Adsorption of carbon dioxide on Al12X clusters studied by density functional theory: effect of charge and doping

The adsorption of a CO2 molecule on neutral and charged X-centered icosahedron Al12X(±z) clusters (X = Al, Be, Zn, Ni, Cu, B, P; z = 0, 1) was investigated by the density functional PW91 and PWC methods. Optimized configurations corresponding to physisorption and chemisorption of CO2 were identified. The adsorption energies, activation barriers, and binding energies involving both the physisorption (Al12X(±z)·CO2-I) and chemisorption (Al12X(±z)·CO2-II) for CO2 were determined. The chemisorption of a CO2 molecule on the Al12X clusters (X is a metallic doping element) requires relatively low activation barriers. The lowest barrier was found to be with the Al12Be cluster. For the Al12X(-) clusters, the barriers are all higher than those of the neutral analogues. For the Al12X(+) clusters, two corresponding configurations are linked by a low-energy barrier, and CO2 molecule chemisorption on the Al12Be(+) cluster has the lowest barrier. The adsorption energies are larger than the energy barriers, which facilitates the chemisorption. The results show that carbon dioxide adsorbed on the Al12X(±z) clusters can be tuned by controllable X doping and the total number of valence electrons and suggest the potential application of Al12X(±z) nanostructures for carbon dioxide capture and activation.