Electrocatalytic Hydrogen Evolution Performance Research Articles

Nanoporous niobium nitride (Nb2N) with enhanced electrocatalytic performance for hydrogen evolution

Abstract The transition metal nitrides (TMNs) with nanoporous structure have shown great promise as potential electrocatalysts for the hydrogen evolution reaction (HER). Herein, self-organized nanoporous Nb 2 N was first successfully synthesized through the anodization of niobium in mixed oxalic acid/HF electrolyte, followed by a simple annealing treatment in the ammonia atmosphere. Due to the highly ordered nanoporous structure with abundant active sites and the enhanced electrical conductivity, the Nb 2 N exhibits a high catalytic current (326.3 mA cm −2 ) and low onset potential (96.3 mV), which is almost 3.9 times and 4.2 times better than that of Nb 2 O 5 , respectively. Meanwhile, the Nb 2 N also presents low Tafel slope (92 mV dec −1 ), and excellent cycling durability. More importantly, this study will provide more opportunities for designing and fabricating niobium compounds as an innovative HER catalysts.

Enhanced electrocatalytic hydrogen evolution performance of MoS2 ultrathin nanosheets via Sn doping

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have drawn much attention due to their unique physical and chemical properties. Molybdenum disulfide (MoS2) is particularly promising in hydrogen evolution reaction (HER) as a substitute for noble-metal catalysts. Although numerous attempts have been made to improve the HER activity of MoS2, engineering the MoS2-based electrocatalysts with activities similar to noble-metal catalysts remains challenging. Herein, we synthesize high-quality tin doped molybdenum disulfide (Sn-MoS2) ultrathin nanosheets by a g-C3N4 sacrificial template assisted thermolytic approach, and detailly investigate the role of Sn doping on the HER activity. The porous Sn-MoS2 nanosheets displays superior HER performance, exhibiting an overpotential of 28mV at 10mAcm−2 and a Tafel slope of 37.2mVdec−1 with an admirable stability. Compared to pristine MoS2 nanosheets, the significantly improved catalytic activity is ascribed to the increased active edge sites, enhanced intrinsic catalytic activity for each active site as well as accelerated electron transfer upon Sn doping. This work may provide guidelines for the design and synthesis of efficient non-precious HER catalysts.

An efficient porous molybdenum diselenide catalyst for electrochemical hydrogen generation

A simple approach to fabricate a vertically aligned porous MoSe2 by a two-step co-electrodeposition/etching method was proposed. The etching process induces MoSe2 porous 3D structure formation. The porous MoSe2 nanosheet exhibits a high electrocatalytic performance for hydrogen evolution.

One-pot hydrothermal synthesis and selective etching method of a porous MoSe2 sand rose-like structure for electrocatalytic hydrogen evolution reaction

A simple approach to fabricate a porous MoSe2 by a two-step-solvothermal/etching method was proposed. The etching process leads to a MoSe2 porous 3D structure formation with high electrocatalytic performance for hydrogen evolution.

On the photocatalytic and electrocatalytic hydrogen evolution performance of molybdenum sulfide supported on TiO2

This study aimed to define key preparation and treatment parameters determining the hydrogen evolution reaction (HER) performance of molybdenum sulfide-based photocatalysts. Amorphous and nanocrystalline molybdenum sulfide catalysts supported on titania have been studied in photocatalytic and electrochemical HER. The results of HER measurements were compated to the thiophene hydrodesulfurization HDS activity. Titania polymorph plays a crucial role for HER: high-surface area anatase PC500 and anatase-rutile Degussa P25 show high HER performance, whereas rutile nanorods demonstrate poor activity. Two preparation methods applying impregnation and solution deposition techniques have been compared. Solution deposition affords superior activity, with a maximum HER rate for 0.5%wt. Mo loading, even if the dispersion of MoS2 phase and HDS activity are better for impregnated systems. Therefore, for the photocatalytic performance not the dispersion of MoS2 and abundance of edge sites but efficient electron hopping from the semiconductor to the co-catalyst is most important. In order to study the influence of the MoS2 edges state, the solids reduced under H2 or treated in pure H2S were compared. The presence edge S22− groups have a positive influence on the photo- and electrocatalytic HER activity.

Porous nickel disulfide/reduced graphene oxide nanohybrids with improved electrocatalytic performance for hydrogen evolution

Single porous nickel disulfide (NiS2) nanoballs and nanohybrids of NiS2 with reduced graphene oxide (NiS2/rGO) were successfully prepared by a simple hydrothermal process in the absence or presence of graphene oxide. NiS2/rGO nanocomposites exhibit remarkable electrocatalytic performance for hydrogen evolution from water splitting due to the plentiful active sites in the porous NiS2, the improved conductivity and the positive synergetic effect between NiS2 and rGO. The nanocomposites displayed superior activity for the hydrogen evolution reaction (10mAcm−2 vs. −200mV, Tafel slope of 52mVdec−1) and an excellent electrocatalytic stability.

Electrodeposition mechanism and characterization of Ni–Mo alloy and its electrocatalytic performance for hydrogen evolution

In the study, the electrodeposition mechanism of Ni–Mo alloy was investigated. Potentiostatic deposition showed that the presence of MoO42− could reduce the deposition overpotential of Ni, and the deposition current efficiency of Ni–Mo alloy was lower than pure Ni deposition as the potential moved negatively. Cyclic Voltammetry (CV) indicated that both the first reduction peak for Ni deposition and the deposition peak of Ni–Mo alloy moved to more positive potentials as the content of Ni2+ increased, but the deposition peak of Ni–Mo alloy moved to more negative potentials as the content of MoO42− increased. The cathodic polarization curve on Rotating Disc Electrode (RDE) presented that Ni–Mo codeposition was controlled by charge transfer. The morphology, composition and structure of Ni–Mo alloy were characterized by SEM, EDS and XRD. The results showed the Ni–Mo alloy coatings exhibited a spherical and cauliflower-like pattern, having a considerably rougher surface, with nano-crystal structure when the elements composition was Ni80.14Mo19.59. The electrochemical activity for hydrogen evolution of Ni–Mo alloy was studied in 30 wt.% KOH at 25 °C using steady-state polarization and electrochemical impedance spectroscopy (EIS) methods. The results clearly demonstrated that an increase in the electrochemical activity for hydrogen evolution of the Ni–Mo alloy coating can be attributed both higher exchange current density and larger real electrode area.

Hierarchical Transition-Metal Dichalcogenide Nanosheets for Enhanced Electrocatalytic Hydrogen Evolution.

Hierarchical transition-metal dichalcogenide nanosheets are constructed through a versatile strategy, where the thermal polymerization of melamine and subsequent decomposition of carbon nitride successively guide the horizontal and vertical growths of transition-metal chalcogenides. Abundant edges and high surface areas endow the hierarchical MoS2 and WS2 nanosheets with excellent electrocatalytic performance for hydrogen evolution, including low onset potentials and high current densities.

Comparison of the Performance of CoP-Coated and Pt-Coated Radial Junction n(+)p-Silicon Microwire-Array Photocathodes for the Sunlight-Driven Reduction of Water to H2(g).

The electrocatalytic performance for hydrogen evolution has been evaluated for radial-junction n(+)p-Si microwire (MW) arrays with Pt or cobalt phosphide, CoP, nanoparticulate catalysts in contact with 0.50 M H2SO4(aq). The CoP-coated (2.0 mg cm(-2)) n(+)p-Si MW photocathodes were stable for over 12 h of continuous operation and produced an open-circuit photovoltage (Voc) of 0.48 V, a light-limited photocurrent density (Jph) of 17 mA cm(-2), a fill factor (ff) of 0.24, and an ideal regenerative cell efficiency (ηIRC) of 1.9% under simulated 1 Sun illumination. Pt-coated (0.5 mg cm(-2)) n(+)p-Si MW-array photocathodes produced Voc = 0.44 V, Jph = 14 mA cm(-2), ff = 0.46, and η = 2.9% under identical conditions. Thus, the MW geometry allows the fabrication of photocathodes entirely comprised of earth-abundant materials that exhibit performance comparable to that of devices that contain Pt.

Electroless Ni–W–Cr–P alloy coating with improved electrocatalytic hydrogen evolution performance

The quaternary Ni–W–Cr–P alloy coatings were deposited on copper alloy by an electroless deposition process. Micromorphology, microstructure and hydrogen evolution reaction (HER) activity of electroless Ni–W–Cr–P coatings were examined. X-ray diffraction analysis showed that the Ni–W–Cr–P coatings were solid solution, and crystallisation started to occur with increasing heat treatment temperature. The experimental results also revealed that HER activity of the Ni–W–Cr–P coatings was enhanced compared with those of the uncoated. Moreover, with increasing annealing temperature, HER activity of the Ni–W–Cr–P coatings varied slightly. When heated at 500°C, the electrode got the best Tafel slope of 144 mV/decade and quite small overpotentials of 354 and 479 mV at the current densities of 10 and 30 mA cm−2 respectively. Electroless deposition is a good way to get alloy coating, which can improve the electrocatalytic activity of the hydrogen generation efficiently.

Synthesis and electrocatalytic hydrogen evolution performance of Ni–Mo–Cu alloy coating electrode

Ni–Mo–Cu alloy coating electrode was prepared on copper substrate by constant current electrodeposition and characterized by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The electrochemical characterization for hydrogen evolution reaction (HER) was investigated by cyclic voltammetry (CV) curves, linear sweep voltammetry (LSV) curves and electrochemical impedance spectroscopy (EIS) techniques. Parameters affecting the electrocatalytic activity for the HER are systematically investigated. Results show the Ni–Mo–Cu coating by the introduction of Cu has a rough and cauliflower-like structure and presents a most efficient activity for HER in comparison with binary Ni–Mo electrode. Its remarkably enhanced catalytic activity is attributed to the high surface area as well as synergistic interaction between Ni, Mo and Cu.

MoS2 nanosheet/Mo2C-embedded N-doped carbon nanotubes: synthesis and electrocatalytic hydrogen evolution performance

Ultrathin MoS2 nanosheets were grown on Mo2C-embedded N-doped carbon nanotubes through in situ solid and subsequent hydrothermal reactions, showing excellent electrocatalytic activity for hydrogen evolution.

Electrochemical Preparation of Ni-Sn Active Cathode and Its Electrocatalytic Hydrogen Evolution Reaction Mechanisms in Alkaline Solution

A simple galvanostatic electrodeposition method was used to synthesize an active Ni-Sn electrode on a Cu foil substrate. Characterization by high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) revealed that the crystal structures of the deposited films transformed from amorphous structures composed of Ni crystal embryos and amorphous Ni-Sn to Ni3Sn4/Ni3Sn2 mixed crystals with increasing Sn content. Scanning electron microscope (SEM) images indicated that the amorphous Ni-Sn electrode possessed a smooth surface with uniform distribution of small particles, whereas the Ni3Sn4/Ni3Sn2 mixed crystalline electrode exhibited a rough surface composed of lamellar structures. The polarization curves measured in 1 mol·L-1 NaOH solution at 25 °C indicated that the amorphous Ni-Sn electrode showed a smaller overpotential (85 mV) and better electrocatalytic performance for hydrogen evolution than the mixed crystalline electrode. Electrochemical impedance spectroscopy (EIS) results showed that the hydrogen evolution reaction occurs 1479 Acta Phys. ⁃Chim. Sin. 2013 Vol.29 on the Ni-Sn alloy electrode under a mixture of Volmer and Heyrovsky control. The higher activity of the amorphous Ni-Sn electrode was attributed to the faster charge transfer and electrochemical adsorption and desorption rates of hydrogen atoms compared with those on the mixed crystalline electrode.