Investigating the microscopic enhancement mechanisms of adsorption-based CO2 capture with Cu-loaded γ- Al2O3 using density functional theory

Transition-metal-loaded gamma-alumina (Al2O3) is considered to be an effective adsorbent for CO2 capture, but its microscopic process and mechanisms of CO2 adsorption are not fully understood. To investigate the microscopic enhancement role of Cu atoms in CO2 adsorption, this work compares various adsorption configurations and parameters of CO2 on gamma- Al2O3 (110) facets with or without Cu atoms and small Cu cluster loading (Cun (n_1,2,3)/ gamma- Al2O3) using the first-principles approach. According to the adsorption energy, charge transfer, difference charge density, and other parameters of different configurations, the gamma- Al2O3 (110) slab loaded with the Cu atom is found to exhibit enhanced adsorption of CO2 molecules compared to that without Cu loading. Moreover, the surface stability increases with the number of loaded Cu atoms. However, the hydroxyl groups in the active sites partially undermine the adsorption effect during the CO2 adsorption process. The density of states indicates that the doping of Cu atoms in the system creates an orbital peak closer to the Fermi energy level. This facilitates the transfer of charge within the slab, making the activation of CO2 easier and promoting stable adsorption. Finally, the amount of crystal orbital overlap population and crystal orbital Hamilton population shows that the stability of adsorption is due to the formation of C-Cu and C-Al bonds. It is demonstrated that the Cun-loaded gamma- Al2O3 (110) slab improves the adsorption performance and contributes to a better understanding of the effect of transition-state metal loaded gamma- Al2O3 on CO2 adsorption.