Transition-metal alloy electrocatalysts with active sites modulated by metal-carbide heterophases for efficient oxygen evolution

Given oxygen evolution reaction as the rate-limiting step for electrocatalytic water splitting, it is essential to accelerate water oxidation kinetics by modulating the population and intrinsic activity of active sites. Herein, by annealing the mixture of Fe, Ni, and Mo precursors, FeNi alloys compositing with Mo₂C heterophases supported on carbon layers (FeNi–Mo₂C/C) were synthesized and exhibited a promising activity for oxygen evolution, with a small overpotential of 288 mV at 10 mA cm^-2, which is even superior to the benchmark noble metal-based catalyst (e.g., RuO₂). The introduced Mo₂C heterophases reduced the particle size of FeNi alloys, increasing the amount of surface electrocatalytically active sites, and tuned the electronic structures of FeNi alloys, stimulating the surface phase transformation with highly-active metal oxides formed for the enhanced intrinsic activity of active sites. This work presents an effective and alternative approach to the modulation of electrocatalytic active sites for electrochemical energy applications.