High-entropy alloy electrocatalysts for oxygen reduction and hydrogen evolution reactions: Recent advances and future perspectives

Abstract

The growing demand for sustainable energy conversion underscores the need for efficient electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells and metal–air batteries, and for the hydrogen evolution reaction (HER) in water electrolysis. High-entropy alloys (HEAs), enabled by multi-principal-element design and high-entropy “core effects”, offer a promising alternative to costly noble-metal catalysts by combining tunable electronic structures, multi-site/ensemble effects, and potentially improved durability. This review summarizes recent progress in HEA electrocatalysts for the ORR and HER. We discuss reaction mechanisms and key activity/stability metrics in acidic and alkaline media and provide bibliometric insights highlighting the rapid growth of the field and the prevalence of 3d-transition-metal-rich compositions. Reported catalyst performances are further organized by composition dominance (3d/4d/5d transition metals) and linked to electronic-structure considerations, alongside an overview of representative synthetic strategies. Finally, we outline the remaining challenges and provide an outlook toward practical electrochemical applications.