K2CO3-doped CaO-based sorbent for CO2 capture: Performance studies and promotion mechanisms

Calcium looping (CaL) represents a promising technology for CO 2 capture from flue gas. Nevertheless, CaO-based sorbents, characterized by high theoretical absorption capacities and low costs, experience significant degradation in CO 2 capture capacity during continuous cycling. In the present study, a novel K 2 CO 3 -doped CaO sorbent was synthesized through a concurrent hydrophilic impregnation process, and the performance of consecutive cyclic CO 2 capture was evaluated. The optimal 0.05 K-CaO demonstrated the highest CO 2 sorption (12.4 mmol/g), maintaining about 64 % of the initial sorption after 20 repetitive cycles under N 2 calcination atmosphere, which is 6.6 times greater than that of CaO. These findings indicated that K 2 CO 3 can regulate the particle size and the state of surface oxygen species in CaO-based sorbents while simultaneously enhancing CO 2 diffusivity on the sorbent surface. The DFT calculations indicated that the incorporation of K 2 CO 3 improved the mechanism of CaO chemisorption of CO 2 . Additionally, the vacancies and CO 3 2– generated by K 2 CO 3 doping can enhance the CO 2 sorption energy and reduce the system’s energy level. Notably, the net charge transfer for CO 2 sorption from K 2 CO 3 doping is greater than that from pure CaO, and the O atoms on the surface of K 2 CO 3 -CaO (001) exhibit strong covalent interactions with the C atoms in CO 2 , both of which facilitate CO 2 chemisorption. This study offers a comprehensive theoretical mechanism for the incorporation of K-based alkali metals to enhance the CO 2 capture performance of CaO sorbents.