Surface treated nickel phosphide nanosheet with oxygen as highly efficient bifunctional electrocatalysts for overall water splitting

The development of high catalytic activity, earth-abundant, low-cost, and long-term stability electrocatalysts is highly desirable. In this study, oxygen surface treated Ni₂P nanosheets as bifunctional catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is proposed based on density functional theory calculations. The mechanism of the enhanced electrocatalytic performance was investigated by considering oxygen adsorption and substitution of surface phosphorus on the Ni₂P nanosheets surface. The results show that six O adsorption and six O substitution Ni₂P exhibit excellent electrocatalytic performance because of their tuned Gibbs free energy and overpotential for hydrogen/oxygen evolution reaction being just −0.21 eV/0.27 V and − 0.15 eV/0.45 V, respectively. Additionally, due to the reducing of total potential, the catalysts can present better OER performance in alkaline media. The bicatalytic activities of O adsorption and O substitution can be well-explained by an amendatory p band-center model, which is also suitable for a broad class of surface engineering systems. This theoretical study not only provides vital insights into the enhanced mechanism of the bifunctional activities of water splitting but also helps to prescribe the principles for designing high performance multifunctional electrocatalysts.