Energy-efficient electrochemical CO2 capture from the atmosphere

In this contribution, we report on the experimental demonstration of a continuously operating modified fuel cell capable of capturing CO2 at atmospheric concentrations with record efficiency. The atmosphere provides O2 and CO2 at the cathode, with CO2 transported from the cathode to the anode as HCO3- and CO3-- ions. These ions then combine with H+ ions at the anode to form concentrated CO2 gas. We measure the energy expended per amount of CO2 captured, and find that our system is the most energy-efficient atmospheric CO2 capture device demonstrated to date, greatly improving on our previously reported results. Other demonstrations of electrochemical CO2 capture [2] have focused on higher CO2 concentrations (800 ppm - 4300 ppm) as they were designed for the removal of CO2 from enclosed spaces like submarines and space shuttles, not the atmosphere. For comparison, at 800 ppm our system uses two times less energy (< 2 MW-hr/ton) than previous demonstrations.