Boosting the electroreduction of CO2 to liquid products via nanostructure engineering of Cu2O catalysts

The electrochemical reduction of CO 2 presents a promising pathway for storing intermittent renewable energy in the form of chemical bonds, thereby mitigating CO 2 emissions and enabling the production of sustainable fuels. In this work, we demonstrate nanoscale engineering of oxygen vacancy and morphology simultaneously on Cu 2 O catalysts for electrochemical reduction of CO 2 to liquid products (formate and ethanol). By comparing the performance of cube- and tetrakaidecahedron-like Cu 2 O catalysts, we have demonstrated that the flower-like Cu 2 O catalyst, enclosed with rich oxygen vacancy defects, exhibited superior performance in the reduction of CO 2 to liquid products. Moreover, the synergetic role of Cu + also contributed to the enhanced activity by promoting CO 2 adsorption and facilitating C -C coupling. As a result, the peak Faradaic efficiency (FE) for liquid products of 95.5 % was obtained, associated with a high ethanol FE of 52.6 % and formation rate of 23.8 mu mol h -1 cm -2 within a H-cell. Furthermore, within a flow cell configuration, we have observed a significant improvement in the generation of formate, maintaining FE values above 70 % even under high current densities of up to 400 mA cm -2 . In -situ Raman spectroscopic measurements allow us to identify and track key intermediates involved in the CO 2 reduction to formate and ethanol. This detailed understanding of the reaction pathways adds to our fundamental knowledge and provides valuable insights for the development of morphology-controlled electrocatalysts targeting efficient conversion of CO 2 into liquid products.