A‐Site Cation‐Regulated <i>Operando</i> Restructuring of Cu‐Based Perovskite Oxides for Selective Carbon Monoxide Electroreduction

Understanding the correlation between surface catalytic motifs and electrochemical reaction pathways is crucial for the rational design of high-performance electrocatalysts, yet remains hindered by the dynamic reconfiguration of active sites under operating conditions. In this study, we establish a tunable platform based on a series of Cu-based perovskite oxides with systematically varied A-site cations to investigate how A-site chemistry regulates the structural dynamics of Cu and its interplay with the carbon monoxide reduction (COR) pathway. Operando spectroscopic analyses reveal that those perovskites with alkaline-earth A-site cations promote Cu clustering into metallic states, favoring multicarbon product formation. In contrast, rare-earth A-site perovskites stabilize surface Cu⁺ species through strong Cu-O interactions, thereby enhancing the selectivity of methane. Complementary theoretical calculations further demonstrate that the Cu─O bond strength-modulated by A-site composition-dictates the electrochemical stability of Cu active sites. These findings underscore the pivotal role of local coordination environments in steering catalyst reconstruction and product distribution, and provide guiding principles for A-site engineering in perovskite-based COR catalysts.