Predicting experimental signatures for the oxidation of magnesia supported palladium clusters by density functional theory

We showed in a recent density functional study that small palladium cluster on a MgO surface with F-centers can be oxidized to epitaxial PdxOy nano-oxides below room temperature [1]. Here, we employ density functional theory in order to explore different methods for an experimental verification of the PdxOy formation. The electronic density of states (DOS) of bare, O-2-decorated and of oxidized palladium cluster was calculated. For many cluster sizes a clear difference in the DOS could be observed allowing for a detection of the oxidation with surface sensitive spectroscopic methods. In addition, adsorption sites and stretch frequencies of a single CO molecule on bare and oxidized Pd-4 clusters were calculated. While CO prefers hollow sites on Pd-4, top adsorption sites are found for Pd4O2. Markedly different CO stretch frequencies indicate a possible discrimination of bare clusters and oxides by Fourier transform infrared spectroscopy.