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

The electrochemical reduction of CO2 presents a promising pathway for storing intermittent renewable energy in the form of chemical bonds, thereby mitigating CO2 emissions and enabling the production of sustainable fuels. In this work, we demonstrate nanoscale engineering of oxygen vacancy and morphology simultaneously on Cu2O catalysts for electrochemical reduction of CO2 to liquid products (formate and ethanol). By comparing the performance of cube- and tetrakaidecahedron-like Cu2O catalysts, we have demonstrated that the flower-like Cu2O catalyst, enclosed with rich oxygen vacancy defects, exhibited superior performance in the reduction of CO2 to liquid products. Moreover, the synergetic role of Cu+ also contributed to the enhanced activity by promoting CO2 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 μmol 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 CO2 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 CO2 into liquid products.