Anion Engineering on 3D Ni₃S₂ Nanosheets Array toward Water Splitting

Anion engineering on transition-metal-based materials has been put forward as an important strategy to develop efficient and stable non-noble-metal electrocatalysts toward water electrolysis, including both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). On the basis of theoretical predictions, a three-dimensional (3D) integrated electrode constructed by P-decorated Ni3S2 nanosheet arrays (Ni3S2|P) was prepared via a facile two-step method. The suitable controlled incorporation of P anions into the Ni3S2 matrix can have little influence on the crystal structure, and meanwhile can effectively modify the electronic structure, increase the concentration of charge carrier, supply more delocalized electrons, facilitate more active sites to be electrically activated, optimize the hydrogen adsorption Gibbs free energy, strengthen the interaction for water molecules, and benefit the oxidation of Ni2+ to Ni3+ oxo-/hydroxides. As a result, the freshly achieved 3D Ni3S2|P electrode exhibits higher activity with lower overpotential toward HER and OER, in comparison with its pristine counterpart. Furthermore, when employed in an overall electrolytic cell as both cathode and anode, it can reduce the required overvoltage of 100 mV for reaching 10 mA cm–2 current density, verifying the great potential of anion engineering in the design of bifunctional materials for overall water splitting.