Novel Ru-O3Se4 Single Atoms Regulate the Charge Redistribution at Ni3Se2/FeSe2 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-O₃Se₄ single atoms doped Ni₃Se₂/FeSe₂ interface catalyst is fabricated by a two-step method for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Notably, Ru-Ni₃Se₂/FeSe₂ 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-Ni₃Se₂/FeSe₂ 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 RuO₂, respectively. In situ spectroscopy techniques confirm Ru-O₃Se₄ single atoms facilitate the adsorption of intermediates H^* and OOH^* during HER and OER processes, respectively. Further density functional theory calculations reveal introducing Ru-O₃Se₄ single atoms causes the transfer of electrons from Ru to Ni and Fe atoms, leading to a redistribution of charge at the Ni₃Se₂/FeSe₂ 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.