Boron‐Doped Carbon Coatings Stabilize Cu + /Cu 0 Interfaces to Promote Multicarbon Formation in CO 2 Electroreduction

The construction of a stable Cu + /Cu 0 reaction interface is a promising yet challenging strategy for the electrosynthesis of multicarbon (C 2+ ) products from CO 2 reduction. Herein, we report a dual‐phase Cu 2 O/Cu catalyst encapsulated by boron (B)‐doped carbon coatings (BC), denoted as Cu 2 O(Cu)@BC. In a flow cell system with 1 M KOH electrolyte, this catalyst delivers a maximum C 2+ Faradaic efficiency of 83.4% at −0.7 V versus the reversible hydrogen electrode (RHE) and a partial C 2+ 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 + /Cu 0 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 *OCH 2 CH 3 intermediate for C 2+ production. This work offers an effective strategy to maintain a high density of Cu + /Cu 0 interfacial active sites and provides deeper insights into the stabilization and degradation mechanisms of Cu‐based catalysts for efficient electrochemical CO 2 ‐to‐C 2+ conversion.