  Using ab initio methods, we examine the the charge distribution at the
interface of alpha-alumina-supported Pt films, and we consider the influence of
this interface on CO adsorption. We demonstrate that a combination of
electrostatic charge transfer and covalent bonding governs the interfacial
interactions, and that these interactions play an important role in the metal
reactivity. By modifying the interface and varying the Pt film thickness over a
nanoscale range, CO adsorption can be significantly enhanced or diminished.
These observations could be used to tune the reactivity of Pt particles.
