Formation of Enriched Vacancies for Enhanced CO₂ Electrocatalytic Reduction over AuCu Alloys

Electroreduction (ER) of carbon dioxide (CO₂) is a promising way to curb excessive CO₂ emission and produce value-added products. Gold–copper (AuCu) alloys are known to exhibit eminent CO production performance toward CO₂ER. However, it still remains a grand challenge to balance *COOH and *CO bonding and to further decrease CO onset potential. This Letter describes the construction of Cu vacancies at an abrupt surface over a dealloyed AuCu catalyst to effectively decrease the overpotential and increase CO faradaic efficiency. Dealloyed Au₃Cu exhibited a 90.2% CO faradaic efficiency at −0.38 V vs RHE and a 418.60 A/g CO mass current density at −0.8 V. vs RHE, achieving the record for CO production among AuCu catalysts. Combining the experimental and theoretical results, we concluded that the improved performance primarily results from the enhanced *COOH absorption.