Electrochemical direct air capture of CO2 using neutral red as reversible redox-active material

Electrochemical direct air capture (DAC) of CO2 requires air-stable redox-active materials. Here, the authors present an electrochemical DAC using air-stable redox couple of neutral red with a minimum energy requirement of 65 kJ(e)/mol(CO2). Direct air capture of carbon dioxide is a viable option for the mitigation of CO2 emissions and their impact on global climate change. Conventional processes for carbon capture from ambient air require 230 to 800 kJ thermal per mole of CO2, which accounts for most of the total cost of capture. Here, we demonstrate electrochemical direct air capture using neutral red as a redox-active material in an aqueous solution enabled by the inclusion of nicotinamide as a hydrotropic solubilizing agent. The electrochemical system demonstrates a high electron utilization of 0.71 in a continuous flow cell with an estimated minimum work of 35 kJ(e) per mole of CO2 from 15% CO2. Further exploration using ambient air (410 ppm CO2 in the presence of 20% oxygen) as a feed gas shows electron utilization of 0.38 in a continuous flow cell to provide an estimated minimum work of 65 kJ(e) per mole of CO2.