Coupling of Cu(100) and (110) Facets Promotes Carbon Dioxide Conversion to Hydrocarbons and Alcohols

Abstract Copper can efficiently electro‐catalyze carbon dioxide reduction to C 2+ products (C 2 H 4 , C 2 H 5 OH, n‐propanol). However, the correlation between the activity and active sites remains ambiguous, impeding further improvements in their performance. The facet effect of copper crystals to promote CO adsorption and C−C coupling and consequently yield a superior selectivity for C 2+ products is described. We achieve a high Faradaic efficiency (FE) of 87 % and a large partial current density of 217 mA cm −2 toward C 2+ products on Cu(OH) 2 ‐D at only −0.54 V versus the reversible hydrogen electrode in a flow‐cell electrolyzer. With further coupled to a Si solar cell, record‐high solar conversion efficiencies of 4.47 % and 6.4 % are achieved for C 2 H 4 and C 2+ products, respectively. This study provides an in‐depth understanding of the selective formation of C 2+ products on Cu and paves the way for the practical application of electrocatalytic or solar‐driven CO 2 reduction.