Identification of Cu(100)/Cu(111) Interfaces as Superior Active Sites for CO Dimerization During CO₂ Electroreduction

The electrosynthesis of valuable multicarbon chemicals using carbon dioxide (CO₂) as a feedstock has substantially progressed recently but still faces considerable challenges. A major difficulty lines in the sluggish kinetics of forming carbon-carbon (C-C) bonds, especially in neutral media. We report here that oxide-derived copper crystals enclosed by six {100} and eight {111} facets can reduce CO₂ to multicarbon products with a high Faradaic efficiency of 74.9 ± 1.7% at a commercially relevant current density of 300 mA cm^-2 in 1 M KHCO₃ (pH ∼ 8.4). By combining the experimental and computational studies, we uncovered that Cu(100)/Cu(111) interfaces offer a favorable local electronic structure that enhances *CO adsorption and lowers C-C coupling activation energy barriers, performing superior to Cu(100) and Cu(111) surfaces, respectively. On this catalyst, no obvious degradation was observed at 300 mA cm^-2 over 50 h of continuous operation.