Confined CuⅠ sites in partially electro-reduced 2D conductive Cu-MOF film for boosting CO2 electrocatalysis to C2 products

Cu-based catalysts, especially co-sites of Cu 0 and Cu Ⅰ , are the best competitors for electrochemical CO 2 fixation to produce multi-carbon (C2 + ) products. However, it is challenging to construct highly stable Cu Ⅰ sites due to the changeability of its valence state and electronic structure in the electroreduction process, and the mechanism is also elusive. Herein, a 2D conductive Cu Ⅱ -MOF film (Cu Ⅱ HHTP@Cu 0 ) is prepared on Cu (1   0   0) foil by in-situ electrochemical assembly. After pre-reduction, the in-situ produced Cu 2 O clusters are confined in the cavities of the film created by the local breaking of the MOF framework to construct a unique Cu Ⅰ -Cu Ⅱ HHTP@Cu 0 catalyst, so that a novel strategy is proposed to stablize highly dispersed Cu Ⅰ sites during electrochemical reduction, thus protecting the Cu 2 O clusters from further reduction and ensuring the coexistence of Cu Ⅰ (1   1   1)-Cu 0 (1   0   0) sites. As such, the current density of CO 2 electrochemical reduction catalyzed by this catalyst exceeds 300 mA cm −2 , the duration overs 50 h, and the C2 selectivity achieves 72.6 %. In-situ spectroscopy and theoretical calculations reveal that the optimized microenvironment of the Cu Ⅰ (1   1   1) sites reduces the energy barrier of *OCCOH coupling, and Cu 0 (1   0   0) sites increase the coverage of *CO, thus boosting the production of C2 products.