Density Functional Theory Investigation of Adsorption Properties of CO, CO$_2$ and H$_2$O on $\gamma$-Al$_2$O$_3$ Supported Pt Clusters*

The water-gas shift reaction is a key catalytic process for the production of clean H$_2$ gas for fuel cells.\footnote{M. S. Dresselhaus and I. L. Thomas, Nature 414, 332 (2001)} In this study, we use plane wave pseudopotential density functional theory to study the adsorption properties and the activation of CO, CO$_2$ and H$_2$O on Pt clusters supported on the (001) surface of $\gamma$-Al$_2$O$_3$. A systematic study has been conducted to identify the most stable adsorption sites for both monoatomic and diatomic Pt clusters. Several stable adsorption geometries have been identified for the adsorbates, and their interaction with both the precious metal and the support is characterized in terms of adsorption energies and the nature of the bond between the adsorbed molecules and the precious metal.