Revealing the Surface Reconstruction on the High OER Catalytic Activity of Ni 3 S 2

Abstract Sluggish oxygen evolution reaction (OER) is a crucial part of water splitting and solar fuel generation, which limits their utilization. Ni 3 S 2 is a promising OER catalyst, in which surface reconstruction is an important step to improve performance. In this study, DFT calculations were employed to investigate the effect of surface reconstruction on (001), (110), and (101) surfaces of Ni 3 S 2 in alkaline OER. According to the Pourbaix diagram and surface free energy landscape, Ni 3 S 2 is prone to transform into Ni oxides and (oxy) hydroxides under alkaline OER conditions. This process induces exposed S atoms to leach and O from the electrolyte to incorporate S sites, thereby lowering the Bader charge of *O and increasing , and then decrease , the free energy penalty of the potential determining step. In general, the surface reconstruction enhances the OER activity through S leaching and adjusting the coordination environment. We believe this work not only provides insights into the clarification of surface reconstruction, but also provides a valuable guideline for the further discovery of efficient TM‐based sulfides.