Deciphering the Dynamic Structure Evolution of Fe- and Ni-Codoped CoS₂ for Enhanced Water Oxidation

Multimetal doping is a promising strategy to achieve high-performance electrocatalysts for the oxygen evolution reaction (OER) due to synergistic effects; however, understanding the dynamic structure evolution and clarifying the catalytic mechanism of each individual doping metal in multimetal-based electrocatalysts remain elusive. Here, we report the synthesis of homogeneous single-metal and bimetal doping sulfides with a pyrite structure for OER catalysts via a high-pressure and high-temperature (HPHT) technique; operando Raman and X-ray absorption spectroscopy (XAS) studies are performed to capture the dynamic evolution during the OER process. Our results find that an Fe- and Ni-codoped CoS₂ electrocatalyst exhibits significantly improved OER activity with an overpotential of 242 (295) mV at 10 (100) mA cm^–2 and robust stability over 500 h in an alkaline medium. Operando analysis reveals that Fe and Ni incorporations not only expedite the dynamic response of self-reconstructions of the Fe,Ni-CoS₂ surface but also accelerate the oxidation of Co and Fe into high-valence oxyhydroxides while suppressing nickel oxidation to form Ni­(OH)₂ for optimized activity and robust stability. This finding provides a fundamental understanding of the composition design, dynamic reaction pathways, and controlling principle for highly active multimetal-based OER catalysts.