Electrode For Hydrogen Evolution Reaction Research Articles

Optimizing Platinum Location on Nickel Hydroxide Nanosheets to Accelerate the Hydrogen Evolution Reaction.

Rational electrode design is crucial to promote the performance of the hydrogen evolution reaction (HER) via further enhancing the activity, stability, and utilization of platinum (Pt) in an alkaline electrolyte. Herein, a binder-free low-Pt-content HER electrode, Pt (∼20 μg cm-2) decorated on nickel hydroxide grown on nickel foam (Pt-Ni(OH)2-2h-NF20), is fabricated at near room temperature in a test tube. To lower the ohmic resistance, for the first time, the Pt nanoparticles were location-selectively anchored on the bottom of height-controlled vertical Ni(OH)2 nanosheets via utilizing the mass transfer resistance of the dense Ni(OH)2 film for chloroplatinate. Furthermore, the excellent mass transfer, high specific surface area of Pt, synergistic effect between Pt with Ni(OH)2, and stable structure together prompt the resulting electrode with a special structure to exhibit superior HER electrocatalytic activity and stability in 1 M KOH. Typically, this electrode reaches a current density of 35.9 mA cm-2 at an overpotential of 100 mV, which is over 8 times higher than that of commercial Pt/C, and the overpotential only increases by 20 mV at 100 mA cm-2 over 150,000 s of stability test. Benefiting from the simple fabrication process, the electrode with an area of 840 cm2 was successfully prepared with a steady overpotential of 370 mV at 1000 mA cm-2 and increased potential of 23 mV over 50 h of stability test.

Correlation of Exchange Current Density j₀ and the Standard Potential of the Metal Electrodes EM⁰ for the Hydrogen Evolution Reaction (HER)

The hydrogen evolution reaction (HER) is critical technologically in electrochemically energy systems. HER is also important fundamentally as 2H⁺ + 2e ⇌ H₂ provides the standard reference potential E0 H = 0.000 V in thermodynamics and HER serves as a primary and critical test case for kinetics theory.For HER electrocatalytic rates, the mechanism is historically broken down into three steps. The reaction sequence begins with adsorption and reduction of proton to form electrochemically adsorbed hydrogen. This is the Volmer step. H⁺ + e ⇄ Hads (Volmer)After the first Hads is formed, H2 can be formed by two pathways. In the Heyrovsky pathway, a second proton undergoes electrochemical hydrogen adsorption at the same metal atom to form hydrogen gas. Hads + H⁺ + e ⇄ H2 (Heyrovsky)In the Tafel pathway, electrochemically adsorbed hydrogens on adjacent metal atoms react to form H2. Hads + Hads ⇄ H2 (Tafel)HER electrode kinetics measured as exchange current densities j₀ are evaluated in accord with the Volmer-Heyrovsky-Tafel scheme.For HER at metal electrodes, log j₀ is known highly dependent on the metal of the electrodes with rates that vary > 10 orders of magnitude. HER data are evaluated according to these three steps, despite that properties of the metal are not explicit in the Volmer-Heyrovsky-Tafel scheme.Here, properties of the metal electrode are introduced through the standard potential E0 M. For metal M0, Mz+ + ze ⇌ M⁰ E0 M Data for log j₀ are taken from a paper by Trasatti (Electroanalytical Chemistry and Interfacial Electrochemistry (1972) 39, 163-184). Trasatti grouped the 31 metal electrodes into d and sp metals. For the d metals (transition metals), log j₀ is well and linearly correlated with E0 M, whereas for the sp metals, little to no correlation is found.Several points are considered. Higher HER rates are observed at transition metal electrodes with more positive values of E0 M.It is sketched that the initial step in the metal dependent HER process is release of electron(s) to form Mz+ immediately at the electrode surface.Where formation of Mz+immediately at the electrode solution interface is the initial step, log j₀ is anticipated linearly dependent on E0 M.The behavior is sketched within transition state or activated complex theory and is based on a transition state formed of electron(s) shared between the metal cation Mz+ and the proton H+.Formation of the transition state [(1/z)Mz+⋯e⋯H+]‡ precedes the Volmer step, and where applicable, is a rate determining step.Implications for overpotential η pinned by E0 M are considered. This may account for the counter intuitive observation that higher log j₀ are found on metals such as Pt where E0 M is more positive. A kinetic model is sketched where a component of the activation energy is set by F(E0 H-E0 M). Finally, the process of proposing an electrode dependent transition state and evaluating the thermodynamic and kinetic consequences may yield a general method for modeling interfacial electron transfer and electrocatalysis. Such a process may introduces electrode specific properties into the rate expressions a priori.

Lateral silicon oxide/gold interfaces enhance the rate of electrochemical hydrogen evolution reaction in alkaline media.

The production of solar hydrogen with a silicon based water splitting device is a promising future technology, and silicon-based metal-insulator-semiconductor (MIS) electrodes have been proposed as suitable architectures for efficient photocathodes based on the electronic properties of the MIS structures and the catalytic properties of the metals. In this paper, we demonstrate that the interfaces between the metal and oxide of laterally patterned MIS electrodes may strongly enhance the catalytic activity of the electrode compared to bulk metal surfaces. The employed electrodes consist of well-defined, large-area arrays of gold structures of various mesoscopic sizes embedded in a silicon oxide support on silicon. We demonstrate that the activity of these electrodes for hydrogen evolution reaction (HER) increases with an increase in gold/silicon oxide boundary length in both acidic and alkaline media, although the enhancement of the HER rate in alkaline electrolytes is considerably larger than in acidic electrolytes. Electrodes with the largest interfacial length of gold/silicon oxide exhibited a 10-times larger HER rate in alkaline electrolytes than those with the smallest interfacial length. The data suggest that at the metal/silicon oxide boundaries, alkaline HER is enhanced through a bifunctional mechanism, which we tentatively relate to the laterally structured electrode geometry and to positive charges present in silicon oxide: Both properties change locally the interfacial electric field at the gold/silicon oxide boundary, which, in turn, facilitates a faster transport of hydroxide ions away from the electrode/electrolyte interface in alkaline solution. This mechanism boosts the alkaline HER activity of p-type silicon based photoelectrodes close to their HER activity in acidic electrolytes.

Ultrathin-layered MoS2 hollow nanospheres decorating Ni3S2 nanowires as high effective self-supporting electrode for hydrogen evolution reaction

High-activity and cost-effective transition metal sulfides (TMSs) have attracted tremendous attention as promising catalysts for hydrogen evolution reaction (HER). However, a significant challenge is the simultaneous construction of abundant electrochemical active sites and the fast electronic transmission path to boost a high-efficient HER. Herein, we demonstrate a facile one-step hydrothermal preparation of MoS2 hollow nanospheres decorating Ni3S2 nanowires supported on Ni foam (NF), without any other additional template, surfactant or annealing. In this three-dimensional (3D) heterostructure, the ultrathin-layered MoS2 hollow nanospheres contribute to the promotion of the total surface area and the electrochemical active sites. Meanwhile, the Ni3S2 nanowires are beneficial to the high electrical conductivity. Consequently, the optimized MoS2/Ni3S2/NF-200-24 electrocatalyst presents an extremely superior HER activity to that of individual MoS2/NF and Ni3S2/NF. The HER overpotentials are 85 mV at 10 mA cm−2 and 189 mV at 100 mA cm−2, which are also comparable with the state-of-the-art 20% Pt/C/NF electrode at both low and high current.

Free-standing phosphorous-doped molybdenum nitride in 3D carbon nanosheet towards hydrogen evolution at all pH values

Highly efficient electrocatalysts towards hydrogen evolution reaction (HER) with large current density at all-pH values are critical for the sustainable hydrogen production. Herein, we report a free-standing HER electrode, phosphorous-doped molybdenum nitride nanoparticles embedded in 3-dimentional carbon nanosheet matrix (P-Mo 2 N-CNS) fabricated via one-step carbonization and in-situ formation. The as-prepared catalyst shows free-standing architecture with interconnected porous microstructure. P-doped Mo 2 N nanoparticles with an average diameter of 4.4 nm are well embedded in the 3-dimentional vertical carbon nanosheets matrix. Remarkable electrocatalytic HER performance is observed in alkaline, neutral and acidic media at large current densities. The overpotential of P-Mo 2 N-CNS to drive a current density of 100 mA cm −2 in 0.5 M H 2 SO 4 and 1.0 M PBS is only 181 and 221 mV, respectively. In particular, the current density reaches up to 1000 mA cm −2 at a low overpotential of 256 mV in 1.0 M KOH, much better than that of the commercial Pt/C catalyst. Density functional theory calculations suggest the optimized H sorption kinetics on Mo 2 N after P doping, elucidating the superior activity. A highly efficient free-standing catalyst is prepared for the large-scale and sustainable production of hydrogen from water splitting.

Recent progress in electrode fabrication for electrocatalytic hydrogen evolution reaction: A mini review

Abstract Electrochemical hydrogen evolution reaction (HER) is of great importance for high-efficiency, low-cost production of hydrogen. As the HER activity of catalysts has been significantly improved in recent years, the routings from catalysts to electrodes represent a key step for practical HER applications. In an HER electrode, hydrogen reduction is accomplished by electron transfer, proton diffusion and bubble release. These processes should be taken into account in the design, engineering and fabrication of the electrode. In this review, we begin with a discussion of the correlation between these important issues and the overall electrochemical HER performance, and then summarize recent progress in the design and fabrication of HER electrodes, with a focus on the effects of electrode structure, electrolyte penetration, ion diffusion and bubble adhesion/release on the HER performance. We conclude with a perspective of strategies for further enhancement and the critical challenges for HER electrode fabrication.

Highly disordered cobalt oxide nanostructure induced by sulfur incorporation for efficient overall water splitting

Exploitation of cost-efficient active electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) plays a significant role for scalable electricity-to-hydrogen energy conversion. Crystalline transition metal oxides as the promising non-noble catalysts, however, are often suffering from the large excess overpotential and unsatisfactory performance. To boost their intrinsic catalytic property, we report here an incorporation of electronegative sulfur into crystalline cobalt oxide (S-CoO x ) to create structural disorder via a facile room-temperature ion exchange strategy. Compared with its crystalline form, the disorder in S-CoO x catalyst enables the increased low oxygen coordination and rich defect sites, which endows S-CoO x a superior catalytic activity for both OER and HER in alkali. Intriguingly, a water electrolyser adopting S-CoO x as both OER and HER electrode catalysts requires mere 1.63 V to reach a current density of 10 mA cm −2 in 1 M KOH. This work highlights the effectiveness of designing high-performing electrocatalysts for water electrolysers based on disordered structural materials. • The structurally disordered S-CoO x catalyst was synthesized via a facile room-temperature sulfur ion exchange strategy. • The structurally disordered catalyst shows increased low oxygen coordination and more defect sites. • Experimental and DFT calculation results reveal that a preferable electronic state was generated for the disorderedS-CoO x catalyst. • This novel structurally disordered strategy enables the S-CoO x catalyst a superior catalytic activity for both OER and HER in alkaline electrolyte.

Surface Phosphation of 3D NiCo2O4 Nanowires Grown on Ni Foam as an Efficient Bifunctional Catalyst for Water Splitting

Highly efficient, cost-effective and durable electrocatalysts for water splitting are crucial for energy conversion and storage. Transition-metal phosphides have been proven to be efficient catalysts for water splitting. In this paper, surface phosphation of 3D NiCo2O4 nanowires grown on Ni foam (P-NiCo2O4/NF) have been prepared to investigate the effect of surface phosphating on catalyst activity. XRD and XPS results demonstrate that P element has been decorated on the surface of the NiCo2O4 nanowires. The electrochemical results prove that P-NiCo2O4/NF shows better electrochemical performance than pure NiCo2O4/NF as an electrode for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of water splitting. It achieves a current density of 10[Formula: see text]mA cm2 at an overpotential of 279[Formula: see text]mV and 164[Formula: see text]mV for OER and HER in 1.0[Formula: see text]M KOH electrolyte, respectively. In addition, the P-NiCo2O4/NF[Formula: see text]P-NiCo2O4/NF electrode is constructed by employing P-NiCo2O4/NF as both the anode and cathode, it only requires a low 1.68[Formula: see text]V of cell voltage to reach the current density of 10[Formula: see text]mA cm[Formula: see text]. Notably, P-NiCo2O4/NF[Formula: see text]P-NiCo2O4/NF also exhibits excellent stability for over 30[Formula: see text]h-long. These results indicate that surface phosphation is an effective approach to improve the electrochemical performance of NiCo2O4/NF electrode materials.

Regulating the electronic configuration of ruthenium nanoparticles via coupling cobalt phosphide for hydrogen evolution in alkaline media

The strong adsorption of intermediates such as OH* and H* species on the surface of ruthenium (Ru) significantly impedes its electrocatalytic activity for hydrogen evolution reaction (HER) in alkaline media. Here, we propose the introduction of cobalt phosphide (CoP) to efficiently regulate the electronic configuration of Ru. The resultant CoP nanowire array decorated with ultrafine Ru nanoparticles on a conductive carbon cloth substrate (denoted as Ru–CoP/CC) displays comparable catalytic performance to the state-of-the-art Pt/C catalyst for HER in 1 M KOH solution, requiring an extremely low overpotential of only ~21 mV to achieve a current density of 10 mA cm−2, exhibiting a Tafel slope as low as ~49 mV/dec, and maintaining excellent stability over 24 h of electrolysis. Density functional theory calculations on the simulated charge distribution reveal that the regulation of the surface electronic structure of Ru by CoP decreases the adsorption energy of OH* and H* intermediates on the surface of Ru and ultimately contributes to the outstanding electrocatalytic activity of the Ru–CoP/CC electrode for HER.

Hybrid niobium and titanium nitride nanotube arrays implanted with nanosized amorphous rhenium–nickel: An advanced catalyst electrode for hydrogen evolution reactions

The scalable application of high-performance electrocatalysts with fine nanostructures for hydrogen evolution reactions (HER) depends on the development of durable and active electrode supports. Transition metal nitrides are considered as candidates due to their high conductivity, favorable catalytic activity, and excellent chemical stability in acidic or alkaline aqueous solutions. The present work proposed to fabricate self-ordered hybrid niobium–titanium (Nb–Ti) nitride nanotube arrays (NNAs) on Nb–Ti alloy panels by an anodization and subsequent nitridation process. Results showed that the highly ordered NNA is composed of mixed Nb4N5 and TiN and has merits of super hydrophilicity, outstanding corrosion resistance, and high conductivity. On the basis of the successful synthesis of Nb–Ti NNA, the nano–sized amorphous rhenium–nickel (Re–Ni) alloy was electrodeposited onto the NNA support, forming the Re–Ni/NNA composite electrode. Electrochemical tests exhibited that the Re–Ni/NNA composite electrode can provide a current density of 50 mA cm−2 in 1.0 M KOH at a potential of −0.18 V vs. RHE and maintain stability in a testing period of 100 h. This superior HER performance is attributed to the combination of Re–Ni particles and Nb–Ti NNA support, which can benefit the diminution of charge transfer resistance and the improvement of catalytic activity.

Electrochemical performance of porous Ni-alloy electrodes for hydrogen evolution reaction from seawater electrolysis.

The hydrogen evolution reaction in seawater is investigated using porous Ni–Cr–Fe, Ni–Fe–Mo, Ni–Fe–C and Ni–Ti electrodes, prepared by elemental powder reactive synthesis methods. The open porosity of the four kinds of electrode materials is 23.05%, 20.47%, 25.27%, and 29.05%, respectively. The electrochemical performance of the four kinds of electrodes has been researched by polarization measurement, cyclic voltammetry and electrochemical impedance spectroscopy. The preliminary results demonstrate that the porous Ni–Cr–Fe electrode has superior catalytic activity and relatively good long-term stability for hydrogen evolution reaction in seawater. The high efficiency and reasonable stability of the porous Ni–Cr–Fe electrode catalyst demonstrate its promising applications in the rising hydrogen revolution.

A robust self-stabilized electrode based on Al-based metallic glasses for a highly efficient hydrogen evolution reaction

Al-based metallic glass ribbon with a nanoporous layer of high-entropy alloy is a robust advanced self-stabilized free-standing electrode for hydrogen evolution reaction.

Self-supported Hierarchical Fe(PO3)2@Cu3P nanotube arrays for efficient hydrogen evolution in alkaline media

Developing high-efficient and Earth-abundant electrocatalysts toward hydrogen evolution reaction (HER) is strongly desired for electrochemical water splitting but remains a considerable challenge. Herein, we propose a 3D hierarchical Fe(PO3)2@Cu3P heterostructure nanotube arrays on Cu foams for promising HER catalysts. The HER performance can be tuned by changing FeCl3 concentrations and the optimized cathode exhibits excellent HER activity in 1 M KOH with a low overpotentials of 108 mV @ 10 mA cm−2 and a small Tafel slope of 84 mV dec−1. Furthermore, this electrode delivers high electrochemical durability with stable operation for 24 h. Such high performance can be ascribed to the unique hierarchical heterostructure with large electrochemical surface area, synergistic effect and fast electron transport. Our study can provide new inspiration for rational construction of copper-based hierarchical nanomaterials for HER electrodes and other energy-related applications.

Niobium-based semiconductor electrodes for hydrogen evolution reaction

This contribution focusses on the use of Nb-based materials for the preparation of hybrid nickel-semiconductor electrodes for use in the electrochemical generation of hydrogen. The Nb-based semiconductors (i.e., Nb2O5 and Nb3(PO4)5) show good performance for the H2 evolution reaction (HER) using a non-toxic electrolyte (K2CO3) under true water-splitting conditions. Particularly, Nb2O5 shows HER efficiency two orders of magnitude higher than its TiO2 counterparts. Tafel analysis suggests the HER mechanism is the same for all type of electrodes studied and electrochemical impedance spectroscopy indicates these hybrid Ni–Nb-semiconductor electrodes are sensitive to light exposure, unlike TiO2. We propose that the differences in impedance upon irradiation are due to the band structure of these hybrid electrodes, which have lower Schottky barrier heights and show smaller work function values.

Co-CoO/ZnFe2O4 encapsulated in carbon nanowires derived from MOFs as electrocatalysts for hydrogen evolution

Transition metals are increasingly attracting interest in electrocatalysts for use in water decomposition due to their excellent catalytic activity and stability. Simultaneously, metal-organic frameworks with designable metal ion centers and organic ligands are the promising precursors for the one-step synthesis of metal encapsulated in carbon composites for alkaline hydrogen evolution reaction (HER). Herein, we report the successful construction of Co-CoO/ZnFe2O4 encapsulated in carbon nanowires (Co-CoO/ZnFe2O4@CNWs) by annealing as-synthesized nanowire Co/Zn/Fe-MOF at 400 °C in N2. This structure provides the rich defect sites and active centers, and the synergy of Co, CoO and ZnFe2O4 lead to efficient hydrogen evolution when the composite is used as a catalytic electrode for HER in 1.0 M KOH. The catalyst shows a low initial overpotential (97 mV) and a small Tafel slope (138 mV dec−1), and the overpotential at 10 mA cm−2 is only 226 mV. In addition, this composite material exhibits excellent long-term durability even after 1000 cycles. It is expected that it is a potential alternative catalyst for rational utilization in the field of electrolytic water decomposition.

Hydrogen bubble evolution from magnetized nickel wire electrode

How to reduce the bubble coverage of the electrode is one of the key issues in water electrolysis which is related to the reduction of energy consumption. In this work, the magnetized nickel electrode with 100 μm diameter is used as working electrode in hydrogen evolution reaction (HER) during alkaline water electrolysis (1 mol/L, KOH). According to the experimental observation, both of the bubble's diameter and number have decreased at the magnetized surface compared with the unmagnetized one. The B–H loop measurement shows that the residual magnetic field intensity (Br) of the magnetized nickel electrode is up to 0.03 T. It can be found from the numerical simulation result that the residual magnetic field exactly right brings the Lorentz force and magnetohydrodynamic (MHD) convection near the electrode surface, which play the role of helping hydrogen bubble release from the electrode, even if the external magnetic field is absent in experiment. The new finding may develop a new way of utilizing magnetic field in water electrolysis for gas product elimination and energy conservation.

MoS2 microflowers with enriched active edges self-assembled on Ti mesh as a binder-free electrode for catalytic hydrogen evolution

In this work, a template-free hydrothermal strategy has been developed to fabricate 3D hierarchical MoS2 microflowers on macroporous Ti mesh (MoS2 MF-Ti) as a binder-free electrode for hydrogen evolution reaction (HER). It is found that the Ti mesh is able to provide an ideal platform for self-assembly of the MoS2 nanosheets into the hierarchical microflowers. The as-prepared MoS2 MF-Ti electrode is characteristic of meso/macro porous structures, abundant active edges and good conductivity. As a result, the MoS2 MF-Ti demonstrates greatly enhanced electrocatalytic activity and stability toward HER due to its desirable structural features.

Bimetal Networked Nanosheets CoxNi3−xS2 as An Efficient Electrocatalyst for Hydrogen Evolution

AbstractFor the first time, 3D networked CoxNi3−xS2 nanosheets were facilely grown on Ni foam via two‐step hydrothermal method forming a composite electrode (CoxNi3−xS2/NF) for electrocatalytic hydrogen evolution reaction (HER) under alkaline condition. With x value being 1.4, the as‐prepared Co1.4Ni1.6S2/NF shows superior performance as a HER electrode with low overpotentials of 68 mV, 160 mV and 226 mV at current densities of 10, 50 and 100 mA cm−2 respectively and exhibits remarkable electrochemical durability for 50 h in 1.0 M KOH solution. We propose that the synergistic and electron‐coupling effect between Co and Ni atoms in the CoxNi3−xS2/NF networked nanosheets lead to abundant active sites on surface and optimizes electronic structure. Density functional theory calculations indicate the introduction of Co atom can reduce the adsorption of H* thus optimize the hydrogen adsorption free energy. The CoxNi3−xS2 nanosheets not only break through the limitations of traditional Ni−Co−S materials at the ratio of Ni and Co : S as 3 : 4 but also improve the activity of hydrogen evolution. The 3D CoxNi3−xS2/NF nanomaterials become a promising alternative to the Pt‐based electrocatalysts for hydrogen evolution.

3D hierarchical nanostructured Ni–Co alloy electrodes on porous nickel for hydrogen evolution reaction

Nanostructured Ni–Co alloys decorated on 3D porous nickel electrodes for hydrogen evolution reaction (HER) are successfully prepared through a facile and effective electrodeposition method. By adjusting the current density of electrodeposition, Ni–Co alloys with different surface morphologies like nanocones, leaf-like structures and flakes can be obtained. The HER catalytic activity has been greatly reinforced with decorated Ni–Co alloys. Meanwhile, the HER performance of nanocone Ni–Co alloys outperforms that of leaf-like and flaky Ni–Co alloys. The nanocone Ni–Co alloys exhibit outstanding HER activity, only requiring an overpotential of 86.7 mV at 10 mA cm−2, along with a low Tafel slope of 69.8 mV dec−1 and 3.4 Ω charge transfer resistance. This nanocone electrode remains stable for 10 h of chronopotentiometric measurement. Such enhanced catalytic performance stems from the porosity and the high population of sharp edges, as well as surface oxidation/metallic states and synergistic effects between Ni and Co.

Screening of electrocatalysts for hydrogen evolution reaction using bipolar electrodes fabricated by composition gradient magnetron sputtering

This paper reports the facile fabrication of bipolar electrodes using composition gradient magnetron sputtering and subsequent activity screening of the prepared electrodes for hydrogen evolution reaction using bipolar electrochemistry. The electrocatalysts layers based on Ni–Mo, Au–Mo and Au–Ni alloys were deposited in form of compositional gradients on the bipolar electrodes. Concentration of the elements in the gradients varies from 40 to 60 at. % across the bipolar electrodes depending on the deposition conditions. The results of the screening experiments for the hydrogen evolution activity were also confirmed by conventional voltammetry measurements. We find that optimal compositions of the electrocatalyst for hydrogen evolution reaction are Au2Ni, AuMo2, Ni2Mo and Ni2Mo alloy has the highest catalytic activity. Mechanisms of HER on selected alloy compositions was also studied in more detail using voltammetry experiments.