Reconstruction-Dependent Coordination Descriptor for Selectivity toward C2+ Products of CO2 Electroreduction over Cu Catalysts

The electroreduction of CO2 (CO2ER) to multicarbon chemicals (C2+) catalyzed by copper (Cu) is a pivotal initiative for achieving carbon neutrality and green chemical production. However, a lack of quantitative structure-selectivity relationship hampers further advancement of Cu catalysts. Moreover, the inherent structural fluidity of Cu catalysts, which facilitates its surface reconstruction during the CO2ER reaction, complicates the mutual verification and self-consistency between theoretical and experimental results. In this study, we employ grand-canonical first-principles calculations under solvent and cation effects to elucidate the negative correlation between C2+ selectivity in CO2ER and the coordination saturation of monometallic Cu catalysts. Through systematic analysis of CO-induced reconstruction of various Cu surfaces, we introduce the concept of degree of reconstruction (DOR) to quantitatively characterize the dynamic behavior of Cu surfaces. Additionally, we propose reconstruction-dependent generalized coordination numbers (RD-GCNs) as a descriptor to accurately capture the C2+ selectivity trends observed in electrocatalytic environments. The identified negative correlation between RD-GCNs and C2+ selectivity demonstrates that a lower RD-GCN notably enhances C2+ selectivity, accurately reproducing the relative order of experimental Faradaic efficiency (FE) for C2+ products among Cu single-crystal slabs and rationalizing the C2+ selectivity trend among monometallic Cu nanostructures with diverse morphology and roughness from available experimental references. This work provides significant insights into the impact of dynamic structural fluxionality of Cu catalysts on C2+ product selectivity, which lays the theoretical foundation and broadens the ideas for rational design of Cu-based catalysts for electroreduction conversions of CO2 to C2+ products.