Cluster and periodic ab initio calculations on the adsorption of CO2 on the SnO2(1 1 0) surface

The interaction of CO2 with the Sn cations and the bridging oxygen anions sites of the SnO2(1 1 0) 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.