Boosting CO₂ Electroreduction to Multi-carbon Products via Oxygen-rich Vacancies and Ce⁴⁺−O²⁻−Cu⁺ Structure in Cu/CeO₂ for Stabilizing Cu⁺

Cu is a promising electrocatalyst for the CO₂ reduction reaction (CO₂RR) to produce high-value C₂₊ products. Due to the fierce competition of the hydrogen evolution reaction, the slow diffusion of CO₂, and the high energy barrier of the C−C coupling reaction, it is still challenging to achieve high activity and high selectivity to produce multi-carbon products on copper-based electrocatalysts. In this work, we synthesized Cu/CeO₂ catalysts with varying amounts of Cu doping, aiming at effectively converting CO₂ into C₂₊ products through electroreduction. At a copper doping level of 9.77 wt%, the catalyst exhibited a current density of 16.8 mA cm⁻² using a standard H-type cell, achieving a C₂₊ faradaic efficiency (FE) of 78.3 %. Through additional experiments and material characterization, we confirmed that controlling the Cu loading on the surface of CeO₂ is an effective way to regulate the ratio of Cu⁺ to Cu⁰ active sites and the number of oxygen vacancies. Furthermore, the strong electron interaction between Ce⁴⁺−O²⁻−Cu⁺ structure can stabilize Cu⁺ species and enhance the overall stability of the catalyst. This strategy enhances the selectivity towards C₂₊ products and effectively suppresses the competing hydrogen evolution reaction.