Enhanced Hydrogen Evolution Reaction Activity Research Articles

Interface confined hydrogen evolution reaction in zero valent metal nanoparticles-intercalated molybdenum disulfide

Interface confined reactions, which can modulate the bonding of reactants with catalytic centres and influence the rate of the mass transport from bulk solution, have emerged as a viable strategy for achieving highly stable and selective catalysis. Here we demonstrate that 1T′-enriched lithiated molybdenum disulfide is a highly powerful reducing agent, which can be exploited for the in-situ reduction of metal ions within the inner planes of lithiated molybdenum disulfide to form a zero valent metal-intercalated molybdenum disulfide. The confinement of platinum nanoparticles within the molybdenum disulfide layered structure leads to enhanced hydrogen evolution reaction activity and stability compared to catalysts dispersed on carbon support. In particular, the inner platinum surface is accessible to charged species like proton and metal ions, while blocking poisoning by larger sized pollutants or neutral molecules. This points a way forward for using bulk intercalated compounds for energy related applications.

Light Auxiliary Hydrogen-Evolution Catalyst Based on Uniformly Pt Nanoparticles Decorated Molybdenum Sulfide Hybrids

The electrocatalytic splitting of water via hydrogen evolution reaction (HER) is one of the most efficient technologies for hydrogen production, while the massive consumption of precious Pt-based catalysts hinders its commercialization, bringing an urgent task to explore low-cost and earth-abundant alternatives. Herein, a cost-efficient system composed of metal Pt/molybdenum disulphide (MoS2) nanosheets hybrids for the HER by auxiliary of solar light is reported. The uniformly Pt nanoparticle decorated MoS2 sheets can be easily obtained under hydrothermal condition using oleylamine as capping agent and N,N-dimethylmethanamide (DMF) as intercalation molecule for MoS2 exfoliation. The Pt/MoS2 hybrid shows a significantly enhanced HER activity compared with bare MoS2 due to enhancing conductivity and reducing overpotential by electron transport between Pt and MoS2. As a result, a Tafel slope of 38 mV per decade is obtained, suggesting a highly efficient Volmer–Heyrovsky reaction of hydrogen evolution.

In situ cathodic activation of V-incorporated NixSy nanowires for enhanced hydrogen evolution.

In situ cathodic activation (ISCA) of V-incorporated NixSy nanowires supported on nickel foam (VS/NixSy/NF) can be realized in an alkaline hydrogen evolution reaction (HER) process, which provides not only clearly enhanced activity but also ultrahigh stability for HER. The ISCA process is continuous linear sweep voltammetry (LSV) on VS/NixSy/NF as a cathodic electrode with gradually enhanced HER activity. The activated VS/NixSy/NF (A-VS/NixSy/NF) demonstrates enhanced HER activity with an overpotential of 125 mV to drive 10 mA cm-2, which is much lower than that of other samples. It may be predicted that the ISCA-derived amorphous VOOH film covering on A-VS/NixSy/NF accelerates the HER process, and NiOOH may protect active sites from decaying, leading to excellent activity and structural stability. However, for single metal sulfides, the ISCA process of nickel or vanadium sulfides is not available, implying that the synergistic effect between Ni and V of VS/NixSy/NF may be the key to drive ISCA in alkaline HER. In addition, its ultra-high stability confirms that the stable active sites and nanostructures of A-VS/NixSy/NF are derived from ISCA. Therefore, the ISCA of V-incorporated transition metal sulfides in the alkaline HER process may be a facile and promising method to obtain efficient electrocatalysts.

Pt/C/Ni(OH)2 Bi-Functional Electrocatalyst for Enhanced Hydrogen Evolution Reaction Activity under Alkaline Conditions

The kinetics of hydrogen evolution and hydrogen oxidation reactions (HER/HOR) in alkaline electrolyte on Pt/C and a Pt/C/Ni(OH)2 bi-functional electrocatalyst were studied. The objective was to investigate the enhancement of hydrogen evolution activity of Pt in alkaline environments in presence of transition metal hydroxides, and to determine the optimum concentration of Ni(OH)2 to be added to maximize catalytic activity. The catalysts were prepared by mixing colloidal dispersions of nanosized Ni(OH)2 with a commercially-sourced Pt/C catalyst dispersed in water. Rotating disk electrode (RDE) measurements were performed in 0.1 M KOH at temperatures ranging from 273.15 K to 303.15 K, and the HOR/HER kinetic currents, obtained after IR and mass transport corrections, were fitted using the Butler-Volmer equation to estimate the exchange current densities at each temperature. Arrhenius plots showed very similar activation energies for Pt/C (35 ± 6 kJ/mol) and the bi-functional catalysts (38 ± 6 kJ/mol) –Pt/C/X%Ni(OH)2. The maximum exchange current density (2.44 ± 0.07 mA cm−2Pt at 303.15 K) was obtained with the catalyst containing 10 wt% Ni(OH)2, and was 2.4 times higher than for Pt/C (1.03 ± 0.07 mA cm−2Pt at 303.15 K). The bi-functional catalysts were evaluated in a hydroxide-exchange membrane water electrolyzer operated with ultrapure water, and outperformed Pt/C by about 0.15 V across the entire current density range.

Pt/RuO2-TiO2 Electrocatalysts Exhibit Excellent Hydrogen Evolution Activity in Alkaline Media

Alkaline water electrolysis is hindered by the slow kinetics of the hydrogen evolution reaction (HER) in alkaline media. We report enhanced HER activity of Pt on a mixed-metal-oxide support composed of titanium dioxide (TiO2) and ruthenium dioxide (RuO2). The Pt/RuO2-TiO2 (Pt/RTO) electrocatalyst was characterized by XRD, TEM and BET. The particle size of Pt was 6 ± 0.63 nm and the support surface area was 33 ± 1.15 m2/g. The activity of Pt/RTO toward HER and the hydrogen oxidation reaction (HOR) in 0.1 M KOH was compared against a benchmark Pt/C catalyst (46.5%Pt; Tanaka, K. K.) using the rotating disk electrode (RDE) technique. Pt/RTO outperformed the benchmark Pt/C over the range of temperatures studied (275–313 K). The exchange current density for Pt/RTO was 2.31 ± 0.06 mA/cm2Pt (at 295 K, 1600 rpm, in H2-saturated 0.1 M KOH), which was more than five times the measured exchange current density of the Pt/C benchmark under the same conditions. Pt/RTO and Pt/C were further evaluated in a solid-state alkaline water electrolyzer operated with ultrapure water. MEAs fabricated with Pt/RTO as the cathode and IrO2 as anode catalyst showed a 100–200 mV reduction in the cell voltage across the entire current density range, when compared to MEAs fabricated with Pt/C at the cathode and IrO2 at the anode.

Mn Doping of CoP Nanosheets Array: An Efficient Electrocatalyst for Hydrogen Evolution Reaction with Enhanced Activity at All pH Values

Heteratom doping is a possible way to tune the hydrogen evolution reaction (HER) catalytic capability of electrocatalysts. In this work, we report the development of Mn-doped CoP (Mn–Co–P) nanosheets array on Ti mesh (Mn–Co–P/Ti) as an efficient 3D HER electrocatalyst with good stability at all pH values. Electrochemical tests demonstrate that Mn doping leads to enhanced catalytic activity of CoP. In 0.5 M H2SO4, this Mn–Co–P/Ti catalyst drives 10 mA cm–2 at an overpotential of 49 mV, which is 32 mV less than that for CoP/Ti. To achieve the same current density, it demands overpotentials of 76 and 86 mV in 1.0 M KOH and phosphate-buffered saline, respectively. The enhanced HER activity for Mn–Co–P can be attributed to its more thermo-neutral hydrogen adsorption free energy than CoP, which is supported by density functional theory calculations.

Novel CoxSy/WS2 nanosheets supported on carbon cloth as efficient electrocatalyst for hydrogen evolution reaction

To maximum the activity of transition metal sulfides for hydrogen evolution reaction (HER), two strategies usually have been adopted including designing unique nanostructures and integrating other metal element. Herein, CoxSy/WS2 nanosheets supported on carbon cloth (CoxSy/WS2/CC) have been fabricated via a facile hydrothermal process. The cross-linked structures composed of CoxSy/WS2 nanosheets uniformly cover on the surface of CC, which may expose abundant active sites for HER and accelerate charge transfer rate. The molar ratio of CoxSy-incorporating has been investigated in detail. The molar ratio of W/Co = 1/3 (noted as CoxSy/WS2/CC-3) has been proved to have unique spherical CoxSy/WS2 nanostructure, which may further expose more active sites for HER. Electrochemical measurements demonstrate that CoxSy-incorporating can enhance HER activity and conductivity compared with WS2/CC. In addition, CoxSy/WS2/CC-3 exhibits the best HER activity, smallest charge transfer resistance and excellent stability than the counterparts, implying that the degree of CoxSy-incorporating may impact the HER activity of WS2. The mechanisms of CoxSy-incorporating on enhancing HER activity of WS2 have been discussed. It may offer a promising way to design transition metal sulfides-based electrocatalysts for HER by non-precious metal incorporating.

Three-dimensional N-doped, plasma-etched graphene: Highly active metal-free catalyst for hydrogen evolution reaction

Exploring highly active, durable and low-cost catalysts toward hydrogen evolution reaction (HER) holds a key to clean energy technologies. Heteroatoms-doped graphene-based materials are emerging as the most promising metal-free HER catalysts, but their catalytic activity remains largely unexplored. Herein, by rationally engineering the macroscopic architecture of graphene and its chemical/defective structures, we developed a three-dimensional (3D), N-doped, plasma-etched graphene (3DNG-P) as a highly active metal-free HER catalyst. The obtained 3DNG-P combined the merits of freestanding 3D porous architecture, high-level N-doping and plasma-induced enriched defects, resulting in a highly enhanced HER activity with a low overpotential of 128mV at 10mAcm−2 in acidic medium. Furthermore, the 3DNG-P displayed a favorable HER activity and stability over a wide pH range. The present study thus provides a new methodology for the design of graphene-based metal-free catalysts with high HER performance.

Plasma-etched, S-doped graphene for effective hydrogen evolution reaction

Heteroatom-doped graphene as highly efficient metal-free electrocatalyst is emerging as the most promising alternative to Pt-based electrocatalysts for hydrogen evolution reaction (HER). However, developing heteroatom-doped graphene with competitive HER activity remains a great challenge. Here, we reported an effective strategy to employ plasma-etching method to create more topological defects on S-doped graphene, and obtained plasma-etched, S-doped graphene exhibited a significantly enhanced HER activity with an overpotential of 178 mV at a current density of 10 mA cm−2. It was proved that the synergetic coupling between S-doping and plasma-induced topological defects contributed to the excellent HER performance. We further showed that the combination of high S-doping level with thiophene-S-rich species and appropriate amount of topological defects could maximize the HER activity. The successful combination of plasma-assisted defect engineering and heteroatom-doping in this work may open up a new pathway for developing highly efficient graphene-based metal-free catalysts toward HER.

Phase and Interface Engineering of Platinum-Nickel Nanowires for Efficient Electrochemical Hydrogen Evolution.

The design of high-performance electrocatalysts for the alkaline hydrogen evolution reaction (HER) is highly desirable for the development of alkaline water electrolysis. Phase- and interface-engineered platinum-nickel nanowires (Pt-Ni NWs) are highly efficient electrocatalysts for alkaline HER. The phase and interface engineering is achieved by simply annealing the pristine Pt-Ni NWs under a controlled atmosphere. Impressively, the newly generated nanomaterials exhibit superior activity for the alkaline HER, outperforming the pristine Pt-Ni NWs and commercial Pt/C, and also represent the best alkaline HER catalysts to date. The enhanced HER activities are attributed to the superior phase and interface structures in the engineered Pt-Ni NWs.

Phase and Interface Engineering of Platinum–Nickel Nanowires for Efficient Electrochemical Hydrogen Evolution

AbstractThe design of high‐performance electrocatalysts for the alkaline hydrogen evolution reaction (HER) is highly desirable for the development of alkaline water electrolysis. Phase‐ and interface‐engineered platinum–nickel nanowires (Pt‐Ni NWs) are highly efficient electrocatalysts for alkaline HER. The phase and interface engineering is achieved by simply annealing the pristine Pt‐Ni NWs under a controlled atmosphere. Impressively, the newly generated nanomaterials exhibit superior activity for the alkaline HER, outperforming the pristine Pt‐Ni NWs and commercial Pt/C, and also represent the best alkaline HER catalysts to date. The enhanced HER activities are attributed to the superior phase and interface structures in the engineered Pt‐Ni NWs.

A Perovskite Electrocatalyst for Efficient Hydrogen Evolution Reaction.

Perovskite oxides are demonstrated for the first time as efficient electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solutions. A-site praseodymium-doped Pr0.5 (Ba0.5 Sr0.5 )0.5 Co0.8 Fe0.2 O3- δ (Pr0.5BSCF) exhibits dramatically enhanced HER activity and stability compared to Ba0.5 Sr0.5 Co0.8 Fe0.2 O3- δ (BSCF), superior to many well-developed bulk/nanosized nonprecious electrocatalysts. The improved HER performance originates from the modified surface electronic structures and properties of Pr0.5BSCF induced by the Pr-doping.

One-pot synthesis of hierarchical Ni2P/MoS2 hybrid electrocatalysts with enhanced activity for hydrogen evolution reaction

A simple one-pot synthesis method has been used to fabricate novel Ni2P/MoS2 hybrid electrocatalysts for hydrogen evolution reaction (HER). Owing to the weak conductivity and layered structure of MoS2, Ni2P nanoparticles with excellent conductivity and activity have been doped into MoS2 for improving the electrocatalytic performances for HER. The structure and morphology of the as-prepared Ni2P/MoS2 hybrid nanostructures are characterized. XRD and XPS show the elemental composition and valence of Ni2P/MoS2. SEM and TEM confirm that the close interaction of the hybrid materials and good dispersion of Ni2P nanoparticles. The as-synthesized Ni2P/MoS2 hybrid electrocatalysts exhibit excellent activity with onset overpotential of 75mV and Tafle slope of 76mVdec−1, which are much better than that of pure MoS2. The enhanced stability of the as-prepared Ni2P/MoS2 for HER has also been observed. The improved performances for HER may be ascribed to the better conductivity and dispersion of MoS2 nanosheets in Ni2P/MoS2 hybrid electrocatalysts. The small size and good dispersion of Ni2P nanoparticles also contributed to the enhancement of HER activity. Compared with mechanically mixed MoS2 and Ni2P (Ni2P-MoS2), Ni2P/MoS2 hybrid materials demonstrate better electrochemical performances for HER, implying the existence of synergistic effect between Ni2P and MoS2 on HER activity.

Highly Efficient Oxygen and Hydrogen Electrocatalytic Activities of Self‐Morphogenic Nanoporous Carbon, Nitrogen Architectures

AbstractDesigning highly functional materials based on abundant elements is an important challenge. It would lead to a leap for energy conversion technology if a system comprising affordable material could work as electrocatalyst for important reactions in electrochemical energy storage and conversion and fuel production. This report shows simple nitrile chemistry as a new strategy to obtain nanoporous C,N architectures (npCNAs) with high activities for both the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER). The key is to control both morphology and chemical structure of the catalyst. The npCNAs showed the distinct four‐electron process in H2SO4 solution with a high activity of 7.7 mA mgcat−1 and an exchange current density (J0) of 2.81×10−10 A cm−2geo (Tafel slope=ca. 120 mV dec−1) for the ORR and at the same time an enhanced HER activity with J0=1.454×10−5 A cm−2geo.

MoSx supported graphene oxides with different degree of oxidation as efficient electrocatalysts for hydrogen evolution

A simple wet chemical method has been used to prepare MoSx in situ grown on graphene oxide (MoSx/GO) as a highly active and stable electrocatalyst for hydrogen evolution reaction (HER). The role of the oxygen-containing functional group on the surface of GO with different oxidation degrees have been studied for obtaining MoSx/GO with excellent electrochemical activity for HER. The electrochemical measurements show that MoSx/GO using the medium degree of oxidation of GO as matrix exhibits best electrocatalytic activity for HER with a small overpotential of ∼195 mV at the current density of 20 mA cm−2. A tafel slope of ∼47.7 mV per decade is obtained for MoSx/GO modified electrode. The turnover frequency per active site is calculated. Both the amount of active sites for HER and conductivity of the electrocatalyst have been greatly improved owing to the good dispersion and conductivity provided by GO matrix. Therefore, this work suggested that choosing GO with suitable oxidation degree as support is the key for synthesizing MoSx based electrocatalysts with enhanced HER activity.

3D arrays of molybdenum sulphide nanosheets on Mo meshes: Efficient electrocatalysts for hydrogen evolution reaction

Molybdenum sulphide has emerged as a promising electrocatalyst for hydrogen evolution reaction (HER). Toward further improving its activity, tremendous efforts have been made to preferentially expose active edge sites of molybdenum sulphide-based catalysts by engineering their surface structure. In this work, 3D arrays of molybdenum sulphide nanosheets were synthesized by hydrothermal treatment of Mo mesh in aqueous thiourea solution. Their compositional, morphological and structural properties as well as electrocatalytic activities were investigated in details. The results reveal that 3D arrays of molybdenum sulphide nanosheets demonstrate an enhanced HER activity with a low onset overpotential of 120mV and a Tafel slope of 46mV/dec, which is superior to that of 2D arrays molybdenum sulphide nanosheets grown on Mo foil. The high activity for HER can be ascribed to the superstructure of the catalysts with a large fraction of edge sites and a high surface area.

High-activity electrodeposited NiW catalysts for hydrogen evolution in alkaline water electrolysis

NiW alloy catalysts were prepared on a Cu foil substrate by using a co-electrodeposition method for use in the hydrogen evolution reaction (HER) in alkaline water electrolysis. The compositions of the alloy catalysts were controlled over a wide range by varying the molar ratio [W6+]/[Ni2+] in the electrolyte. At high W contents (∼41at.%) in the deposited catalyst, the morphologies of the NiW alloys showed drastic changes compared with those of electrodeposited Ni, in particular a significant decrease in surface coverage and aggregates’ sizes. All of NiW alloys deposited in a citrate-containing bath demonstrated an amorphous structure, regardless of W content. Electrochemical measurements employing repeated cyclic voltammetry (CV) showed enhanced HER activities for the NiW alloy catalysts compared with the pure Ni catalyst. The maximum HER activity was obtained with a W content of 41at.%; the alloying effects, including morphological changes, and the high affinity for hydrogen absorption shown by this alloy's amorphous structure are dominant factors in the enhanced HER activity. The results presented herein provide advanced information of significant relationship between material properties and HER activity of NiW alloys.

SDBS-assisted hydrothermal preparation and electrocatalytic properties of few-layer and edge-rich MoS2 nanospheres

MoS2 nanospheres assembled by few-layer (FL-) and edge-rich nanosheets with uniform sizes have been successfully synthesized by a facile anionic surfactant-assisted hydrothermal approach. The obtained samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and evaluated as electrochemical catalysts in the hydrogen evolution reaction (HER). It is found that the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) plays a crucial role in the formation of MoS2 nanosheets with few layers and rich exposed edges in our current synthetic route. As a result, the as-prepared FL-MoS2 nanosphere catalyst exhibits obviously enhanced HER activity such as more positive onset potential, larger current density as well as smaller Tafel slope of 65mVdec−1 in comparison with the pristine MoS2 sample due to the few-layer characteristics and rich exposed active edges.

Impact of a conductive oxide core in tungsten sulfide-based nanostructures on the hydrogen evolution reaction.

Tungsten oxide/tungsten sulfide (W18O49@WS2) core-shell nanorods prepared via a controlled sulfidization reaction of W18O49 nanowhiskers showed hydrogen evolution reaction (HER) activity superior to WS2 nanotubes, indicating the critical role of a highly conductive oxide core in enhancing HER activity.

Facile Synthesis of MoS2@CNT as an Effective Catalyst for Hydrogen Production in Microbial Electrolysis Cells

AbstractMicrobial electrolysis cells (MECs) can produce hydrogen gas from organic compounds in an energy‐efficient way by taking advantage of the potential generated by microorganisms. However, hydrogen evolution reaction (HER) in MECs is slow and thus requires catalysts. A challenge for MEC development therefore lies in the development of cost‐effective HER catalysts. In this study, a nanocomposite with molybdenum disulfide (MoS2) coated on highly conductive carbon nanotubes (CNTs) was synthesized as an alternative HER catalyst, and examined in an MEC for hydrogen production. Linear sweep voltammogram experiments demonstrated enhanced HER activity with increasing CNT content. The results suggest that conductivity may be the main limiting factor for overall HER catalysis by MoS2. MEC tests showed that MoS2/CNT‐90 achieved hydrogen production that was comparable to the Pt‐based catalyst. The low cost of the MoS2 composites will make it competitive as an effective HER catalyst for future MEC applications.