Stabilizing Cu 0 /Cu + Interfaces via High‐Entropy Electrochemical Potential Regulation Strategy for Enhanced CO 2 ‐to‐Ethylene Conversion in Acidic Medium

Abstract The electrochemical CO 2 reduction reaction (CO 2 RR) in acidic media represents an efficient carbon‐negative strategy, mitigating greenhouse effects while selectively producing value‐added multi‐carbon compounds. The Cu 0 /Cu + interfaces could promote C─C coupling processes, but preserving the interface integrity under highly reductive potentials and acidic conditions presents substantial challenges. Here, a high‐entropy electrochemical potential regulation strategy is reported that leverages high‐entropy doping synergy to atomically tailor the surface electronic structure of Cu‐based catalysts. This strategy creates an electron shield effect around the host element (Cu), protecting it from excessive reduction and facilitating the formation and stabilization of Cu 0 /Cu + interfaces during acidic CO 2 RR. Comprehensive operando characterizations combined with density functional theory calculations reveal that the electron shield effect strategically modulates the electron‐accepting capability of Cu. The optimized surface electronic structure facilitates C─C coupling, significantly enhancing the CO 2 ‐to‐C 2+ conversion efficiency. The designed catalyst achieves a remarkable Faradaic efficiency of 66.7% for ethylene production at −1.69 V vs the reversible hydrogen electrode in acidic electrolyte (pH 2), while maintaining excellent stability with an average ethylene Faradaic efficiency of 63.1% over 52‐h continuous operation. This work establishes a new strategy for designing and stabilizing active interfaces of copper‐based electrocatalysts for efficient and durable acidic CO 2 electroreduction.