Review on surface reconstruction in high-entropy electrocatalysts

Abstract High-entropy materials have emerged as a versatile platform for electrocatalysis because their multicomponent nature enables broad tunability of electronic structure, adsorption energetics, lattice distortion, defect chemistry, and chemical functionality. This compositional diversity opens access to a vast space of possible catalytic surfaces and local atomic environments, creating opportunities to optimize activity, selectivity, and durability beyond what is typically accessible in simpler mono-, binary, or ternary systems. At the same time, the very complexity that makes these materials attractive also makes them much more difficult to optimize and understand. The challenge is not only that the compositional space expands dramatically, making identification of the most effective composition intrinsically difficult, but also that mechanistic interpretation becomes substantially more complex. In particular, the mismatch between pre-catalyst and real catalyst, already a general issue in electrocatalysis, becomes especially difficult to identify and interpret in high-entropy systems because the number of plausible local atomic environments is vastly larger. This review examines the mechanisms of surface reconstruction in high-entropy electrocatalysts, analyzes how high-entropy compositions influence these pathways, reviews the experimental and computational approaches used to identify active states, and discusses strategies to control surface organization and active-state evolution. In doing so, it aims to provide a framework for designing high-entropy electrocatalysts with controllable and reaction-relevant active states.