Abstract
Electrolyzers can reduce CO2 into products at high reaction rates, but are often limited by low energy efficiency and low CO2 utilization efficiency. Here, we report an electrolyzer that reduces 3.0 M KHCO3 into CO at a partial current density of 220 mA cm–2, a CO2 utilization efficiency of 40%, and a cell voltage of 2.3 V. This performance is enabled by using a reactive carbon solution feedstock, a cation exchange membrane, and the hydrogen oxidation reaction at the anode. This study highlights how feedstock, membrane, and anode chemistry control the rate and efficiency of CO2 conversion.