Zn-Based Catalysts for Selective and Stable Electrochemical CO2 Reduction at High Current Densities

Practical electrochemical carbon dioxide (CO2) reduction requires the development of selective and stable catalysts based on low-cost and Earth-abundant materials. In this work, we develop catalysts for CO2 conversion to CO based on ZnO with various morphologies, including nanoparticles, nanorods, nanosheets, and random shapes. We found that ZnO nanorods exhibit the highest CO2 to CO efficiency, with a high CO Faradaic efficiency (FE) of over 80% in a current density range of 50–160 mA cm2 in both flow-cell and membrane electrode assembly (MEA) reactors. We found that the CO selectivity of ZnO-based catalysts slowly decreased over time at high current densities because of the depletion of the ZnO phase. We have developed an in-situ regeneration strategy for catalysts that involves periodic oxidations of the catalysts during electrochemical CO2 reduction. Using this approach, we have demonstrated the conversion of CO2 to CO with a stable CO FE of above 80% for 100 h at a current density of 160 mA cm–2.