Electrodeposited high-entropy alloys as electrocatalysts in water electrolysis for hydrogen production: a review on impacts of composition and synthesis parameters

Abstract High-entropy alloys are described as materials that have equiatomic and multi-element compositions. Their unique atomic structure may provide alternative electrocatalysts for water electrolysis over traditional and expensive noble metal-based catalysts, delivering superior catalytic activity and stability. Among various high-entropy alloys synthesis methods, electrodeposition stands out as a versatile and cost-effective approach due to its mild conditions and precise control over composition and deposition properties. This review focuses on noble metalfree high-entropy alloys prepared by electrodeposition, with applications in water electrolysis. The impacts of alloying elements and electrodeposition parameters on the morphology, composition, and electrochemical performance of the resulting coatings for hydrogen evolution reaction and oxygen evolution reaction are also examined. The roles of key alloying elements are discussed, including their individual contributions during the electrodeposition process, interactions within the bath, and effects on the final coating. The review also discusses critical deposition parameters such as bath chemistry, pH value, current density, temperature, and bath agitation, and their influences on properties and electrochemical activity of electrodeposited coatings. Finally, future research directions and recommendations in several key areas are outlined to address important knowledge gaps for further advancing the optimization and application of electrode-posited high-entropy alloys as effective electrocatalysts for water electrolysis.