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 (HCOOad). These features promote complete oxidation of ethanol to CO2, a critical step for maximizing efficiency in direct alcohol fuel cells for renewable energy applications.