Adsorption of CO₂ Molecule on the (MgO)₉ and (CaO)₉ Nanoclusters; A Theoretical Study

Binding configurations of CO₂ on (MgO)₉ and (CaO)₉ cluster models are investigated by means of density functional theory model calculations. The results show that CO₂ adsorbs as monodentate on MgO and CaO terrace site leads to formation of surface carbonates CO₃^2-. Marginal differences in the binding stabilities between the CO₂ molecule and surface O^2-site were found to be significantly similar. The estimated adsorption energies are 1.47 eV and 1.52 eV at the (MgO)₉ and (CaO)₉ clusters, respectively. The similarity in binding energies is discussed in terms of cluster electro positivity. Adsorbed CO₂, to (MgO)₉ surface vibration frequencies are calculated and compared to the experiment.