In Situ Engineering of the Cu⁺/Cu⁰ Interface to Boost C₂₊ Selectivity in CO₂ Electroreduction

The Cu⁺/Cu⁰ interface in the Cu-based electrocatalyst is essential to promote the electrochemical reduction of carbon dioxide (ERCO₂) to produce multi-carbon hydrocarbons and alcohols with high selectivity. However, due to the high activity of the Cu⁺/Cu⁰ interface, it is easy to be oxidized in the air. How to control and prepare a Cu-based electrocatalyst with an abundant and stable Cu⁺/Cu⁰ interface in situ is a huge challenge. Here, combined with density functional theory (DFT) calculations and experimental studies, we found that the trace halide ions adsorbed on Cu₂O can slow the reduction kinetics of Cu⁺ → Cu⁰, which allowed us to in-situ well control the synthesis of the CuO-derived electrocatalyst with rich Cu⁺/Cu⁰ interfaces. Our Cu catalyst with a rich Cu⁺/Cu⁰ interface exhibits excellent ERCO₂ performance. Under the operation potential of -0.98 V versus RHE, the Faraday efficiency of C₂H₄ and C₂₊ products are 55.8 and 75.7%, respectively, which is about 16% higher than that of CuO-derived electrocatalysts that do not use halide ions. The high ${FE}_{C_{2+}}$ comes from the improvement of the coupling efficiency of reaction intermediates such as CO-CO, which is proved by DFT calculations, and the suppression of hydrogen evolution reaction. Therefore, we provide an in-situ engineering strategy, which is simple and effective for the design and preparation of high-performance ERCO₂ catalysts.