Local Coordination‐Dependent CO ₂ Reduction Activity of Bimetallic Cu─Al Catalysts for Selective Ethylene/Ethanol Electrosynthesis

The formation of bimetallic catalysts has been widely adopted to improve CO₂ reduction selectivity. However, discrepancies in product distribution in the literature, even among catalysts with identical bimetal compositions, suggest the involvement of distinct reaction pathways. Here, we report that ethylene and ethanol selectivity are strongly influenced by the atomic coordination of metals. We prepared two model catalysts, namely interface-CuAl (dominated by Cu/CuAlO₂ interfaces) and doping-CuAl (with Al doped into the Cu lattice). Both catalysts demonstrate excellent C₂₊ Faradaic efficiency (FE) of 65%-85%. However, interface-CuAl primarily produces ethylene with an FE of 67.6%, seven-fold higher than FE_ethanol. Conversely, doping-CuAl favors ethanol production, reaching a maximum FE_ethanol of 43.7%, four times higher than FE_ethylene. Extended X-ray absorption fine structure and in situ Fourier transform infrared spectrometry reveal distinct adsorption abilities of Cu and different intermediate coverages. Complementary theoretical calculation further elucidates the critical role of *CHCOH bifurcation. Specifically, favorable C-O cleavage at interface-CuAl promotes ethylene production, whereas Cu-C scission at doping-CuAl favors ethanol production. Beyond CO₂ electroreduction, CuAl catalysts also demonstrate phase-dependent nitrate reduction activity, underscoring the importance of atomic coordination in catalysis. This study provides fundamental insights into the structure-selectivity relationship of bimetallic catalysts for selective chemical production.