Stabilization of oxidized Cu species via CeOx nano-islands for enhanced CO2 reduction to C2+ products

Abstract The presence of oxidized copper species (CuOx) on metallic Cu surfaces is widely acknowledged as a critical factor for promoting C–C coupling during CO2 reduction reactions (CO2RR). However, the inherent instability of CuOx under negative potentials, where it is prone to reduction to metallic Cu, remains a formidable challenge. In this study, we developed a CeOx-modified CuO catalyst for the CO2RR, featuring CeOx uniformly distributed as isolated nano-islands on CuO nanoparticles. Upon reduction of the CuO matrix to metallic Cu, the CeOx layer effectively stabilizes the interfacial CuOx, preventing its further reduction. Operando characterization verified the sustained presence of Cu2+ and Cu+ species at highly reductive potentials, underscoring the role of CeOx in preserving CuOx stability. Theoretical calculations revealed that Ce3+ enhances the formation energy of oxygen vacancies, stabilizing the CuOx interface and *OC–CO intermediates, which are crucial for C–C coupling. With this surface modification strategy, the catalyst achieved a remarkable C2+ faradaic efficiency of 78% at −700 mA cm−2, while demonstrating persistent performance with a faradaic efficiency exceeding 70% for C2+ products at −100 mA cm−2 for over 110 hours. These findings present an effective strategy for stabilizing metal oxides and advancing durable CO2RR catalysts.