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Vertically aligned two-dimensional ReSe 2 are directly grown on conductive substrates by a chemical vapor deposition method for enhanced electrocatalytic hydrogen production. Two-dimensional electrocatalysts with high-density active sites together with a good charge transfer to the conductive substrates can improve their hydrogen evolution reaction performances. Typically, a good contact between catalyst and electrode to enhance charge transfer can be achieved by way of direct growth. However, a controllable growth of vertically aligned two-dimensional ReSe 2 directly on conductive substrates as working electrodes is not reported. In this work, for the first time, vertically aligned ReSe 2 nanosheets directly on conductive substrates (carbon cloth and glass carbon) are realized though a controllable chemical vapor deposition method. Compare to the way of transferring two-dimension ReSe 2 , the electrode with optimized growth of two-dimensional ReSe 2 exhibits superior hydrogen evolution reaction performances. [ABSTRACT FROM AUTHOR]

[Display omitted] Construction of heterogeneous interfaces with dual active components to synergistically promote both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an effective strategy for facilitating electrochemical water splitting, but the appropriate active component regulation via simple synthesis procedures is still challenging. Herein, the Co and Co 2 Mo 3 O 8 active components are screened to construct effective heterogeneous interfaces and successfully integrated on Ni foam by thermal reduction of cobalt molybdate precursor. And this bifunctional electrode (Co/Co 2 Mo 3 O 8 /NF) required overpotentials of only 164 and 360 mV to drive the 100 mA cm−2 for HER and OER in alkaline media, respectively. Theoretical calculations showed that the electron transfer occurred from Co to Co 2 Mo 3 O 8 at the interface, then the formed interfacial cobalt atoms with deficient electron were beneficial for water activation, and reduced energy barrier of water dissociation under the synergistic effect of Co 2 Mo 3 O 8. Notably, the alkaline electrolyzer based on symmetric Co/Co 2 Mo 3 O 8 /NF electrodes generated 100 mA cm−2 at a voltage of only 1.75 V, surpassing commercially available precious-metal Pt/RuO 2 -based catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Hydrogen energy is expected to replace fossil fuels as a mainstream energy source in the future. Currently, hydrogen production via water electrolysis yields high hydrogen purity with easy operation and without producing polluting side products. Presently, platinum group metals and their oxides are the most effective catalysts for water splitting; however, their low abundance and high cost hinder large-scale hydrogen production, especially in alkaline and neutral media. Therefore, the development of high-efficiency, durable, and low-cost electrocatalysts is crucial to improving the overpotential and lowering the electrical energy consumption. As a solution, Ni 2 P has attracted particular attention, owing to its desirable electrical conductivity, high corrosion resistance, and remarkable catalytic activity for overall water splitting, and thus, is a promising substitute for platinum-group catalysts. However, the catalytic performance and durability of raw Ni 2 P are still inferior to those of noble metal-based catalysts. Heteroatom doping is a universal strategy for enhancing the performance of Ni 2 P for water electrolysis over a wide pH range, because the electronic structure and crystal structure of the catalyst can be modulated, and the adsorption energy of the reaction intermediates can be adjusted via doping, thus optimizing the reaction performance. In this review, first, the reaction mechanisms of water electrolysis, including the cathodic hydrogen evolution reaction and anodic oxygen evolution reaction, are briefly introduced. Then, progress into heteroatom-doped nickel phosphide research in recent years is assessed, and a discussion of each representative work is given. Finally, the opportunities and challenges for developing advanced Ni 2 P based electrocatalysts are proposed and discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] Enhancing double-phase mass transfer capability and reducing overpotential at high currents are critical in the oxygen evolution reaction (OER) catalyst design. In this work, nickel–iron layered double hydroxide (NiFe-LDH) loaded on nickel foam (NF) was used as a self-sacrificing template for subsequent growth of nickel–iron Prussian blue (NiFe-PBA) hollow nanocubes on its sheet arrays. The triple-scale porous structure is therefore in -situ constructed in the produced NiFe-PBA@LDH/NF catalyst, where NiFe-PBA nanocubes, NiFe-LDH sheets and NF skeletons provide pores at hundred-nanometers, microns and hundred-microns, respectively. Due to the successful construction of hierarchical mass transfer channels in the catalyst, the overpotential required to deliver 1000 mA cm−2 OER is only 396 mV, which is 80 mV lower than that of NiFe-LDH/NF with a double-scale porous structure, manifesting the importance of the appropriate mass transfer channels, promoting the potential application of the NiFe-PBA@LDH/NF catalyst in industrial-scale electrolysers. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We successfully synthesized sea urchin-like ternary cobalt phosphosulfide (CoPS). • CoPS is a high-efficiency bifunctional electrocatalyst for overall water splitting. • DFT calculations reveal the mechanism that CoPS has favorable performance for OER and HER. Abstract The development of efficient non-noble bifunctional electrocatalysts for the overall water splitting is a pressing and challenging task. In this work, we report a sea urchin-like cobalt phosphosulfide (CoPS) ternary compound for overall water splitting. Because CoPS contains more than one nonmetallic element, ternary compounds possess dianions might lead to modulated electronic structure and thus modified their electrocatalytic properties. Our DFT calculation results reveal that the ternary CoPS exhibits favorable performance for both the oxygen evolution reaction and hydrogen evolution reaction. Experimentally set as cathode and anode in a full cell for overall water splitting, the CoPS cell needs a voltage of only ∼1.59 V to reach a current density of 10 mA cm−2 and has outstanding stability. Our results open up a path to search for alternative bifunctional electrocatalyst materials to substitute for noble metals in overall water splitting. [ABSTRACT FROM AUTHOR]

Ni/Mo 2 C hetero-sheet arrays are grown vertically on nickel foam skeleton to utilize the advantages of Ni and Mo 2 C on promotion of HER kinetics and 3D structure on mass transfer and accessibility and only 151 and 271 mV overpotentials are needed to deliver 100 and 1000 mA/cm2 HER, respectively. [Display omitted] • Ni-doped Mo 2 C nanosheet arrays are grown vertically on nickel foam skeleton. • Polyvinylpyrrolidone is used as soft template for catalyst preparation. • 151 and 271 mV overpotentials are needed to deliver 100 and 1000 mA/cm2 HER. • The HER can stably operate for more than 500 h. Practical structural design and electronic regulation are significant for synthesising efficient electrocatalysts. Therefore, a facile soft-template approach has been applied to successfully grow Ni/Mo 2 C heterojunction nanosheet arrays on nickel foam (NF) skeleton (NS-Ni/Mo 2 C@NF) using polyvinylpyrrolidone (PVP) as a soft template. The density functional theory (DFT) calculations reveal that abundant Ni/Mo 2 C heterojunction in NS-Ni/Mo 2 C@NF can provide many active sites with a moderate hydrogen adsorption free energy (ΔG H* , 0.037 eV). Benefiting from this nanosheet array structure and abundant Ni/Mo 2 C heterojunctions, the NS-Ni/Mo 2 C@NF catalyst can efficiently catalyze HER, especially at large current densities. As a result, only 151 and 271 mV overpotentials are needed to deliver 100 and 1000 mA/cm2 HER, respectively. More importantly, the hydrogen production testing with NS-Ni/Mo 2 C@NF as the working electrode can run stably for 500 h without activity decay under the current density of 500 mA/cm2 commonly used in industrial water electrolyzers, indicating that NS-Ni/Mo 2 C@NF has broad application prospects. [ABSTRACT FROM AUTHOR]

Self-confinement synthesized Ni@Mo 2 C/CN can stalely achieve 10 mA/cm2 overall urea oxidation with 1.51 V applied voltage due to the mutual promotion effect of Ni and Mo 2 C on UOR activity and HER activity. [Display omitted] • Ni@Mo 2 C/CN catalyst was synthesized via an in situ self-confinement strategy. • A mutual promotion effect of Ni and Mo 2 C on UOR activity and HER activity exists. • An applied voltage of 1.51 V can achieve 10 m A/cm2 stable overall urea oxidation. Efficient hydrogen production from water splitting is crucial for sustainable energy and yet impeded by sluggish anodic water oxidation. Urea oxidation had been considered as an alternative reaction due to its much lower oxidation potential. Rational design of highly efficient cost-effective electrocatalysts for urea oxidation is therefore urgent for hydrogen production from overall urea oxidation. Here, the Ni/Mo 2 C@CN catalyst consisting of a porous carbon shell and a heterojunction Ni/Mo 2 C core was constructed by an in situ self-confinement synthesis strategy. The mutual promotion effect of Ni and Mo 2 C can boost the urea oxidation and hydrogen evolution reactions at the same time. Only 1.51 V applied potential was needed to achieve stable 10 mA/cm2 overall urea oxidation on the Ni/Mo 2 C@CN catalyst. By considering the great stability resulting from the protective effect of the carbon shell, a practical application potential of Ni/Mo 2 C@CN in overall urea oxidation was achieved. [ABSTRACT FROM AUTHOR]