An infinite chain, {[Ni(tn)2]3[Fe(CN)4(μ-CN)2]2}n,a new catalyst for electrochemical-driven water splitting and photochemical-driven hydrogen evolution from water under blue light

A new catalyst for both water reduction and oxidation, based on an infinite chain, {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n, is formed by the reaction of NiCl₂, 1,3-propanediamine (tn) and K₃ [Fe(CN)₆]. {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n can electro-catalyze hydrogen evolution from a neutral aqueous buffer (pH 7.0) with a turnover frequency (TOF) of 1561 mol of hydrogen per mole of catalyst per hour (H₂/mol catalyst/h) at an overpotential (OP) of 837 mV {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n also can electro-catalyze O₂ production from water with a TOF of ～45 mol O₂ (mol cat)^?1s^?1 at an OP of 591 mV. Under blue light (λ = 469 nm), together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H₂A) as a sacrificial electron donor, {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n can photo-catalyze hydrogen generation from an aqueous buffer (pH 4.0) with a turnover number (TON) of 11,450 mol H₂ per mole of catalyst (mol of H₂ (mol of cat)^?1) during 10 h irradiation. The average of apparent quantum yield (AQY) is as high as 40.96% during 10 h irradiation. Studies indicate that {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n exists in two forms: a cyano-bridged chain ({[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n) in solid, and a salt ([Ni(tn)₂]₃ [Fe(CN)₆]₂) in aqueous media; Catalytic reaction occurs on the nickel center of [Ni(tn)₂]²⁺, and the introduction of [Fe(CN)₆]^3- can improve the catalytic efficiency of [Ni(tn)₂]²⁺ for H₂ or O₂ generation. We hope these findings can afford a new method for the design of catalysts for both water reduction and oxidation.     

Interlaced rosette-like MoS2/Ni3S2/NiFe-LDH grown on nickel foam: A bifunctional electrocatalyst for hydrogen production by urea-assisted electrolysis

In targeting the most important energy and environmental issues in current society, the development of low-cost, bifunctional electrocatalysts for urea-assisted electrocatalytic hydrogen (H₂) production is an urgent and challenging task. In this work, interlaced rosette-like MoS₂/Ni₃S₂/NiFe-layered double hydroxide/nickel foam (LDH/NF) is successfully synthesized by a two-step hydrothermal reaction. Due to its unique interlaced heterostructure, MoS₂/Ni₃S₂/NiFe-LDH/NF exhibits excellent bifunctional catalytic activity towards the urea oxidation reaction (UOR) and the hydrogen evolution reaction (HER) in 1.0 M KOH with 0.5 M urea. In a concurrent two-electrode electrolyser (MoS₂/Ni₃S₂/NiFe-LDH/NF(+,-)), only voltage of 1.343 V is required to reach 50 mA cm⁻², which is 216 mV lower than for pure water splitting. Furthermore, after 16 h of urea electrolysis in 1.0 M KOH with 0.5 M urea, the current density remains at 98% of the original value. Thus, the catalyst is not only favorable for H₂ production, but also has great significance for the problem of urea-rich wastewater treatment.     

A molecular Keggin polyoxometalate catalyst with high efficiency for visible-light driven hydrogen evolution

A molecular Keggin polyoxometalate catalyst K₇[Co^IIICo^II(H₂O)W₁₁O₃₉](1) was successfully synthesized and efficiently catalyzed the hydrogen evolution. To the best of our knowledge, the molecular Keggin polyoxometalate catalyst 1 is the first reported polyoxometalate containing cobalt with efficient hydrogen production activity under the visible light irradiation. Under the optimal photocatalytic condition (photoirradiation at λ ≥ 420 nm, Eosin-Y as the photosensitizer, triethanolamine as the electron donor and Pt produced in situ photoreduction as co-catalyst), the turnover number (TON/based on catalyst) reached as high as 100; the initial quantum yield and the initial turnover frequency (TOF) at the first 10 min were 29% and 0.025 s⁻¹, respectively. The hydrogen evolution average rate of 1 achieved 13,395 μmol h⁻¹ g⁻¹, as far as we are concerned, which is the highest among all the polyoxometalates photocatalytic systems reported so far. A possible mechanism of the hydrogen evolution reaction was proposed on the basis of steady-state fluorescence decay studies.     

Hollow hexagonal NiSe–Ni3Se2 anchored onto reduced graphene oxide as efficient electrocatalysts for hydrogen evolution in wide-pH range

Integrating transition metal complexes with carbon-based materials, especially graphene, is a useful strategy for synthesizing effective hydrogen evolution catalysts. Herein, we report a design of hollow hexagonal NiSe–Ni₃Se₂ nanosheets grown on reduced graphene oxide (NiSe–Ni₃Se₂/rGO) by a simple hydrothermal method as an effective catalyst for hydrogen evolution reaction (HER) in the full pH range. In 0.5 M H₂SO₄, the NiSe–Ni₃Se₂/rGO possesses 112 mV to achieve 10 mA cm^?2 and a small Tafel slope (61 mV dec^?1). In 1.0 M PBS and 1.0 M KOH, the overpotentials are 261 and 188 mV at 10 mA cm^?2, and Tafel slopes are 103 and 92 mV dec^?1, respectively. Meanwhile, it owns good cycle stability and durability over 20 h in the whole pH range (0-14). In all solutions, the HER performance of NiSe–Ni₃Se₂/rGO is better than that of NiSe–Ni₃Se₂. This is because the rGO substrate accelerates the electron transfer and improves the electrical conductivity, increasing HER activity of catalyst.     

Electrocatalytic hydrogen evolution by Co(II) complexes of bistriazolylpyridines

Two cobalt complexes [Co(L₁)₂](ClO₄)₂⋅4CH₃CN (1) and [Co(L₂)₂](ClO₄)₂⋅2CH₃CN⋅0.5H₂O (2) of the new click-derived bistriazolylpyridines 2,6-bis(1-(pyridin-2-yl)-1H-1,2,3-triazol-4-yl)isonicotinate methyl ester (L₁) and 2,6-bis-(1-methoxycarbonylmethyl-1H-1,2,3-triazol-4-yl)isonicotinate methyl ester (L₂) were synthesized and characterized. The electrocatalytic hydrogen evolution reaction (HER) mediated by complexes 1 and 2 was studied in CH₃CN in the presence of acetic acid. Both complexes catalyzed HER with low overpotentials and high Faradaic efficiencies (370 mV and 93% for 1, 300 mV and 95% for 2). The distal substituents on the triazolyl moiety of the bistriazolylpyridines have apparent impacts on the redox and catalytic properties of 1 and 2. The catalytic behaviors were further studied using spectroelectrochemistry and the reductant cobaltocene. It was found that the reduction of the bistriazolylpyridines was necessary for the catalytic activity. Plausible pathways were proposed for the HER mediated by 1 and 2. This work provided some hints for the preparation of HER catalysts based on the redox-active triazolylpyridine ligands.     

Porous flower-like nickel nitride as highly efficient bifunctional electrocatalysts for less energy-intensive hydrogen evolution and urea oxidation

Finding a suitable replacement for the high potential of anodic water electrolysis (oxygen evolution reaction (OER)) is significant for hydrogen energy storage and conversion. In this work, a simple and scalable method synthesizes a structurally unique Ni₃N nanoarray on Ni foam, Ni₃N-350/NF, that provides efficient electrocatalysis for the urea oxidation reaction (UOR) that transports 10 mA cm⁻² at a low potential of 1.34 V. In addition, Ni₃N-350/NF exhibits electro-defense electrocatalytic performance for hydrogen evolution reaction, which provides a low overpotential of 128 mV at 10 mA cm⁻². As proof of concept, all-water-urea electrolysis measurement is carried out in 1 M KOH with 0.5 M Urea with Ni₃N-350/NF as cathode and anode respectively. Ni₃N-350/NF||Ni₃N-350/NF electrode can provide 100 mA cm⁻² at a voltage of only 1.51 V, 160 mV less than that of water electrolysis, which proves its commercial viability in energy-saving hydrogen production.     

Fabrication of robust CoP/Ni2P/CC composite for efficient hydrogen evolution reaction and the reduction of graphene oxide

Developing the novel catalysts with an excellent performance of hydrogen generation is essential to facilitate the application of hydrogen evolution reaction (HER). Herein, a heterostructured cobalt phosphide/nickel phosphide/carbon cloth (CoP/Ni₂P/CC) composite was fabricated via an interfacial engineering strategy to achieve the modification of CoP nanoleaf on Ni₂P nanosheet skeleton supported by carbon cloth. By virtue of the unique heterostructure, abundant exposing active sites and the synergistic coupling effect of CoP and Ni₂P nanoparticles, the elaborated CoP/Ni₂P/CC composite exhibits a robust catalytic property. Among fabricated composites, the optimal CoP/Ni₂P/CC-4 catalyst behaves an excellent HER performance at a wide pH range (overpotentials of 67, 71 and 95 mV to afford 10 mA cm^?2 in 0.5 M H₂SO₄, 1 M KOH and 1 M PBS, respectively). The HER current density of this composite shows a negligible degradation after continuous test for 24 h. Charmingly, the HER process of this catalyst was innovatively applied to reduce graphene oxide, and thus exploiting the fabrication route of reduced graphene oxide (rGO). We are sure that this work will provide a firm guideline for the exploitation of pH-universal HER catalysts and the exploration of HER application.     

Three-dimensional hierarchically porous iridium oxide-nitrogen doped carbon hybrid: An efficient bifunctional catalyst for oxygen evolution and hydrogen evolution reaction in acid

Active and durable acid medium electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are of critical importance for the development of proton exchange membrane (PEM) water electrolyser or Fuel cells. Herein, we report a facile method for the synthesis of 3D-hierarchical porous iridium oxide/N-doped carbon hybrid (3D-IrO₂/N@C) and its superior OER and HER activity in acid. In 0.5 M HClO₄, this catalyst exhibited remarkable activity towards OER with a low overpotential of 280 mV at 10 mA/cm² current density, a low Tafel slope of 45 mV/dec and ∼98% faradaic efficiency. The mass activity (MA) and turnover frequency (TOF) are found to be 833 mA/mg and 0.432 s⁻¹ at overpotential of 350 mV which are ∼32 times higher than commercial (comm.) IrO₂. The HER performance of this 3D-IrO₂/N@C is comparable with comm. Pt/C catalyst in acid. This 3D-IrO₂/N@C catalyst requires only 35 mV overpotential to reach a current density 10 mA/cm² with Tafel slope 31 mV/dec. Most importantly, chronoamperometric stability test confirmed superior stability of this catalyst towards HER and OER in acid. This 3D-IrO₂/N@C catalyst was applied as both cathode and anode for over-all water splitting and required only 1.55 V overpotential to achieve a current density of 10 mA/cm² in acid. The outstanding activity of the 3D-IrO₂/N@C catalyst can be attributed to a unique hierarchical porous network, high surface area, higher electron and mass transportation, synergistic interaction between IrO₂ and carbon support.     

Facile hydrothermal synthesis of rare earth phosphate for boosting hydrogen evolution reaction

The water electrolysis process has attracted great attention due to the production of high energy density pure hydrogen. However, the involved cell reactions in this process such as hydrogen and oxygen evolution reactions are kinetically sluggish and demands high input energy to accelerate the rate of these reactions. Therefore, the development and application of efficient electrocatalyst is essential for hydrogen evolution reaction (HER) as well as oxygen evolution reaction (OER). In the present work, we have successfully synthesized two rare earth phosphates through the hydrothermal route and used as a catalysts towards HER in an acidic medium. The rare earth phosphate PrPO₄ exhibits better catalytic activity than YPO₄ catalyst. The overpotential of PrPO₄, YPO₄ and standard Pt/C were found as 147, 484.3 and 58 mV vs. reversible hydrogen electrode, respectively, to reach current density 10 mA·cm^?2 and corresponding Tafel slopes were found as 107.58, 118.73 and 80.89 mV decade^?1, respectively in 0.5 M H₂SO₄. The catalytic activity of PrPO₄ (472.83 mA·cm^?2) overcome standard Pt/C (179.60 mA·cm^?2) at high overpotential 450 mV vs. reversible hydrogen electrode. The prepared PrPO₄ shows efficient electrocatalytic activity towards HER in acidic medium because it possess high BET surface area, large ECSA value and small charge transfer resistance than YPO₄.     

Interfacial coupling effect of CoO/CoMoO4 promotes alkaline hydrogen electrode for hydrogen energy storage system

Herein, CoO and CoMoO₄ heterostructure supported on nickel foam (CoO/CoMoO₄@NF) are proposed as an effective bifunctional hydrogen evolution reaction (HER) and hydroxide reaction (HOR) electrocatalyst. The electron density distribution at the interface can be optimized by coupling CoO and CoMoO₄, thereby improving conductivity and regulating the hydrogen binding energy (HBE) and hydroxyl binding energy (OHBE). CoO/CoMoO₄@NF exhibits high stability and activity with an exchange current density of ∼3.67 mA cm⁻². Co/CoMoO₄@NF reaches the current density of −10 mA cm⁻² at only −29 mV and the corresponding Tafel slope of 40.2 mV dec⁻¹. This work provides a promising solution for non-precious metal catalyst for hydrogen reaction in energy storage.     

Nickel doped MoS2 nanoparticles as precious-metal free bifunctional electrocatalysts for glucose assisted electrolytic H2 generation

Hydrogen, as the one of clean energy source, has the advantages of high energy density and carbon-free emission. Water electrolysis is one of the most promising ways to generate hydrogen, but the rather high energy required seriously hinders its widespread applications yet. In this study, we report an alkaline electrolyzer to implement energy-saving H₂ generation by coupling cathodic hydrogen evolution reaction (HER) with anodic glucose oxidation reaction (GOR) other than oxygen evolution reaction, in which nickel-doped MoS₂ nanoparticles (Ni–MoS₂ NPs) has been developed as bifunctional electrocatalyst for HER and GOR. The electrolyzer only requires a cell voltage of 1.67 V to reach an electrolysis current density of 10 mA cm⁻², about 270 mV lower than the corresponding value in the traditional electrolyzer. Electrolytic H₂ generation with the assistance of biomass derived materials may open a new way for the future sustainable development.     

Nickel phosphide decorated Pt nanocatalyst with enhanced electrocatalytic properties toward common small organic molecule oxidation and hydrogen evolution reaction: A strengthened composite supporting effect

In this paper, well-dispersed Ni₂P-NiP₂-Pt/CNTs catalyst promoted by nickel-phosphorus compounds was readily synthesized by a two-step hydrothermal process. The as-synthesized Ni₂P-NiP₂-Pt/CNTs displayed improved electrocatalytic properties towards electro-oxidation of common small organic fuels such as methanol, ethanol and formic acid in contrast with Pt/CNTs and Pt/CNPs in acidic electrolytes. Meanwhile, the Ni₂P-NiP₂-Pt/CNTs catalyst also exhibited the excellent performance toward hydrogen evolution reaction with a more negative onset potential (?15 mV) and a smaller Tafel slope (29.8 mV dec^?1) when compared with Pt/CNTs (?29 mV, 30.6 mV dec^?1) and Pt/CNPs (?32 mV, 31.3 mV dec^?1) in 1.0 M H₂SO₄ solution. The catalytic activity enhancement possibly derives from the induced large specific surface area of carbon nanotubes as well as the strengthened synergistic effect between multiple supporting interactions.     

Synthesis of functional Ni2P/CC catalyst and the robust performances in hydrogen evolution reaction and nitrate reduction

The non-precious transition metal phosphides (TMPs) as robust and effective hydrogen evolution reaction (HER) catalysts have attracted enormous attention, due to the merits of earth-abundance, low price, desirable stability and high efficiency. However, the conventional preparation process of this kind of catalyst is inconvenient. Herein, we report a facile approach toward the fabrication of nickel phosphide (Ni₂P) assembled on carbon cloth (CC) via the coupling method of electroless plating and low temperature phosphorization. Then, the crystallinity, morphology and chemical component of fabricated self-supporting Ni₂P/CC catalyst employed for the HER process were characterized, and the HER property was successively evaluated in three types of electrolytes (i.e., acidic, neutral and alkaline solutions). The as-prepared Ni₂P/CC catalyst displays a remarkable HER performance, which can be corroborated by the small Tafel slope (b = 50 mV dec⁻¹), high exchange current density (j₀ = 6.6 × 10⁻² mA cm⁻²), acceptable overpotential (119 mV) to attain the current density of 10 mA cm⁻², as well as the superb stability (<5% decay after 24 h potentiostatic test) in 0.5 M H₂SO₄. In addition, it should be noted that the HER process of Ni₂P/CC catalyst can be competent for the reduction of nitrate from the solution, and an efficiency of 63.2% for this nutrient pollutant is achieved.     

Ni3Mo3N coupled with nitrogen-rich carbon microspheres as an efficient hydrogen evolution reaction catalyst and electrochemical sensor for H2O2 detection

Hydrogen evolution reaction (HER) and electrochemical analysis are two important fields of electrochemical research at present. We found that both HER and some electrochemical analytical reactions relied on the concentration of hydrogen ions (H⁺) in solution, so we intended to develop an electrode material that is sensitive to H⁺ and can be used for both HER and some electrochemical analyses. In this work, we synthesized Ni₃Mo₃N coupled with nitrogen-rich carbon microspheres (Ni₃Mo₃N@NC MSs) as highly efficient electrode material for HER and detection of Hydrogen peroxide (H₂O₂), which plays an important role in physiological processes. Here the aniline was used as the nitrogen and carbon sources to synthesize Ni₃Mo₃N@NC. The Ni₃Mo₃N@NC MSs showed high performance for HER in 1 M KOH solution with a small overpotential of 51 mV at 10 mA cm^?2 and superior stability. For H₂O₂ detection, a detection limit of 1 μM (S/N = 3), sensitivity of 120.3 μA·mM^?1 cm^?2 and linear range of 5 μM–40 mM can be achieved, respectively. This work will open up a low-cost and easy avenue to synthesize transition metal nitrides coupled with N-doped carbon as bifunctional electrode material for HER and electrochemical detection.     

Ru-doped 3D porous Ni3N sphere as efficient Bi-functional electrocatalysts toward urea assisted water-splitting

Developing efficient, stable and ideal urea oxide (UOR) electrocatalyst is key to produce green hydrogen in an economical way. Herein, Ru doped three dimensional (3D) porous Ni₃N spheres, with tannic acid (TA) and urea as the carbon and nitrogen resources, is synthesized via hydrothermal and low-temperature treated process (Ru–Ni₃N@NC). The porous nanostructure of Ni₃N and the nickel foam provide abundant active sites and channel during catalytic process. Moreover, Ru doping and rich defects favor to boost the reaction kinetics by optimizing the adsorption/desorption or dissociation of intermediates and reactants. The above advantages enable Ru–Ni₃N@NC to have good bifunctional catalytic performance in alkaline media. Only 43 and 270 mV overpotentials are required for hydrogen evolution (HER) and oxygen evolution (OER) reactions to drive a current of 10 mA cm^?2. Moreover, it also showed good electrocatalytic performance in neutral and alkaline seawater electrolytes for HER with 134 mV to drive 10 mA cm^?2 and 83 mV to drive 100 mA cm^?2, respectively. Remarkably, the as-designed Ru–Ni₃N@NC also owns extraordinary catalytic activity and stability toward UOR. Moreover, using the synthesized Ru–Ni₃N@NC nanomaterial as the anode and cathode of urea assisted water decomposition, a small potential of 1.41 V was required to reach 10 mA cm^?2. It can also be powered by sustainable energy sources such as wind, solar and thermal energies. In order to make better use of the earth's abundant resources, this work provides a new way to develop multi-functional green electrocatalysts.     

Photocatalytic system with water soluble nickel complex of S,S′-bis(2-pyridylmethyl)-1,2-thioethane over CdS nanorods for hydrogen evolution from water under visible light

In this paper, we report a new nickel complex, [(bpte)NiCl₂] (bpte = S,S′-bis(2-pyridylmethyl)-1,2-thioethane) that can serve as a catalyst both for electrochemical and photochemical driven hydrogen production from water. As an electrocatalyst, [(bpte)NiCl₂] can electrocatalyze hydrogen generation from a neutral buffer with a turnover frequency (TOF) of 555.78 mol of hydrogen per mole of catalyst per hour (mol H₂/mol catalyst/h) at an overpotential (OP) of 837.6 mV. Together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H₂A) as a sacrificial electron donor, the nickel complex also can photocatalyze hydrogen evolution in heterogeneous environments and can work for 107 h. Under an optimal condition, the photocatalytic system can afford 24900 mol of H₂ per mole of catalyst during 83 h irradiation, with a TOF of 300H₂ per catalyst per hour. The average value of apparent quantum yield (AQY) is ～24% at 420 nm.     

An alkaline-acid asymmetric electrolyzer using NiCoP/CoP/Co3O4 multi-shell hollow nanoflakes as cathode and Ag as anode to realizing energy efficient production of hydrogen and shape controllable silver oxide

Large scale hydrogen generation by water electrolysis is severely impeded by the high cost of noble metal electrode materials and the kinetic-sluggish anodic oxygen evolution reaction (OER). Here we design a MOF-derived NiCoP/CoP/Co₃O₄ multi-shell hollow nanoflakes as a low-cost cathode electrocatalyst for hydrogen evolution reaction (HER), and replace the OER with more favorable silver oxidation reaction (AOR). The NiCoP/CoP/Co₃O₄ supported on carbon cloth (CC@NiCoP/CoP/Co₃O₄) endows an impressive low overpotential (η) of 90 mV at 10 mA cm⁻² and a low Tafel slope of 81.7 mV dec⁻¹ for HER in 0.5 M H₂SO₄ electrolyte. Coupling it with Ag electrode to forming an asymmetric alkali-acid electrolyzer exhibits superior performance with the requirement of a cell voltage of only 1.16 V to attain 10 mA cm⁻² with nearly 100% of Faradaic efficiencies for both H₂ and Ag₂O generation, showing dramatically lower voltage than that previously reported for conventional water splitting systems. In addition, the size and shape of Ag₂O can be controlled by manipulating current density. Our electrolyzer design provides not only an economical approach to produce H₂ and Ag₂O but also shows great promise for expansion into the electrosynthesis of other value-added chemicals.     

Facile construction of 3D hyperbranched PtRh nanoassemblies: A bifunctional electrocatalyst for hydrogen evolution and polyhydric alcohol oxidation reactions

Development of highly effective and stable electrocatalysts is urgent for various energy conversion applications. Herein, a facile co-reduction approach was developed to fabricate three-dimensional (3D) hyperbranched PtRh nanoassemblies (NAs) under solvothermal conditions, where creatinine and cetyltrimethylammonium chloride (CTAC) were employed as the structure-directing agents. The as-synthesized nanocatalyst exhibited intriguing catalytic characters for hydrogen evolution reduction (HER) with a low overpotential (20 mV) at 10 mA cm⁻² and a small Tafel slope (49.01 mV dec⁻¹). Meanwhile, the catalyst showed remarkably enlarged mass activity (MA: 2.16/2.02 A mg⁻¹) and specific activity (SA: 4.16/3.88 mA cm⁻²) towards ethylene glycol and glycerol oxidation reactions (EGOR and GOR) alternative to commercial Pt black and homemade Pt₃Rh nanodendrites (NDs), PtRh₃ NDs and Pt nanoparticles (NPs). This method offers a feasible platform to fabricate bifunctional, efficient, durable and cost-effective nanocatalysts with finely engineered structures and morphologies for renewable energy devices.     

In-situ surface selective removal: An efficient way to prepare water oxidation catalyst

The design of cost-efficient earth-abundant catalysts with superior performance for oxygen evolution reaction (OER) is extremely important for future renewable energy production. The synthesis of high-surface-area catalysts with high intrinsic activity remains challenging. In this work, in-situ surface selective removal method by electrochemical oxidation is used to synthesize nickel (oxy)hydroxide covered Ni₃Sn₂ supported on carbon nanotubes (Ni₃Sn₂@NiO_xH_y/CNT), which exhibits 10, 100, 200 and 300 mA cm⁻² at overpotential of 250, 317, 329 and 335 mV in OER, respectively. In-situ surface selective removal of Sn from the crystal lattices and oxidation of Ni under anodic oxidation provide highly active amorphous NiO_xH_y with abundant surface defects, leading to the high apparent activity (current density) and intrinsic activity (TOF) of the Ni₃Sn₂@NiO_xH_y/CNT. This work develops a general method to synthesize high-surface-area water oxidation catalysts, which can be used to prepare a series of catalysts for oxygen evolution reaction in the near future.     

MoS2-graphene-CuNi2S4 nanocomposite an efficient electrocatalyst for the hydrogen evolution reaction

We present a facile methodology for the synthesis of a novel 2D-MoS₂, graphene and CuNi₂S₄ (MoS₂-g-CuNi₂S₄) nanocomposite that displays highly efficient electrocatalytic activity towards the production of hydrogen. The intrinsic hydrogen evolution reaction (HER) activity of MoS₂ nanosheets was significantly enhanced by increasing the affinity of the active edge sites towards H⁺ adsorption using transition metal (Cu and Ni₂) dopants, whilst also increasing the edge sites exposure by anchoring them to a graphene framework. Detailed XPS analysis reveals a higher percentage of surface exposed S at 17.04%, of which 48.83% is metal bonded S (sulfide). The resultant MoS₂-g-CuNi₂S₄ nanocomposites are immobilized upon screen-printed electrodes (SPEs) and exhibit a HER onset potential and Tafel slope value of – 0.05 V (vs. RHE) and 29.3 mV dec⁻¹, respectively. These values are close to that of the polycrystalline Pt electrode (near zero potential (vs. RHE) and 21.0 mV dec⁻¹, respectively) and enhanced over a bare/unmodified SPE (– 0.43 V (vs. RHE) and 149.1 mV dec⁻¹, respectively). Given the efficient, HER activity displayed by the novel MoS₂-g-CuNi₂S₄/SPE electrochemical platform and the comparatively low associated cost of production for this nanocomposite, it has potential to be a cost-effective alternative to Pt within electrolyser technologies.