Cerium Dioxide-Induced Abundant Cu⁺/Cu⁰ Sites for Electrocatalytic Reduction of Carbon Dioxide to C₂₊ Products

In recent years, the electrochemical reduction of carbon dioxide (CO₂RR) has made many advances in C₂₊ production. Cu⁺/Cu⁰ site is beneficial for C-C coupling process, but the oxidation state of copper cannot be well maintained during the reaction process, resulting in a decrease in catalyst activity. Based on this consideration, in this work, transition metal oxide CeO₂ with a hollow cube structure and oxygen vacancies was introduced to stabilize and increase Cu⁺/Cu⁰ active sites (Ce₁Cu₂). The catalyst exhibits excellent CO₂RR performance, with FE_C2+ achieving 73.52 % and j_C2+ >280 mA/cm² at 1.26 V (vs. RHE). Ethanol is the main C₂₊ product and FE_ethanol reaches 39 % at 1.26 V. The experimental results indicate that the presence of CeO₂ provides a large number of oxygen vacancies and forming Cu⁺-O^2--Ce⁴⁺ structure by the strong interaction of CeO₂ and Cu NPs. The structure of Cu⁺-O^2--Ce⁴⁺ and abundant oxygen vacancies lay a good foundation for the CO₂ adsorption. Moreover, it increases the content of Cu⁺/Cu⁰ sites, effectively inhibiting hydrogen evolution reaction, promoting the C-C coupling interaction, thereby facilitating the generation of C₂₊ products. The DFT theoretical calculation further demonstrates that Ce₁Cu₂ is more inclined towards the ethanol pathway, confirming its high selectivity for ethanol.