Interface engineering of metallic nickel nanoparticles/semiconductive nickel molybdate nanowires for efficiently electrocatalytic water splitting

Constructing heterointerface is an efficient strategy to enhance the catalytic activity for various electrochemical reactions. Herein, metallic nickel nanoparticles (NPs)/semiconductive nickel molybdate nanowires (NWs) (Ni/Ni2Mo3O8/CC) are constructed for overall water splitting. Experiment results show that the electrons can transfer from metallic Ni to semiconductive Ni2Mo3O8 through the NP/NW interfaces due to the heterojunction effect, endowing Ni2Mo3O8 and Ni with significantly enhanced activities for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Density functional theory (DFT) calculations demonstrate that the synergistic effect between metallic Ni and Ni2Mo3O8 not only increases the electrical conductivity of the Ni2Mo3O8 but also optimizes adsorption energies of hydrogen (ΔGH∗) and water (ΔEH2O), effectively improving the HER and OER activities in alkaline electrolyte. To drive a current density of 10 mA cm−2 in alkaline electrolyte, the Ni/Ni2Mo3O8/CC only needs 47 and 208 mV overpotentials for HER and OER, respectively, much lower than most of the reported non-noble metal-based electrocatalysts. Importantly, a two-electrode electrolyzer using Ni/Ni2Mo3O8/CC as bifunctional catalysts only needs a cell voltage of 1.51 V to get 10 mA cm−2, superior to the benchmark Pt/C and IrO2 couple. Our findings provide a promising way for the design of heterojunction-based materials for water electrolysis.