Electrolytic pathway for upgrading waste CO2 into syngas with a carbon capture and utilization energy efficiency greater than 50%

Captured CO₂ can either be stored or converted into a carbon-containing product. Both processes require energy to liberate CO₂ from the CO₂ capture solution. One way to bypass the energy-intensive recovery of CO₂ is to integrate CO₂ capture and conversion. For example, OH^--based capture solutions react with CO₂ to form (bi)carbonate-rich liquids, which can then be electrochemically converted into upgraded carbon-containing products while regenerating OH^- for further CO₂ capture. However, bicarbonate electrolyzers designed to mediate this process are often characterized by high voltages (e.g., >3 V at 100 mA cm^-2). We report here a bicarbonate electrolyzer that operates at 100 mA cm^-2 with an applied voltage of 2.7 V at 50 °C. This lower voltage was made possible by designing a bicarbonate electrolyzer with a cationic exchange membrane that uses a neutral anolyte (3 M KHCO_3(aq)) to minimize the thermodynamic potential for the oxygen evolution reaction. This bicarbonate electrolyzer enables a carbon capture and utilization energy efficiency for an electrochemical process that is comparable to thermochemical CO₂ conversion for syngas production.