 2215 W kg−1), respectively, are recommended for asymmetric supercapacitors made from cells using rZCS and rGO. Given this, the produced electrodes material holds potential for use in energy storage technologies.