A 3d-4d-5d High Entropy Alloy as a Bifunctional Oxygen Catalyst for Robust Aqueous Zinc-Air Batteries.

The development of cost-effective catalysts for oxygen evolution and reduction reactions (OER/ORR) is essential for the commercialization of zinc-air batteries (ZABs). High entropy alloys (HEAs) are highly suitable candidates as they offer numerous parameters for optimizing the electronic structure and catalytic sites. Herein, FeCoNiMoW HEA nanoparticles are synthesized using a solution-based low-temperature approach. Such FeCoNiMoW nanoparticles show high entropy properties, subtle lattice distortions, and modulated electronic structure, leading to superior OER performance with an overpotential of 233 mV at 10 mA/cm and 276 mV at 100 mA/cm . Density functional theory (DFT) calculations reveal the electronic structures of the FeCoNiMoW active sites with an optimized d-band center position that enables suitable adsorption of OOH* intermediates, and reduces the Gibbs free energy barrier in the OER process. Aqueous ZABs based on this HEA demonstrate a high open circuit potential of 1.59 V, a peak power density of 116.9 mW/cm , a specific capacity of 857 mAh/g and excellent stability for over 660 h of continuous charge-discharge cycles. Flexible and solid ZABs are also assembled and tested, displaying excellent charge-discharge performance at different bending angles. This work shows the significance of 4d/5d metal-modulated electronic structure and optimized adsorption ability to improve the performance of OER/ORR, ZABs, and beyond. This article is protected by copyright. All rights reserved.