Zn-Based\nCatalysts for Selective and Stable Electrochemical\nCO₂ Reduction at High Current Densities

Abstract

Practical\nelectrochemical carbon dioxide (CO₂) reduction\nrequires the development of selective and stable catalysts based on\nlow-cost and Earth-abundant materials. In this work, we develop catalysts\nfor CO₂ conversion to CO based on ZnO with various morphologies,\nincluding nanoparticles, nanorods, nanosheets, and random shapes.\nWe found that ZnO nanorods exhibit the highest CO₂ to CO\nefficiency, with a high CO Faradaic efficiency (FE) of over 80% in\na current density range of 50–160 mA cm² in both\nflow-cell and membrane electrode assembly (MEA) reactors. We found\nthat the CO selectivity of ZnO-based catalysts slowly decreased over\ntime at high current densities because of the depletion of the ZnO\nphase. We have developed an in-situ regeneration strategy for catalysts\nthat involves periodic oxidations of the catalysts during electrochemical\nCO₂ reduction. Using this approach, we have demonstrated\nthe conversion of CO₂ to CO with a stable CO FE of above\n80% for 100 h at a current density of 160 mA cm^–2.