Electrode For Hydrogen Evolution Reaction Research Articles

Three-Dimensional Nanoporous Tungsten Disulfide/Acetylene Black Nanoflower Composite as Efficient Electrocatalyst for Enhanced Hydrogen Evolution Reaction.

A novel three-dimensional nanoporous tungsten disulfide/acetylene black (nanoporous-WS₂/AB) electrocatalyst was successfully prepared by template assisted hydrothermal method and further applied to hydrogen evolution reaction (HER) for the first time. Surface morphology and crystalline structure of as-prepared nanoporous-WS₂/AB were characterized by scanning electron microscopy and X-ray diffractometer. The electrocatalytic properties of as-prepared materials modified electrodes for HER were investigated by polarization curves, electrochemical impedance spectroscopy and Tafel polarization curves in 0.50 M H₂SO₄ solution. Compared with WS₂, AB and WS₂/AB based electrodes, nanoporous-WS₂/AB based electrode exhibited a much higher electrocatalytic activity which was attributed to the synergistic effect between nanoflower WS₂ and amorphous AB, as well as the presences of dual templates of amorphous AB and porous 4A-zeolite. The exchange current density of nanoporous-WS₂/AB electrode was 1.6 and 2.5 times larger than that of WS₂/AB and pure WS₂ based electrode at -400 mV, respectively. The results indicated that nanoporous-WS₂/AB composite would be a promising candidate for the potential application in HER.

Design of Highly Active Electrodes for Hydrogen Evolution Reaction Based on Mo-Rich Alloys Electrodeposited from Ammonium Acetate Bath

The given research was driven by prospects to design Mo-rich coatings with iron group metals electrodeposited from a highly saturated ammonium acetate bath. The obtained coatings could be employed as prominent electrodes for the hydrogen evolution reaction (HER). It was found that the Mo content in Ni–Mo alloys can be tuned from 30 to 78 at.% by decreasing the molar ratio [Ni(II)]:[Mo(VI)] in the electrolyte from 1.0 to 0.25 and increasing the cathodic current density from 30 to 100 mA/cm2. However, dense cracks and pits are formed due to hydrogen evolution at high current densities and that diminishes the catalytic activity of the coating for HER. Accordingly, smoother and crack-free Ni–54 at.% Mo, Co–52 at.% Mo and Fe–54 at.% Mo alloys have been prepared at 30 mA/cm2. Their catalytic behavior for HER has been investigated in a 30 wt.% NaOH solution at temperatures ranging from 25 to 65 °C. A significant improvement of electrocatalytic activity with increasing bath temperature was noticed. The results showed that the sequence of electrocatalytic activity in alkaline media decreases in the following order: Co–52 at.% Mo > Ni–54 at.% Mo > Fe–54 at.% Mo. These peculiarities might be linked with different catalytic behavior of formed intermetallics (and active sites) in electrodeposited alloys. The designed electrodeposited Mo-rich alloys have a higher catalytic activity than Mo and Pt cast metals.

Highly Efficient Hybrid Ni/Nitrogenated Graphene Electrocatalysts for Hydrogen Evolution Reaction.

Two nickel/nitrogenated graphene hybrid electrodes (Ni-NrGONH3 and Ni-NrGOAPTES) were synthesized, and their catalytic activity with respect to the hydrogen evolution reaction (HER) in alkaline media was analyzed. Incorporation of nitrogen to the carbon structure in graphene oxide (GO) or reduced GO (rGO) flakes in aqueous solutions was carried out based on two different configurations. NrGONH3 particles were obtained by a hydrothermal method using ammonium hydroxide as the precursor, and NGOAPTES particles were obtained by silanization (APTES functionalization) of GO sheets. Aqueous dispersions containing NrGONH3 and NGOAPTES particles were added to the traditional nickel Watts plating bath in order to prepare the Ni-NrGONH3 and Ni-NrGOAPTES catalysts, respectively. Nickel substrates were coated with the hybrid nickel electrodeposits and used as electrodes for hydrogen production. The Ni-NrGO catalysts show a higher activity than the conventional nickel electrodeposited electrodes, particularly the ones containing APTES molecules because they allow obtaining a hydrogen current density 130% higher than conventional Ni-plated electrodes with a Watts bath in the absence of additives. In addition, both catalysts show a low deactivation rate during the ageing treatment, which is a sign of a longer midlife for the catalyst. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were used for examination of the catalytic efficiency of hybrid Ni-NrGO electrodes for HER in KOH solution. High values of exchange current densities, 8.53 × 10–4 and 2.53 × 10–5 mA cm–2 for HER in alkaline solutions on Ni-NrGONH3 and Ni-NrGOAPTES electrodes, respectively, were obtained.

Cobalt and cobalt oxide supported on nitrogen-doped porous carbon as electrode materials for hydrogen evolution reaction

A facile method is proposed to prepare cobalt supported on nitrogen-doped porous carbon material with high graphitization degree by using chitosan as carbon source, urea as soft template and poloxamer as dispersant. The prepared cobalt-carbon material (Co@NPC) shows that uniformly distributed cobalt nanoparticles are encapsulated in nitrogen-doped porous carbon bundle with large specific surface area. When Co@NPC is applied as electrode in hydrogen evolution reaction, it exhibits superior electrocatalytic performance with low overpotential (η10 = 259 mV), small Tafel slope (99 mV dec−1) and high stability with 83% of its original current density remained after 6 h electrochemical test in 1 M potassium hydroxide electrolyte.

Optimized Nickel-Cobalt and Nickel-Iron Oxide Catalysts for the Hydrogen Evolution Reaction in Alkaline Water Electrolysis

Ni and Ni-doped with transition metals (TM) such as Fe and Co represent the most suitable electrodes for hydrogen evolution reaction (HER) in alkaline media. Various compositions of co-precipitated Ni1 + xFe2 − xO4 and Ni1 + yCo2 − yO4 nanoparticles were investigated. The intrinsic HER catalytic activity is the same for all the catalysts, which we relate to similar values of the iso-electric point (IEP). However, the mass catalytic activity of the catalysts changes through a modification of the electrochemical surface area. Fractional reaction orders for hydrogen evolution revealed in all catalyst compositions are due to double layer effects and surface acid-base equilibria. Reaction order and Tafel slope of the catalysts are compatible with electrochemical adsorption as the rate-determining step for the HER. Tafel slopes were also evaluated independently from impedance spectroscopy, in good agreement with the polarization curves. Electrodes prepared from catalyst inks containing an anion-exchange ionomer displayed inferior catalytic activity for the HER as compared to electrodes prepared with Nafion in the ink. Chronoamperometry confirmed the sustained superior hydrogen kinetics over time of NiFe2O4 and NiCo2O4 composition over that of NiO.

Optimizing hydrogen evolution activity of nanoporous electrodes by dual-step surface engineering

The hydrogen evolution reaction (HER) from electrocatalytic water splitting represents an important approach for efficient hydrogen production, in which the HER feasibility relies on electrocatalysts as well as the art of electrode design. Herein, a considerate surface engineering strategy is developed for promoting HER process taking place on nanoporous HER electrodes. Cobalt nanopore arrays (CoNPA) are fabricated as the representative nanoporous HER electrode. Then an ultrathin titanium dioxide (TiO2) with optimized thickness is conformally coated onto CoNPA for improving the wettability in order to expose more active sites, followed by a well-dispersed platinum (Pt) nanoparticles with an ultralow mass loading (ca. 54 μg cm−2) anchored on TiO2 layer for enhancing the HER activity. The advanced features of nanoporous architecture in combination with the synergistic contribution from ultrathin TiO2 layer and well-dispersed Pt nanoparticles enable CoNPA@TiO2@Pt electrode exhibit outstanding HER performance in alkaline conditions, i.e., an overpotential of 29 mV needed to reach the catalytic current density of 10 mA cm−2 and long-termed performance as well as structure stability. Not limited to the HER electrodes, the similar strategy is also expected to be further applied to the rational design and nanoengineering of electrodes for other electrochemical energy conversion and storage devices.

Layer-stacking porous WCx nanoparticles on carbon cloth as self-supported integrated electrode for hydrogen evolution reaction

Tungsten carbide (WC), possessing Pt-like properties and excellent stability in acidic and basic media, has been significantly considered as the most promising candidate to replace to the commercial Pt/C for electrocatalyzing hydrogen evolution reaction (HER). However, high-temperature carburizing process is an indispensable step for the preparation of the WC-based nanomaterials, leading to the agglomeration of amounts of WC crystal particles, which is not favorable for exposing the high density of active sites. Here, we innovatively in-situ constructed a self-supporting integrated electrode, layer-stacking porous WCx nanoparticles decorated onto carbon cloth (denoted as WCx@CC). Benefiting from the faulting porous structure, it not only enables to accelerate the mass transport from two directions of parallel and vertical to carbon fiber but also simultaneously provide more active sites accessibility. Consequently, this novel integrated electrode exhibits the excellent performance with a small onset potential of 70 mV, and Tafel slope of 79 mV/dec in acidic media. Impressively, the WCx@CC electrode could sustain more than 12 h of hydrogen production at a constant potential of −0.3 V without observable deterioration in acidic media.

Electrocatalytic Activities of Macro- Porous Nickel Electrode for Hydrogen Evolution Reaction in Alkaline Media

Alkaline water electrolysis is one of the easiest methods for hydrogen production, offering the advantages of simplicity, high purity and low cost. Nickel and other transi-tion metal such as (Ni, Co, Fe and Mo) 3 D porous foams are an exciting family of cata-lysts for hydrogen production in alkaline electrolytes because of their special corrosion resistance and highly intrinsic electrocatalytic activity toward HER. In this work, macro porous Ni electrodes have been developed by dynamic hydrogen template electrodeposi-tion (DHTE) on stainless steel (AISI 304) substrates. Macro porous Ni electrodes with pore size ranging for 1.3-9.41 µm were synthesized by galvanostatic deposition at high current densities. Higher current density and longer deposition time lead to coarsening of pore size obtained. On the other hand, increasing the concentration of NH4Cl additives lead to a remarkable reduction in pore size. The activity for hydrogen evolution reaction (HER) on the obtained layers was evaluated by using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in 10 % KOH solution. The electrochemical tests results showed that Ni deposit with fine pore size (1.7 µm) mani-fests the highest intrinsic activity for HER.

NiGa modified carbon-felt cathode for hydrogen production

In this study, known electrocatalytic active metal nickel and low amount of gallium were electrodeposited on carbon felt electrode for hydrogen evolution reaction in alkali medium. Morphological and structural analyses of prepared electrodes were determined by scanning electron microscopy and energy dispersive X-ray spectroscopy. The electrocatalytic activity of obtained electrodes for hydrogen evolution reaction was determined with cathodic polarization curves, electrochemical impedance spectroscopy, discharge potential measurements, hydrogen volume measurements at constant potential and durability tests. It was found that the electrodeposition of low amount of gallium over the nickel coated carbon felt electrode increases the hydrogen evolution reaction activity and decreases the overpotential for hydrogen region. The electrocatalytic activity of nickel and gallium deposited on carbon felt electrode was explained with active sites of surface and synergistic effect of nickel and gallium created by high surface area of carbon felt.

Synergistic electrocatalytic effect of Pd and Rh nanoislands co-deposited on Au(poly) on HER in alkaline solution

Hydrogen evolution reaction (HER) was explored on tri-metallic Rh@Pd/Au(poly) and bimetallic Pd/Au(poly) and Rh/Au(poly) electrodes in alkaline solution. Electrodes were prepared by the spontaneous deposition of either Pd or Rh and by co-deposition of both Rh and Pd on polycrystalline gold electrode. Characterization of modified electrodes was performed by cyclic voltammetry in alkaline solution, while additional information about phase analysis, chemical composition and surface morphology of tri-metallic Rh@Pd/Au(poly) electrode were acquired using X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy and atomic force microscopy. Investigations of HER catalysis have shown that the activity of tri-metallic Rh@Pd/Au(poly) electrode exceeds the activities of both Pd/Au(poly) and Rh/Au(poly) electrodes, meaning that the synergism between co-deposited Pd and Rh islands is achieved. Moreover, Rh@Pd/Au(poly) electrode showed significant approach to the activities of bulk Pd and Rh electrodes for HER, especially when taking into account low activity of bare Au substrate. Synergistic effect of co-deposited Pd and Rh islands is a consequence of the strong electronic interaction between three metals in a close contact, which promotes the activity for HER by lowering the adsorption energy of Hads intermediate.

Self-supported transition metal phosphide based electrodes as high-efficient water splitting cathodes

Electrolytic water splitting has been considered as a promising technology to produce highly pure H2 by using electrical power produced from wind, solar energy or other fitful renewable energy resources. Combining novel self-supporting structure and high-performance transition metal phosphides (TMP) shows substantial promise for practical application in water splitting. In this review, we try to provide a comprehensive analysis of the design and fabrication of various self-supported TMP electrodes for hydrogen evolution reaction, which are divided into three categories: catalysts growing on carbon-based substrates, catalysts growing on metal-based substrates and freestanding catalyst films. The material structures together with catalytic performances of self-supported electrodes are presented and discussed. We also show the specific strategies to further improve the catalytic performance by elemental doping or incorporation of nanocarbons. The simple and one-step methods to fabricate self-supported TMP electrodes are also highlighted. Finally, the challenges and perspectives for self-supported TMP electrodes in water splitting application are briefly discussed.

Ni-doped amorphous iron phosphide nanoparticles on TiN nanowire arrays: An advanced alkaline hydrogen evolution electrocatalyst

Efficient and low-cost non-precious-metal-based electrocatalysts are crucial to the commercial success of the hydrogen evolution reaction (HER) under alkaline conditions. Herein, a step-by-step strategy to prepare a hierarchical structure assembled from Ni-doped amorphous FeP nanoparticles, porous TiN nanowires, and graphitic carbon fibers (Ni-FeP/TiN/CC) is described. The FeP/TiN/CC composite is plasma-implanted with Ni ions to modify the electronic structure and produce an amorphous surface. Simultaneous doping and amorphization of FeP by Ni ion implantation to enhance the HER activity is achieved for the first time. The flexible and freestanding Ni-FeP/TiN/CC catalyst produced on a carbon cloth can serve directly as an electrode in HER in an alkaline medium. The Ni-FeP/TiN/CC catalyst delivers excellent HER performance including an overpotential of 75 mV to generate a cathodic current density of 10 mA cm−2, a Tafel slope close to that of commercial Pt/C catalysts, and long lifetime indicated by a more constant cathodic current density during continuous operation for 10 h. The remarkable HER activity is attributed to the combined effects rendered by the Ni and Fe atoms in the Ni-doped FeP nanoparticles, active amorphous surface, as well as conductive nanowire scaffold, which expose a large amount of active sites, enhance the charge transfer efficiency, and prevent the catalysts from migration and aggregation.

Self-Supported NiSe2 Nanowire Arrays on Carbon Fiber Paper as Efficient and Stable Electrode for Hydrogen Evolution Reaction

NiSe2 nanowire (NW) arrays grown on flexible carbon fiber paper (CFP) were synthesized, for the first time, through a novel thermal selenization method in vacuum instead of flowing inert gas. The u...

Cobalt–Cobalt Phosphide Nanoparticles@Nitrogen‐Phosphorus Doped Carbon/Graphene Derived from Cobalt Ions Adsorbed Saccharomycete Yeasts as an Efficient, Stable, and Large‐Current‐Density Electrode for Hydrogen Evolution Reactions

AbstractDevelopment of electrocatalysts for hydrogen evolution reaction (HER) with low overpotential and robust stability remains as one of the most serious challenges for energy conversion. Herein, a serviceable and highly active HER electrocatalyst with multilevel porous structure (Co‐Co2P nanoparticles@N, P doped carbon/reduced graphene oxides (Co‐Co2P@NPC/rGO)) is synthesized by Saccharomycete cells as template to adsorb metal ions and graphene nanosheets as separating agent to prevent aggregation, which is composed of Co‐Co2P nanoparticles with size of ≈104.7 nm embedded into carbonized Saccharomycete cells. The Saccharomycete cells provide not only carbon source to produce carbon shells, but also phosphorus source to prepare metal phosphides. In order to realize the practicability and permanent stability, the binderless and 3D electrodes composed of obtained Co‐Co2P@NPC/rGO powder are constructed, which possess a low overpotential of 61.5 mV (achieve 10 mA cm−2) and the high current density with extraordinary catalytic stability (1000 mA cm−2 for 20 h) in 0.5 m H2SO4. The preparation process is appropriate for synthesizing various metal or metal phosphide@carbon electrocatalysts. This work may provide a biological template method for rational design and fabrication of various metals or metal compounds@carbon 3D electrodes with promising applications in energy conversion and storage.

Phosphorus-doped graphene supported palladium (Pd/PG) electrocatalyst for the hydrogen evolution reaction in PEM water electrolysis

ABSTRACTPEM water electrolysis is one of the most efficient methods for the production of hydrogen because of produced high purity of the gases and environmentally friendly. In the present study, Phosphorus-doped Graphene (PG) was synthesized by thermal annealing of triphenylphosphine (TPP) and graphene oxide (GO). The PG supported palladium (Pd/PG) electrocatalysts were synthesized by chemical reduction method and used as the cathode for hydrogen evolution reaction (HER) electrode. Structural properties and electrochemical performances of the synthesized Pd/PG electrocatalyst were studied by FE-SEM, EDS, ICP, FT-IR, XRD, and Cyclic voltammetry (CV) methods, respectively. The membrane electrode assemblies (MEA’s) were fabricated using Pd/PG as cathode for HER electrode and RuO2 as anode for OER electrode. Also, their electrochemical performances along with the corresponding hydrogen yields were evaluated in single cell PEM water electrolyzer at various experimental conditions such as different current densities from 0.1 to 2.0 A cm−2 and temperatures (28–80°C). The synthesized Pd/PG electrocatalyst was observed a current density of 1 A cm−2 with 1.95 V at 80°C. Further, long-term stability studies were carried out continuously up to 2000 h which showed a reasonable stability. Hence, the synthesized Pd/PG can be used as an alternative to Pt-based electrocatalysts for the HER in PEM water electrolysis.

Electrodeposition of nano-nickel in deep eutectic solvents for hydrogen evolution reaction in alkaline solution

The electrodeposition of nano-Ni films on a Cu substrate from NiCl2 precursors in choline chloride (ChCl)/urea or ethylene glycol (EG) based deep eutectic solvent (DES) was illustrated. Voltammetric study demonstrates that the electrodeposition of Ni(Ⅱ) in both ChCl/urea and ChCl/EG systems is a simple one-step reaction process, and the electrochemical process is a typical diffusion-controlled irreversible process. The obtained Ni films can be controlled to form nanostructures depending on the DES and the electrodeposition conditions. The nanostructured Ni films were investigated as electrodes for hydrogen evolution reaction (HER) in an alkaline medium. The enhanced catalytic activity toward the HER was confirmed, which is mainly attributed to the formation of needles morphology and the improved electrochemical surface area. The result reveals that the electrodeposition process may provide a promising strategy for the production of nano-Ni at low temperature for HER.

Network-like porous Co-Ni-B grown on carbon cloth as efficient and stable catalytic electrodes for hydrogen evolution

We reported a network-like porous amorphous Co-Ni-B grown on carbon cloth (CC) through a facile one-step chemical reduction process which was used as a binder-free three dimension (3D) integrated electrode for hydrogen evolution reaction (HER). The Co-Ni-B/CC with Co/Ni molar ratio about 1:1 (Co-50Ni-B/CC) exhibited the best HER performance in alkaline medium, with a negligible onset overpotential (22 mV), a small Tafel slope (88.2 mV dec−1) and excellent long-term stability. Specially, the HER activity of Co-50Ni-B/CC even exceeds that of commercial Pt/C at sufficiently high overpotential. The excellent HER performance of the Co-Ni-B/CC is attributed to a large number of active sites, the enhanced electron transfer process and the robust contact between catalyst and CC substrate.

Few Layered N, P Dual‐Doped Carbon‐Encapsulated Ultrafine MoP Nanocrystal/MoP Cluster Hybrids on Carbon Cloth: An Ultrahigh Active and Durable 3D Self‐Supported Integrated Electrode for Hydrogen Evolution Reaction in a Wide pH Range

AbstractDevelopment of highly active and stable electrocatalysts is a key to realize efficient hydrogen evolution through water electrolysis. Here, the development of a 3D self‐supported integrated electrode constituting few layered N, P dual‐doped carbon‐encapsulated ultrafine MoP nanocrystal/MoP cluster hybrids on carbon cloth (FLNPC@MoP‐NC/MoP‐C/CC) is demonstrated. Benefiting from novel structural features including fully open and accessible nanoporosity, ultrasmall size of MoP‐NCs on MoP‐Cs as well as strong synergistic effects of N, P dual‐doped carbon layers with MoP‐NCs, the FLNPC@MoP‐NC/MoP‐C/CC as a 3D self‐supported binder‐free integrated electrode exhibits extraordinary catalytic activity for the hydrogen evolution reaction (HER) with extremely low overpotentials at all pH values ( j = 10 mA cm−2 at η = 74, 106, and 69 mV in 0.5 m H2SO4, 1.0 m PBS, and 1.0 m KOH electrolytes, respectively). To the best of our knowledge, the ultrahigh electrocatalytic performance represents one of the best MoP‐based HER electrocatalysts reported so far. Additionally, few layered N, P dual‐doped carbon can effectively prevent MoP‐NC/MoP‐C from corrosion, making the FLNPC@MoP‐NC/MoP‐C/CC exhibit nearly unfading stability after 50 h testing in acidic, neutral, and alkaline media, which shows great promise for electrocatalytic water splitting application.

Hierarchical MoS2 nanoflowers on carbon cloth as an efficient cathode electrode for hydrogen evolution under all pH values

In this paper, a facile hydrothermal synthetic strategy was developed for MoS2 nanoflowers with enlarged interlayer spacing on the carbon cloth (CC) as a high efficiency cathode electrode for hydrogen evolution reaction (HER) under wide pH condition. It was observed that the loading amount of MoS2 has a major impact on the HER performance, where the optimized MoS2/CC exhibited a low onset potential of 94 mV and a small Tafel slope of 50 mV dec−1 in strong acid solution (pH = 0). The improved HER performance can be contributed to the enlarged interlayer spacing, abundant defects and more exposed active sites in the small size MoS2 nanosheets as revealed by XRD and HRTEM. Meanwhile, it also exhibited relatively good performance for HER under basic and neutral conditions with the overpotentials of 188 (pH = 14) and 230 (pH = 7) mV to achieve current density of 10 mA cm−2 and the Tafel slopes of 52 and 84 mV dec−1, respectively.

One-step co-electrodeposition of hierarchical radial NixP nanospheres on Ni foam as highly active flexible electrodes for hydrogen evolution reaction and supercapacitor

Considering the synergistic effect of transition metal phosphides and 3D structure substrates, herein, we directly deposited well-defined hierarchical radial NixP nanospheres on Ni foam via a facile, one-step co-electrochemical method to function as highly active flexible electrodes for both hydrogen evolution reaction and supercapacitor. Impressively, the bifunctional NixP/NF electrode requires an overpotential of only 63 mV to achieve a current density of 10 mA cm−2 and demonstrates a low Tafel slop of 55 mV dec−1 in 1 M KOH. Moreover, the electrochemical supercapacitor based on this hierarchical NixP/NF electrode also shows a superior specific capacitance of 1684 mF cm−2 (382.7 F/g) at a current density of 2 mA cm−2 and an outstanding retention ratio of 110.9% of its original capacitance value after 4000 cycles in 6 M KOH. Hopefully, excellent electrochemical performances demonstrate that this NixP/NF material could be a promising candidate for future applications in both hydrogen evolution reactions and supercapacitors.