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[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]

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]