Atomic-scale engineering of bimetallic sites via cobalt-mediated reconstruction for enhanced water electrolysis

The development of efficient oxygen evolution reaction (OER) electrocatalysts requires precise regulation of atomic-scale active sites to overcome the inherent limitations of conventional NiFeOOH materials, where the conflicting adsorption strengths at Ni and Fe sites restrict intermediate optimization. In this study, we develop a self-reconstruction strategy utilizing FeCoNi(S)/NiFe foam (NFF) precursors to synthesize structurally optimized FeCoNiOOH/NFF electrocatalysts. The cobalt-mediated reconstruction process enables partial substitution of Ni sites, resulting in enhanced intermediate adsorption energy on Ni sites. Density functional theory (DFT) calculations reveal that Co-doping atomically modulates Ni coordination environments, elevating Ni valence to boost adsorption energetics. This structural tailoring optimizes oxygen intermediates (*OOH/*OH, * denotes the adsorbed species on the catalyst surface) binding via free energy regulation and charge redistribution-induced d-band upshifting, synergistically reducing the activation barrier of OER's rate-determining step. FeCoNi(S)/NFF demonstrates an outstanding electrochemical performance of 332 mV at a current density of 100 mA cm−2 and excellent stability over 350 h at 200 mA cm−2 with a ∼ 98% potential retention. This work provides mechanistic insight into electrocatalysis enhancement through charge distribution-mediated structure-activity mechanisms and offers insight into the atomic-scale regulation of transition metal sulfides on high-performance catalysts for water electrolysis toward oxygen production.