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

Abstract 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.