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

Li4SiO4 sorbent attracts wide attention due to its high and stable CO2 adsorption. However, the process of CO2 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 Li4SiO4-based sorbents during cyclic CO2 adsorption and desorption and to understand the action mechanism of H2O molecules on CO2 adsorption by Li4SiO4. Reaction tests show that water vapor can significantly enhance CO2 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, H2O molecule will form OH- on the surface of Li4SiO4 and further react with CO2 to generate HCO3 -, thus the adsorption energy with water vapor presenting is increased with an observation of promoted CO2 adsorption.