Unveiling the Mechanism of Fe-Doping-Enhanced Oxygen Evolution Reaction of CoSe

Abstract

Although iron doping is widely known to enhance the oxygen evolution reaction (OER) activity of transition metal-based catalysts, its role in triggering in-situ structural evolution remains poorly understood. Herein, we synthesize a Fe-doped CoSe catalyst and elucidate its activation mechanism.Under OER conditions, Fe doping weakens the Co-Se bond, thereby triggering the structural evolution of CoSe into highly active CoOOH and Co 3 O 4 . This process is accompanied by the insitu leaching and its sequential oxidation to selenate, together with the oxidation of Fe 3+ /Co 3+ to higher valence states. DFT calculations reveal that Fe incorporation effectively tunes the electronic structure of Co by shifting the d-band center toward the Fermi level. This electronic modulation optimizes the adsorption energetics of OER intermediates and lowers the energy barrier of the ratedetermining *OH → *O step. As a result, the FeCoSe only required an overpotential of only 265 mV to achieve a current density of 10 mA cm⁻ 2 with a relatively low Tafel slope of 57.3 mV dec⁻ 1 . Moreover, anion exchange membrane water electrolysis (AEMWE) assembled with the FeCoSe//Pt/C acquired a current density of 100 mA cm -2 at a voltage of 1.5 V, which is better than that of RuO 2 //Pt/C (1.65 V), highlighting its potential for practical implementation.