Stable Electrocatalyst For Hydrogen Evolution Research Articles

Hierarchical Design of Homologous NiCoP/NF from Layered Double Hydroxides as a Long-Term Stable Electrocatalyst for Hydrogen Evolution

Ternary transition metal phosphides (TTMPs) with two-dimensional heterointerface and adjustable electronic structures have been widely studied in hydrogen evolution reactions (HER). However, single-phase TMPs often have inappropriate H* adsorption energy and electronic transfer efficiency in HER. Herein, we utilized the heterogeneity in the crystal structure to design an efficient and stable catalyst from the NiCoP nanowire@NiCoP nanosheet on nickel foam (NW-NiCoP@NS-NiCoP/NF) for HER. Layered double hydroxides (LDHs) with a heterogeneous matrix on crystal surfaces were grown under different reaction conditions, and non-metallic P was introduced by anion exchange to adjust the electronic structure of the transition metals. The hierarchical structure of homologous NiCoP/NF from the LDH allows for a larger surface area, which results in more active sites and improved gas diffusion. The optimized NW-NiCoP@NS-NiCoP/NF electrode exhibits excellent HER activity, with an overpotential of 144 mV, a Tafel slope of 84.2 mV dec−1 at a current density of 100 mA cm−2 and remarkable stability for more than 500 h in 1.0 M KOH electrolyte. This work provides ideas for elucidating the rational design of structural heterogeneity as an efficient electrocatalyst and the in situ construction of hierarchical structures.

Highly efficient and stable electrocatalyst for hydrogen evolution by molybdenum doped Ni-Co phosphide nanoneedles at high current density

Highly efficient and stable electrocatalyst for hydrogen evolution by molybdenum doped Ni-Co phosphide nanoneedles at high current density

Facile in-situ fabrication of nanocoral-like bimetallic Co-Mo carbide/nitrogen-doped carbon: a highly active and stable electrocatalyst for hydrogen evolution

It is vital to exploit non-noble metal catalysts with ample natural reserve and high performance for reducing energy consumption during electrocatalytic water splitting process. Herein, nanocoral-like bimetallic Co-Mo carbide/nitrogen-doped carbon (Co-Mo2C/N-C) electrocatalysts have been successfully prepared by high temperature pyrolysis of CoMoO4 and melamine for hydrogen evolution reaction (HER). When the mass ratio of CoMoO4 and melamine is 1:15, nanocoral-like Co-Mo2C/N-C electrocatalyst shows optimal electrocatalytic HER activity, which just needs overpotentials of only 212 and 290 mV at the current density of 10 and 40 mA cm−2, respectively. Besides, it shows low charge transfer resistance and surpassing stability for uninterrupted HER in 1.0 M KOH electrolyte. The eximious electrochemical performance of Co-Mo2C/N-C is put down to the fact that N-C can effectively disperse Co-Mo2C nanoparticles. The results suggest that nanocoral-like Co-Mo2C/N-C with considerable catalytic activity and superior durability is believed as promising candidate to substitute noble metal catalysts for green and renewable hydrogen production by electrocatalytic water splitting.

Metal organic framework derived Ni0.15Co0.85S2@MoS2 heterostructure as an efficient and stable electrocatalyst for hydrogen evolution

Molybdenum Sulfide (MoS2) represents an excellent performance non precious electrocatalyst for hydrogen evolution reaction (HER). There are some challenges to further improve the HER property of MoS2 owing to its inferior conductivity, serious aggregation and limited active sites. In this study, Ni0.15Co0.85S2@MoS2 hybrids are successfully synthesized in a simple hydrothermal method, where Ni-Co Metal Organic Frameworks (NiCo-MOFs) are served as precursors, which hydrothermally react with ammonium molybdate tetrahydrate (H24Mo7N6O24·4H2O) and thiourea (CH4N2S) to obtain a catalyst for HER. As expected, the optimized Ni0.15Co0.85S2@MoS2 catalyst presents ultrahigh HER property, a low overpotential of 79 mV at 10 mA cm−2 and a Tafel slope of 52 mV dec−1 can be observed in 1.0 M KOH, accompanied by excellent stability. This result displayed in our study could give a new strategy for designing and synthesizing more economical electrocatalysts based on MOFs as precursors in the future.

Design of MoS2/Graphene van der Waals Heterostructure as Highly Efficient and Stable Electrocatalyst for Hydrogen Evolution in Acidic and Alkaline Media

The thermodynamically stable phase of molybdenum disulfide (MoS2) is evaluated as a promising and durable nonprecious-metal electrocatalyst toward the hydrogen evolution reaction (HER); however, its actual catalytic activity is restricted by an inert basal plane, low electronic conductivity, low density, and using efficiency of edged atoms. Moreover, 2D/2D van der Waals (vdws) heterostructures (HSs) with face-to-face contact can construct a highly coupled interface and are demonstrated to have immense potential for catalytic applications. In the present work, a 2D/2D hetero-layered architecture of an electrocatalyst, based on the alternate arrangement of ultrasmall monolayer MoS2 nanosheets (approximately 5-10 nm) and ultrathin graphene (G) sheets, is prepared by a facilely chemical process, which is named as MoS2/G HS. The unique structural characteristic of MoS2/G HS is in favor of accommodating more active sites as the centers of ad/desorption hydrogen and transferring and separating the charges at a coupled interface to improve the electronic conductivity and durability. The density functional theory calculation results further confirm that the alternately arranged G layers and MoS2 monolayers, as well as the expanded interplanar distance of 1.104 nm for MoS2/G HS, can exhibit a superior HER performance in both 0.5 M H2SO4 and 1.0 M KOH.

W2C nanodot-decorated CNT networks as a highly efficient and stable electrocatalyst for hydrogen evolution in acidic and alkaline media.

Although tungsten carbide (W2C) has long been reported as an excellent platinum-like catalyst, it is still a challenge to synthesize W2C as an electrocatalyst for a highly efficient hydrogen evolution reaction (HER) due to its high onset overpotential, inevitable aggregation, and lack of a scalable and controllable synthesis method. Herein, we synthesized W2C nanodot-decorated CNT networks (W2C@CNT-S) via a facile and scalable spray drying method followed by a carbonization process. It is demonstrated that this unique nanoarchitecture, constructed by ultrafine W2C nanodots homogeneously decorated on a three-dimensional and conductive CNT skeleton, leads to the exposure of abundant catalytic sites and promotes highly efficient electron transfer and ion diffusion during the HER process. As a result, in acidic and alkaline media, the optimized W2C@CNT-S hybrid exhibited excellent HER performance with very low onset overpotentials of only 60 and 40 mV (vs. RHE) and very small Tafel slopes of 57.4 and 56.2 mV dec-1, and only needed 176 and 148 mV (vs. RHE) to obtain a current density of 10 mA cm-2, respectively; it also showed outstanding long-term durability even after a 30-hour test in both acidic and alkaline media. This study presents an overview of a low-cost and scalable spray-drying strategy to synthesize a high-performance carbide-based electrocatalyst for hydrogen evolution.

Hierarchical MoSe2-CoSe2 nanotubes anchored on graphene nanosheets: A highly efficient and stable electrocatalyst for hydrogen evolution in alkaline medium

Hierarchical MoSe2-CoSe2 nanotubes anchored on graphene nanosheets (G/MS-CS NTs) are in-situ converted from the CoMoO4 nanowires (NWs) and graphene oxide hybrid precursor via a facile hydrothermal method. As an electrocatalyst, G/MS-CS NTs show highly efficient and stable performance for hydrogen evolution reaction (HER) in alkaline medium. G/MS-CS NTs demonstrate superior HER performance with a very low onset overpotential of 109 mV vs. RHE, a low overpotential of 198 mV vs. RHE at −10 mA cm−2, a small Tafel slope of 79 mV dec−1, a large current density of 53.7 mA cm−2 at −300 mV vs. RHE, and excellent long-term cycling stability. The outstanding HER activity of G/MS-CS NTs is attributed to its unique hierarchical structure with MS-CS NTs anchored on two-dimensional graphene nanosheets. The MS-CS NTs are well-constructed by few-layered MoSe2 nanosheets and CoSe2 nanoparticles with highly homogenous distribution, which can not only effectively suppress the aggregation of MoSe2 nanosheets, but also generate more active sites or edges to enhance the electrocatalytic activity. In addition, the highly conductive graphene matrix can efficiently promote the electron transfer from the electrode to the active sites on MS-CS NTs during electrocatalytic process, further improving the HER performance.

Holey Ni-Cu phosphide nanosheets as a highly efficient and stable electrocatalyst for hydrogen evolution

Hydrogen, generated by electrocatalytic process, is one of the most promising sources of green and sustainable energy. Herein, we report a novel elctrocatalyst for hydrogen evolution reaction (HER) fabricated by doping Ni foam (NF) supported Ni2P nanosheets with Cu atoms. The Cu atoms effectively tune the structure and physicochemical properties of Ni2P, leading to the lower HER free energy, improved electrical conductivity, and high exposure of surface active sites. The optimized Ni1.8Cu0.2-P displays an excellent catalytic performance and stability, which is demonstrated by the low overpotentials of 78 (Tafel slope: 70 mV dec-1) and 245 mV to reach a current density of 10 and 100 mA cm-2 for the HER in 1.0 M KOH. The high electrocatalytic activity of Ni1.8Cu0.2-P is attributed to the increased Fermi level and the exposed active crystal plane (201). The H2 amount produced with a current density of 10 mA cm-2 is about 1.91 mmol h-1 cm-2, which is the highest value among the reported non-precious metal catalysts.

Ruthenium ion containing N and S rich triazine based metallopolymer as a low overpotential acid stable electrocatalyst for hydrogen evolution

The rational design of under saturated redox-active metal centers distributed on the organo-polymeric surfaces has gained substantial attention in electrocatalysis. Herein, we report the ruthenium ions containing triazine-trithiolate (M-C3N3S3) metallopolymers chemically coordinated to the copper substrate as a stable, low overpotential electrocatalyst for H2 evolution in strong acidic media. The XPS analyses confirm the presence of Ru4+/Ru3+ and Cu2+/Cu1+ in the metallopolymers. XPS and FTIR spectral analysis suggest the presence of disulphide linkages. A significant overpotential reduction for hydrogen evolution is observed with CuRu-C3N3S3 metallopolymer of just ∼−145 to −155 mV vs RHE to attain −10 mA cm−2 in 0.5 M H2SO4. The high exchange current densities and double layer capacitance could be attributed to the protonation capacity of redox-active centers and the uncoordinated ligand centers (N and S). The concerted proton-electron transfer mechanism improves the H2 evolution. These metallopolymers show a low onset hydrogen evolution potential of just −45 mV vs RHE (i = −1 mA cm−2). Tafel slope values suggest the Volmer-Heyrovsky mechanism is involved in HER. The potentiostatic impedance spectral analyses indicate, CuRuTCA show the reduction in charge transfer resistance of nearly 10 and 700 times with respect to CuNiTCA and bare Cu electrodes respectively. These electrodes display an excellent long-term stability for hydrogen evolution.

Few-layered WSe2 nanoflowers anchored on graphene nanosheets: a highly efficient and stable electrocatalyst for hydrogen evolution

Tungsten selenide (WSe2) has emerged as a promising electrocatalyst for hydrogen evolution reaction (HER), and its HER performance strongly depends on its conductivity and exposed edge sites. Herein, a RGO/WSe2 hybrid network constructed with few-layered WSe2 nanoflowers anchored on graphene nanosheets has been synthesized through a facile one-pot solvothermal method. Compared with bare WSe2 nanoflowers with relatively poor HER performance, the RGO/WSe2 hybrid demonstrates a highly effective and stable electrocatalytic performance: it delivers a small Tafel slope of 57.6mVdec−1, a remarkably low onset potential of∼150mV, a high current density of 38.43mAcm−2 at 300mV vs RHE and excellent long-term stability. The superior HER performance of RGO/WSe2 hybrid is attributed to the unique WSe2-anchored-on-graphene structure, which ensures the robust contact between the few-layered WSe2-nanoflowers catalyst and the highly conductive graphene matrix, leading to enhance the charge transfer kinetics between the catalytic edge sites and the graphene nanosheets. Therefore, the RGO/WSe2 hybrid is promising as high-performance catalysts for hydrogen evolution applications.

Interwoven WSe2/CNTs hybrid network: A highly efficient and stable electrocatalyst for hydrogen evolution

A WSe2/CNTs hybrid network (WCHN) composed of a few layers of WSe2 nanosheets interwoven with carbon nanotubes (CNTs) has been synthesized through a facile one-pot solvothermal method. The WCHN is shown to be a highly effective and stable electrocatalyst for hydrogen evolution. Compared with bare WSe2, which has relatively poor performance for the hydrogen evolution reaction (HER), the WCHN exhibits superior HER performance with a small Tafel slope of 59.7mV/decade, a remarkably low onset potential of ~120mV, a high current density and excellent long-term stability. The significant enhancement in HER performance of the WCHN is attributed to the unique network structure produced by two-dimensional WSe2 nanosheets interwoven with one-dimensional highly conductive CNTs, which not only provides abundant active reaction sites, but also guarantees robust contact between the WSe2 nanosheets and the CNTs.

Synergetic effect of CoNPs and graphene as cocatalysts for enhanced electrocatalytic hydrogen evolution activity of MoS2

Highly active and stable electrocatalyst for hydrogen evolution have been developed on the basis of molybdenum sulfide on CoNPs–graphene hybrid support via a modified hydrothermal method.

Carbon-coated hollow mesoporous FeP microcubes: an efficient and stable electrocatalyst for hydrogen evolution

Carbon coated hollow mesoporous FeP microcubes derived from Prussian blue were superior in catalytic activity and durability toward electrochemical hydrogen evolution with an overpotential of 115 mV to drive 10 mA cm−2.

High-Performance Hydrogen Evolution from MoS2(1-x) P(x) Solid Solution.

A MoS2(1-x) P(x) solid solution (x = 0 to 1) is formed by thermally annealing mixtures of MoS2 and red phosphorus. The effective and stable electrocatalyst for hydrogen evolution in acidic solution holds promise for replacing scarce and expensive platinum that is used in present catalyst systems. The high performance originates from the increased surface area and roughness of the solid solution.

Highly active and stable hydrogen evolution electrocatalysts based on molybdenum compounds on carbon nanotube-graphene hybrid support.

Highly active and stable electrocatalysts for hydrogen evolution have been developed on the basis of molybdenum compounds (Mo2C, Mo2N, and MoS2) on carbon nanotube (CNT)-graphene hybrid support via a modified urea-glass route. By a simple modification of synthetic variables, the final phases are easily controlled from carbide, nitride to sulfide with homogeneous dispersion of nanocrystals on the CNT-graphene support. Among the prepared catalysts, Mo2C/CNT-graphene shows the highest activity for hydrogen evolution reaction with a small onset overpotential of 62 mV and Tafel slope of 58 mV/dec as well as an excellent stability in acid media. Such enhanced catalytic activity may originate from its low hydrogen binding energy and high conductivity. Moreover, the CNT-graphene hybrid support plays crucial roles to enhance the activity of molybdenum compounds by alleviating aggregation of the nanocrystals, providing a large area to contact with electrolyte, and facilitating the electron transfer.

MoS2 Formed on Mesoporous Graphene as a Highly Active Catalyst for Hydrogen Evolution

AbstractA highly active and stable electrocatalyst for hydrogen evolution is developed based on the in situ formation of MoS2 nanoparticles on mesoporous graphene foams (MoS2/MGF). Taking advantage of its high specific surface area and its interconnected conductive graphene skeleton, MGF provides a favorable microenvironment for the growth of highly dispersed MoS2 nanoparticles while allowing rapid charge transfer kinetics. The MoS2/MGF nanocomposites exhibit an excellent electrocatalytic activity for the hydrogen evolution reaction with a low overpotential and substantial apparent current densities. Such enhanced catalytic activity stems from the abundance of catalytic edge sites, the increase of electrochemically accessible surface area and the unique synergic effects between the MGF support and active catalyst. The electrode reactions are characterized by electrochemical impedance spectroscopy. A Tafel slope of ≈42 mV per decade is measured for a MoS2/MGF modified electrode, suggesting the Volmer‐Heyrovsky mechanism of hydrogen evolution.