(127f) Electrochemical CO2 Conversion to Valuable Chemicals

Converting greenhouse gas carbon dioxide (CO₂) to value-added chemicals is an appealing approach to tackle CO₂ emission challenges. The chemical transformation of CO₂ requires suitable catalysts that can lower the activation energy barrier to minimize the energy penalty associated with the CO₂ reduction reaction. Cu is the only monometallic catalyst that can produce an appreciable amount of C2+ products from CO2, while the C2+ selectivity of Cu must be further improved in order to be considered for commercialization. Here, we will present our work in developing an integrated two-stage electrolyzer stack system for the conversion of CO₂ to alcohols. The first stage utilizes a silver catalyst in a flow cell capable of reducing CO₂ to CO with faradaic efficiencies of >95% and partial current densities of >200 mA/cm². For the second stage, a CO reduction flow cell using alkaline electrolyte can reduce CO to C2+ products with high selectivity and high current density. We recently constructed a high-performance CO flow electrolyzer with a well-controlled electrode-electrolyte interface that can reach total current densities up to 1 A/cm² together with improved C₂₊ selectivities. Computational transport modelling and isotopic C¹⁸O reduction experiments suggest that the enhanced activity is due to a higher surface pH under CO reduction conditions, which facilitated the production of acetate. At optimal operating conditions, we achieved a C₂₊ Faradaic efficiency of ~91% with a C₂₊ partial current density over 630 mA/cm². Further investigations show that maintaining an efficient triple-phase boundary at the electrode-electrolyte interface is the most critical challenge to achieving a stable CO/CO₂ electrolysis process at high rates.