Electrochemically Induced Structural Evolution to Generate Optimized High‐Entropy‐Alloy Electrocatalysts for Ethanol Oxidation

High‐entropy‐alloy (HEA) nanocrystals offer tremendous potential as next‐generation catalysts for complex electrochemical reactions. Nonetheless, there is a relative dearth of attention regarding the structural evolution of HEAs under electrochemical conditions. We herein used platinum‐group HEA nanocubes, initially enclosed by well‐defined {100} facets, as electrocatalysts for the multistep ethanol oxidation reaction (EOR). Notably, the prepared catalysts demonstrate an 8.3‐fold enhancement in specific activity during electrochemical cycling, driven by the structural evolution of catalyst facets. This transformation leads to a severely beveled cubic morphology characterized by an approximately equal distribution of {100}, {110}, and {111} facets, while preserving the compositional homogeneity and high‐entropy nature, as confirmed by high‐resolution transmission electron microscopy and synchrotron‐based x‐ray absorption spectroscopy. In situ surface‐enhanced infrared absorption spectroscopy, electrochemical stripping experiments, and computational calculations reveal that the enhanced performance originates from improved C─C bond cleavage and superior resistance to poisoning by formate intermediates (HCOO ad ). These features promote complete oxidation of ethanol to CO 2 , a critical step for maximizing efficiency in direct alcohol fuel cells for renewable energy applications.