Co-Doped Ni3S2 Porous Nanocones as High-Performance Bifunctional Electrocatalysts in Water Splitting

Abstract Developing non-precious nickel-based catalysts with high activity and low cost is a big challenge for industrial alkaline water splitting. Herein, Co-doped Ni3S2 nanocones (Co12@Ni3S2/NF) are prepared by vulcanizing a cobalt oxide nanofilm on the porous nickel foam (NF) by atomic layer deposition (ALD). The electrocatalysts boast a large specific surface area, abundant active sites for rapid diffusion of electrolyte ions, fast electron transportation, and high electrochemical activity. Especially, the Co12@Ni3S2/NF electrode exhibits excellent catalytic reactivity such as a small overpotential of 62 mV to attain a current density of 10 mA cm−2 and Tafel slope of 49 mV dec−1 for HER as well as 297 mV versus RHE at 20 mA cm−2 and Tafel slope of 50.3 mV dec−1 for OER. First-principles calculations show that the proper Co dopant concentration in Ni3S2 causes large surface lattice distortion resulting in high effective ionic charge of Co atoms to greatly enhance water splitting. The strategy and materials provide insights into the design and preparation of efficient, low-cost, and durable electrodes in water splitting applications.