Insights into the mechanism of the capture of CO by KCO sorbent: a DFT study.

The adsorption and reactions of CO and HO on both monoclinic and hexagonal crystal KCO were investigated using the density functional theory (DFT) approach. The calculated adsorption energies showed that adsorption of HO molecules was clearly substantially stronger on the KCO surface than the adsorption of CO, except on the (001)-1 surface of hexagonal KCO, where CO is competitively adsorbed with HO. Carbonation reactions easily occur on pure KCO and involve two parallel paths: one is where adsorbed HO reacts with molecular CO in gas to form the bicarbonate, while the other is where HO dissociates into OH and H before bicarbonate formation, and then OH reacts with gaseous CO to form a bicarbonate. Our results indicate that adding a support or promoter or using a special technique to expose more (001)-1 surfaces in hexagonal KCO may improve the conversion of CO to the bicarbonate, which provides a theoretical direction for the experimental preparation of the KCO sorbent to capture CO.