Boron-Doped Carbon Coatings Stabilize Cu+/Cu0 Interfaces to Promote Multicarbon Formation in CO2 Electroreduction.

The construction of a stable Cu+/Cu0 reaction interface is a promising yet challenging strategy for the electrosynthesis of multicarbon (C2+) products from CO2 reduction. Herein, we report a dual-phase Cu2O/Cu catalyst encapsulated by boron (B)-doped carbon coatings (BC), denoted as Cu2O(Cu)@BC. In a flow cell system with 1 M KOH electrolyte, this catalyst delivers a maximum C2+ Faradaic efficiency of 83.4% at -0.7 V versus the reversible hydrogen electrode (RHE) and a partial C2+ current density of 460 mA cm-2 at -0.9 V versus RHE, while maintaining stable operation for over 42 h. This performance surpasses that of its counterpart without the BC coatings and other Cu-based catalyst systems. Comprehensive experimental investigations reveal that the BC coatings facilitate the formation of Cu+ species with higher oxidation states and stabilize the Cu+/Cu0 interface under reductive conditions. The resulting abundant and stable interfacial sites significantly increase *CO intermediate surface coverage, facilitating carbon-carbon coupling and promoting the formation of the key *OCH2CH3 intermediate for C2+ production. This work offers an effective strategy to maintain a high density of Cu+/Cu0 interfacial active sites and provides deeper insights into the stabilization and degradation mechanisms of Cu-based catalysts for efficient electrochemical CO2-to-C2+ conversion.