Synergistically Integrating Nickel Porous Nanosheets with 5d Transition Metal Oxides Enabling Efficient Electrocatalytic Overall Water Splitting

An integration hydrogen adsorption benign component such as a metal with an oxygen-containing reactant adsorption benign component such as metal oxide allows for efficient overall water splitting in alkaline solutions and yet remains a considerable challenge. Herein, 5d transition metal oxide WO2 and WO3 (denoted as WOx) nanoparticles are purposely integrated with a porous Ni nanosheet array grown on nickel foam (NF) to design a strongly coupled Ni/WOx/NF porous nanosheet array electrocatalyst. Through the anion exchange of Ni(OH)2 nanosheets with tungstate, followed by hydrogenation treatment, abundant Ni/WOx interfaces with strong coupling interaction are generated. Benefiting from the strong synergies between Ni and WOx and the unique nanostructure, Ni/WOx/NF only requires the overpotentials of 42 mV for hydrogen evolution reaction (HER) and 395.7 mV for oxygen evolution reaction (OER) to achieve the current densities of 10 and 100 mA cm–2, respectively. Furthermore, the Ni/WOx/NF can achieve a current density of 10 mA cm–2 at a low cell voltage of 1.54 V in a two-electrode system. This work opens a novel avenue for the design of high-performance but low-cost electrocatalysts for overall water splitting.