Electrochemical Regeneration of Spent Alkaline Absorbent from Direct Air Capture.

CO capture from the atmosphere (or direct air capture) is widely recognized as a promising solution to reach negative emissions, and technologies using alkaline solutions as absorbent have already been demonstrated on a full scale. In the conventional temperature swing process, the subsequent regeneration of the alkaline solution is highly energy-demanding. In this study, we experimentally demonstrate simultaneous solvent regeneration and CO desorption in a continuous system using a H-recycling electrochemical cell. A pH gradient is created in the electrochemical cell so that CO is desorbed at a low pH, while an alkaline capture solution (NaOH) is regenerated at high pH. By testing the cell under different working conditions, we experimentally achieved CO desorption with an energy consumption of 374 kJ·mol CO and a CO purity higher than 95%. Moreover, our theoretical calculations show that a minimum energy consumption of 164 kJ·mol CO could be achieved. Overall, the H-recycling electrochemical cell allowed us to accomplish the simultaneous desorption of high-purity CO stream and regeneration of up to 59% of the CO capture capacity of the absorbent. These results are promising toward the upscaling of an energy-effective process for direct air capture.