Steering Acidic CO 2 Electroreduction to Multicarbon Alcohols with High Efficiency and Selectivity over Calcium-Induced Bicrystalline Cu Architecture

Electroreduction of CO 2 to multicarbon (C 2+ ) alcohols in an acidic electrolyte presents a promising route for efficient carbon utilization. However, achieving high selectivity with high current density remains a major challenge due to multiple competing reactions in an acidic electrolyte. Herein, we develop a Ca species-templated strategy to construct bicrystalline Cu architectures (dCu(OH) 2 /Ca x ) for the selective conversion of CO 2 to C 2+ alcohols in acid. At a high current density of 700 mA cm –2, the C 2+ product faradaic efficiency (FE) could reach 81.2%, of which the FE of C 2+ alcohols was 51.6% with a partial current density of 361.4 mA cm –2, which is higher than those reported in acidic electrolytes. The C 2+ alcohol/C 2 H 4 ratio was as high as 1.9, compared with the 0.48 observed for the dCu(OH) 2 electrode. Mechanistic studies reveal that Ca species act as templates, directing the formation of 3D dendritic bicrystalline Cu structures rich in Cu (111)/(200) interfaces. These interfaces significantly enhance the adsorption of hydroxyl groups (*OH ad ) in an acidic electrolyte, which plays a dual role in promoting the conversion of CO 2 to C 2+ alcohols in acid. The *OH ad -functionalized Cu (111)/(200) interfaces not only suppress the hydrogen evolution reaction by altering the hydrogen-bonding network of interfacial water but also stabilize the key *CHCOH intermediate, facilitating its hydrogenation to *CHCH x OH for the generation of C 2+ alcohols. This synergistic interplay between the catalyst structure and interfacial chemistry enables efficient and selective production of C 2+ alcohols in acidic environments.