Dynamic Structural Persistence of Trinuclear Cu Motifs toward CO2 Electroreduction

Abstract

Electrochemical CO2 reduction toward multi-carbon products is often attributed to adjacent Cu sites that enable *CO coupling, yet whether designed Cu–Cu motifs persist under reaction conditions remains unclear. Here, we investigate a series of trinuclear Cu catalysts with similar initial coordination structures but different steric rigidity in the secondary coordination shell. Operando Raman and X-ray absorption spectroscopies reveal that catalysts with insufficient steric constraint undergo asymmetric Cu–Cu distortion under cathodic bias, leading to heterogeneous *CO adsorption behavior and enhanced C1 pathways. In contrast, sterically stabilized catalysts preserve symmetric Cu–Cu configurations and sustain favorable *CO–*CO coupling toward C2+ formation. These findings demonstrate that geometric persistence of neighboring Cu sites under operating conditions, rather than the initial structure alone, governs catalytic selectivity in CO2 electroreduction and highlights the importance of operando characterization for identifying active-state structures.