High-entropy alloys: Atomic horizons for sustainable electrocatalytic reactions

High-entropy alloy (HEA) materials have been considered as promising materials for electrocatalytic reactions, including O₂, CO₂, N₂ and NO₃⁻ reduction reactions (ORR, CO₂RR, NRR, and NO₃⁻RR), and O₂ and H₂ evolution reactions (OER and HER), due to their distinctive compositions, driving exceptional stability and performance through four key phenomena—high entropy, sluggish diffusion, severe lattice distortion, and the cocktail effect. These phenomena synergistically enhance the properties of HEA materials. Despite their impressive potential in electrocatalysis, HEAs face significant hurdles, including limited insight into their long-term stability, challenges in property optimization, complex microstructures, and issues with manufacturing consistency, cost, and scalability, all of which hinder their full integration at practical level. Therefore, to unlock the full potential of HEAs, a comprehensive and rigorous quantitative assessment is imperative. This evaluation must delve into the core scientific and engineering principles of HEAs, exploring their physico-chemical and electrochemical properties, addressing inherent challenges, and identifying key future prospects for their advancement. In response to this demand, this review is meticulously crafted to unveil the fundamental principles, phase structures, synthesis techniques, and key characteristics of these materials. It offers an in-depth exploration of the scientific mechanisms underlying HEA formation and the engineering strategies employed to optimize their properties. Additionally, this review critically examines both experimental and theoretical progress, highlighting the promising performance of HEAs in electrocatalysis. The challenges inherent to HEA engineering, characterization, and electrochemical performance are thoroughly assessed while providing a forward-looking perspective on their future development. This comprehensive analysis is intended to serve as a valuable resource for new readers, academicians, researchers, and industry professionals.