Dual Vacancies Confined in Nickel Phosphosulfide Nanosheets Enabling Robust Overall Water Splitting

Exploring highly efficient electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for addressing energy and environmental crises. Vacancy engineering has been regarded as a promising way to optimize the catalytic activity of electrocatalysts. Herein, we put forward a conceptually new dual Ni,S vacancy engineering on 2D NiPS₃ nanosheet (denoted as V-NiPS₃ ) by a simple ball-milling treatment with ultrasonication. This material presents an ideal model for exploring the role of dual vacancies in improving the catalytic activity for overall water splitting. Structural analyses make clear that the formation of dual Ni,S vacancies regulates the electronic structure and catalytic active sites of NiPS₃ nanosheet, leading to the superior HER/OER performance. Smaller overpotentials of 124 mV and 290 mV can be achieved at a current density of 10 mA cm^-2 for HER and OER, respectively. The OER performance of V-NiPS₃ is the best value among all state-of-the-art NiPS₃ catalysts. In addition, the assembled two-electrode cell incorporating V-NiPS₃ exhibits enhanced catalytic performance with a low cell voltage of 1.60 V at 10 mA cm^-2 . This work offers a promising avenue to improve the electrocatalytic performance of the catalysts by engineering dual vacancies for large-scale water splitting.