Photo-thermal CO2 desorption from amine-modified silica / carbon aerogel for direct air capture

Abstract

Direct air capture (DAC) is a promising approach for combating global warming, but its energy-intensive CO2 desorption process presents a significant challenge. Especially, the DAC process requires much amount of thermal energy by heating the adsorbent for CO2 desorption. In order to eliminate the heating for CO2 desorption, we have developed an amine-modified silica / carbon (AmSiC) aerogel that can desorb CO2 by light irradiation, utilizing carbon black as a photo-thermal material. The AmSiC aerogel with high porosity was obtained via a supercritical CO2 drying method at 20 MPa and 40 ˚C for 3 h, enabling CO2 adsorption due to its amine content. After the aerogel adsorbed CO2 from the air, LED light with the intensity of 2.0 kW m−2 was irradiated to the aerogel with CO2, raising the temperature to approximately 70 ˚C and leading to CO2 desorption. Compared to xerogel dried through heating evaporation, the AmSiC aerogel exhibited approximately 60 times higher CO2 desorption due to its porous structure serving as thermal insulation during photo-thermal heating. By adjusting the carbon black concentration, the photo-thermal desorption efficiency reached nearly 80 %. Solar illumination can be employed in the DAC process with the AmSiC aerogel, which would significantly reduce the energy requirements for DAC system operation.