Adsorption behavior of atmospheric CO2 with/without water vapor on CeO2 surface

Abstract

The significance of investigations into CO2 adsorption from the air has been steadily on the rise in recent years. CeO2 is known as an effective catalyst for CO2 transformation and adsorbent of CO2, however, the study on the adsorption of low concentrations of CO2 on CeO2 and the effect of water vapor on the adsorption of CO2 on CeO2 is very limited. Herein, the adsorption behavior of low concentration of CO2, particularly atmospheric CO2 (0.04 vol%), on CeO2 and the effect of water vapor on the CO2 adsorption were investigated by in situ FT-IR, mass spectroscopies, and DFT calculations. Low concentrations of CO2 can be effectively adsorbed on CeO2, and typical four CO2 adspecies such as bidentate carbonate, hydrogen carbonate, monodentate carbonate, and polydentate carbonate were formed on CeO2. The CO2 adsorption amount on CeO2 was increased by 20% by the presence of water vapor compared with that in the absence of water vapor. Based on FT-IR analyses and DFT calculations, the adsorption strength of CO2 is comparable to that of water on CeO2, and the water adspecies will assist the adsorption of CO2 via hydrogen bonding, leading to the increase of CO2 adsorption amount.