Cluster and periodic ab initio calculations on the adsorption of CO2 on the SnO2(110) surface

The interaction of CO2 with the Sn cations and the bridging oxygen anions sites of the SnO2(110) surface has been investigated by means of gradient corrected density functional theory calculations and cluster models and periodic slabs. CO2 interacts electrostatically with the five-coordinated Sn cations; the molecule is bound with the molecular axis perpendicular to the surface and is slightly distorted compared with the gas-phase molecule, On the bridging oxygen anions and in the limit of zero coverage. CO2 is chemisorbed with the formation of a surface carbonate; the process, however, is almost thermoneutral and the chemisorbed state is metastable. As the coverage increases, the adsorbate-adsorbate repulsion make the formation of chemisorbed CO2 unfavorable. The non-defective SnO2 surface exhibits therefore very little reactivity towards CO2.