High-Entropy Alloy with Mo-Coordination as Efficient Electrocatalyst for Oxygen Evolution Reaction

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

Automated summary

This study reports a strategy for achieving efficient and stable high-entropy alloy (HEA) catalysts with molybdenum coordination, which can be used for electrochemical hydrolytic hydrogen production. The HEA catalyst exhibits low overpotential, high turnover frequency, and high OER stability in alkaline medium. Methanol molecular probe experiment and kinetic simulation results support the effectiveness of this strategy.