Hierarchically three-level Ni3(VO4)2@NiCo2O4 nanostructure based on nickel foam towards highly efficient alkaline hydrogen evolution

Designing mixed transition metal oxides with advantageous nanostructure is efficient access to highly-efficient electrocatalysts for hydrogen evolution reaction (HER) in water electrolysis due to more exposed active sites and synergistic effects in mixed metals. A hierarchically three-level nanostructure combining two types of mixed transition metal oxides on nickel foam (Ni-3(VO4)(2)@NiCo2O4/NF) has been synthesized through a two-step hydrothermal process. The hierarchically three level nanostructure comprises porous nickel foam as robust and conductive substrate in the bottom, vertical and uniform NiCo2O4 nanowires arrays in the intermediate, and top-coated Ni-3(VO4)(2) nanoparticles in 10 nm. The triple hierarchical nanostructure of Ni-3(VO4)(2)@NiCo2O4/NF is favorable for enlarging surface areas, exposing more active sites, promoting mass and charge transfer and accelerating HER process. Ni-3(VO4)(2)@NiCo2O4/NF electrode can afford a current density of 10 mA cm(-2) at a moderate overpotential of 113 mV with robust stability for at least 12 h. It may provide a new strategy to design triple hierarchical nanostructures based on earth-abundant transition metals to achieve large-scale production of hydrogen through water electrolysis in alkaline. (C) 2017 Elsevier Ltd. All rights reserved.