Understanding the influences and mechanism of water vapor on CO2 capture by high-temperature Li4SiO4 sorbents

Li 4 SiO 4 sorbent attracts wide attention due to its high and stable CO 2 adsorption. However, the process of CO 2 capture is significantly affected by various impurities under the circumstance of industrial applications, and water vapor is one such impurity that needs to be well studied. Herein, we aim to evaluate the effect of water vapor on physicochemical characteristics of Li 4 SiO 4 -based sorbents during cyclic CO 2 adsorption and desorption and to understand the action mechanism of H 2 O molecules on CO 2 adsorption by Li 4 SiO 4 . Reaction tests show that water vapor can significantly enhance CO 2 adsorption performance of sorbents, but the promotion effect varies with the different presence of water vapor during reactions. Material characterization and DFT calculation reveal that although the presence of water vapor leads to deterioration of internal pore structure of the sorbent, H 2 O molecule will form OH – on the surface of Li 4 SiO 4 and further react with CO 2 to generate HCO 3 – , thus the adsorption energy with water vapor presenting is increased with an observation of promoted CO 2 adsorption.