Achieving a viable solar-driven EC CO2 reduction energy conversion efficiency requires minimizing potential losses in all aspects of the device including the cathode, anode, electrolyte, and membrane. Achieving selective products requires management of multi-electron transfer reactions . Strategies to optimize each component (anode, cathode, electrolyte, cell design) of our CO2 electrolyzer cell to obtain high selectivity and energy conversion efficiency at low overpotential will be described. An overall cell design which has efficient gas to liquid mass transfer of CO2 is employed . Use of a CsHCO3 buffered electrolyte increases selectivity to C2+ products such as ethylene and ethanol . A nanostructured anode is used which shows superior stability and high performance for oxygen evolution in the pH range of interest for CO2 reduction. Finally, a cathode design has been developed which enables selectivity to hydrocarbons and oxygenates over a wide range of pH and cell voltage conditions.
Solar-driven CO2 reduction is accomplished by coupling the optimized electrolysis device to solar cells. 1 sun efficiencies of over 4% for the production of hydrocarbons and oxygenates are achieved. Notably, the overall system also functions at >1% conversion efficiency at illumination intensities down to 0.3 suns.
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