Novel Ru‐O 3 Se 4 Single Atoms Regulate the Charge Redistribution at Ni 3 Se 2 /FeSe 2 Interface for Improved Overall Water Splitting in Alkaline Media

Abstract Developing low‐cost, highly active, and stable bifunctional catalysts is of great significance for electrochemical water splitting. Herein, novel Ru‐O 3 Se 4 single atoms doped Ni 3 Se 2 /FeSe 2 interface catalyst is fabricated by a two‐step method for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Notably, Ru‐Ni 3 Se 2 /FeSe 2 nanosheets exhibit excellent HER (43 mV@10 mA cm −2 ) and OER (283 mV@100 mA cm −2 ) activities in alkaline solution. In particular, the mass activity of Ru‐Ni 3 Se 2 /FeSe 2 catalyst is 3593.61 mA mg Ru −1 at 200 mV for HER and 7073.80 mA mg Ru −1 at 400 mV for OER, which is 25.91 and 367.28 times of commercial Pt/C and RuO 2 , respectively. In situ spectroscopy techniques confirm Ru‐O 3 Se 4 single atoms facilitate the adsorption of intermediates H * and OOH * during HER and OER processes, respectively. Further density functional theory calculations reveal introducing Ru‐O 3 Se 4 single atoms causes the transfer of electrons from Ru to Ni and Fe atoms, leading to a redistribution of charge at the Ni 3 Se 2 /FeSe 2 interface, thus reducing the energy barriers of rate‐determining step to −0.37 and 1.92 eV for HER and OER, respectively. This work emphasizes the significant role of single atoms at the interface for overall water splitting.