High-Entropy Alloy\nwith Mo-Coordination as Efficient\nElectrocatalyst for Oxygen Evolution Reaction

Abstract

Electrochemical hydrolytic hydrogen production is the\nmost promising\nmethod for renewable energy storage and conversion. However, the kinetic\nslow oxygen evolution reaction (OER) limits the development of water\nelectrolysis at the anode. The state-of-the-art OER catalysts face\na dilemma of high content of noble metals and low OER activities.\nHerein, a strategy for achieving efficient and stable high-entropy\nalloy (HEA) catalysts by Mo-coordination is reported. The earth-abundant\nFeCoNiMo HEA catalyst provides an overpotential as low as 250 mV at\nthe current density of 10 mA cm^–2 in alkaline medium,\nwhich is 89 mV lower than that of state-of-the-art IrO₂. The turnover frequency of 0.051 s^–1 at the overpotential\nof 300 mV of FeCoNiMo HEA is 3 times higher than that of commercial\nIrO₂ catalyst and even 11 times higher than that of the\nFeCoNi alloy without Mo-coordination. Importantly, the FeCoNiMo HEA\nexhibits high OER stability at a high current density of 100 mA cm^–2. Methanol molecular probe experiment and X-ray photoelectron\nspectroscopy analyses suggest that the electrons of Mo transfer to\nFe, Co, and Ni in the FeCoNiMo HEA catalyst, which leads to a weakened\nOH* bonding and, as a result, enhanced OER performance of the FeCoNiMo\nHEA catalyst. Consistent with the methanol molecular probe analysis,\nthe real-time OER kinetic simulation reveals that the coordination\nof Mo within FeCoNi can speed up the rate-determining OH* deprotonation\nstep of OER. Our finding opens up a routine for designing efficient\ncost-effective electrocatalysts for OER, which could facilitate discoveries\nin OER catalysts.