Identifying the intrinsic active site in bimetallic Co3S4/Ni3S2 feathers on MXene nanosheets as a heterostructure for efficient oxygen evolution reaction

Abstract

Exploring economical, efficient and stable electrocatalysts toward the oxygen evolution reaction (OER) is crucial for the advancement of water splitting to optimize sustainable energy conversion technologies. Herein, Co₃S₄/Ni₃S₂ feathers are fixed on MXene nanosheets supported by nickel foam as a NF@MXene@Co₃S₄/Ni₃S₂ heterogeneous electrocatalyst through hydrothermal reaction. The catalyst exhibits excellent OER performance in alkaline medium (1M KOH) with a low overpotential of 186 mV at the current density of 10 mA cm⁻² and a small Tafel slope of 97 mV dec⁻¹, showing long-term durability over 24 h and good stability after 1000 cyclic voltammetry (CV) cycles. Theoretical calculation further identified that the key intrinsic active catalytic site in this bimetallic catalyst is the nickel atom of Ni₃S₂, which enables adsorption of the intermediates, due to a lower Gibbs free energy change of the rate-determining step of *O to *OOH. The effective identification of the intrinsic catalytically active site in the heterostructure contributes to the regulation of composites and the development of electrocatalysis applications in the OER.