A comprehensive review of high entropy oxides electrocatalysts: Advances, challenges, and prospects

High-entropy oxides (HEOs) have emerged as a groundbreaking class of materials in electrocatalysis, offering unparalleled compositional flexibility, synergistic multi-element effects, and exceptional stability. This review comprehensively explores the recent advances in HEOs, focusing on their unique properties, synthesis strategies, and electrocatalytic applications. We delve into the fundamental principles of HEOs, including high-entropy effects, lattice distortion, and cocktail effects, which underpin enhanced catalytic performance. Advanced synthetic methods, such as solid-state, liquid-phase, and gas-phase techniques, were systematically analyzed to customize the morphology, crystallinity, and active sites of hydroxide ions. Furthermore, we highlight the applications of HEOs in critical electrochemical reactions, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO₂RR), and other emerging catalytic reactions, emphasizing their superior activity and durability over conventional catalysts. Density functional theory (DFT) insights into active site modulation and reaction mechanisms are integrated to bridge experimental observations with theoretical understanding. Finally, we address current challenges and propose future directions for optimizing HEOs. This review aims to inspire innovative strategies for developing next-generation HEO-based electrocatalysts to meet global energy and sustainability demands.