Strengthened CO2 adsorption over Ce/Al-promoted MgO for fast capture

Abstract

Big transition state (TS) energy barriers of free-state CO2 molecules getting adsorbed on different sites of MgO are one of the most difficult issues to accomplish fast CO2 adsorption. In order to solve this problem, cerium (Ce) atoms are used as a dopant to modify MgO’s surface potential fields with the purpose of quicker CO2 adsorption processes. In this study, TS processes of CO2 getting adsorbed on pure, Ca-doped, Fe-doped and Al-doped MgO are firstly investigated to analyze the relationship between TS processes and TS energy barriers. Since Al-doped MgO shows the best compromise feature in the relationship, thus, Ce is adopted as single-atom promoters to facilitate CO2 adsorption processes over Al-doped MgO. According to density functional theory (DFT) calculations, the average TS energy barrier of CO2 adsorption over Ce/Al-doped MgO is nearly reduced to 0 with 146.82% bigger average adsorption energy in contrast with Al-doped MgO. What is more, effects of temperatures on CO2 adsorption traits and adsorption kinetics of different TS processes are explored to reflect promotion effects of single-atom Ce. The relevant consequences present that doping of Ce atoms could simultaneously reduce the activation energy by 74.74% and improve the temperature power exponent by 0.11%. The whole results of this study would supply crucial information for stable/fast CO2 adsorption over MgO-based adsorbents in industries.