Recent advances in high entropy alloys for electrochemical water splitting: Materials, synthesis, and applications

High entropy alloys (HEAs) are a class of materials composed of more than one major element that enable the formation of homogeneous solid solution structures while preventing phase separation. Their unique properties, namely alloying effects, chemical disorder, lattice distortion, and cocktail effect, give them significant promise in catalysis and energy storage applications. In recent years, HEAs have attracted attention as functional materials for electrochemical water splitting, especially in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), due to their abundant active sites and high structural stability. Their electrochemical performance can be further enhanced by adding active transition metals such as Ni, Cr, or Fe. This study first reviews various synthesis techniques for HEAs, including hydrothermal synthesis, melt spinning, mechanical alloying, microwave sintering, electroplating, carbothermal shock synthesis, arc melting, and magnetron sputtering, and highlights their roles in tailoring the structural and surface properties of catalysts. It then analyzes the physicochemical properties of HEAs in detail, followed by a comprehensive discussion of their electrochemical behavior in HER and OER. Particular emphasis is placed on advanced strategies for the rational design of HEA-based electrocatalysts.