Mo-Doped Ni₃S₂ Nanosheet Arrays for Overall Water Splitting

Abstract

Designing effective and low-cost bifunctional electrocatalysts for the alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential to achieve green development of the hydrogen economy. Herein, we have developed Mo-doped Ni3S2 nanosheet array catalysts with excellent electrochemical properties. Only 85 mV (HER) and 230 mV (OER) overpotentials are required under alkaline conditions at 10 mA cm–2 and remain undegraded for 100 h. In addition, it only required 1.52 V at 10 mA cm–2 in an alkaline electrolyzer, and it remained unchanged for more than 100 h in stability tests, outperforming most reported electrocatalysts. Experiments and density functional theory (DFT) calculations confirmed that the doping of Mo could expose more active sites of Ni3S2 and optimize the adsorption free energy of the intermediate, which in turn improves its intrinsic activity. This work reveals the key role of Mo in Ni3S2 electrocatalytic performance enhancement at the atomic scale.