Rare-Earth-Metal-Tuned Local Electronic Structure of High-Entropy Alloys for Ampere-Level Electrochemical Overall Water Splitting

Developing and creating multicomponent materials for alkaline water electrolysis at industrial-grade current density is a promising avenue to eco-friendly carbon-neutral energy systems, which remains challenging. Herein, a facile one-step electrodeposition strategy for synthesizing efficient high-entropy alloys (HEAs) with a rare-earth-metal-tuned local electronic structure and a prominent multimetal synergistic effect for electrochemical overall water splitting is reported. The strong electron-donating ability of rare-earth metals, especially La elements in HEAs, facilitates the transfer of large numbers of electrons to heteroatoms, further regulates the adsorption of small reactant molecules, and enhances the chemical conversions. The engineered FeCoNiLaPd achieves an exceptional efficiency for electrochemical oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline conditions with overpotentials of 279 and 278 mV at a current density of 100 mA cm–2, respectively, as well as notable stability for both over 900 h under high current density. Only 382 mV of overpotential can be obtained on the versatile FeCoNiLaPd-driven OER at an ampere-level current density. Moreover, in-depth insights into the catalyst microstructure, electronic interactions, active sites, structure–activity relationships, key intermediates, and a four-step proton-coupled electron transfer deoxidation process involving the rate-determining step of *O to *OOH are comprehensively investigated.