Influence of the adsorption of CO on the electronic structure of platinum clusters and nanowires deposited on CeO2(111) and γ-Al2O3(001) surfaces

Using periodic density functional calculations we clarified the variations of the electronic structure of platinum clusters and nanowires upon their deposition on reducible and on non-reducible oxide as well as upon adsorption of carbon monoxide. Three models of platinum clusters and nanowires deposited on ceria surface and one on gamma-alumina surface were studied. At high CO coverage, when the metal cluster or nanowire is completely covered by CO, there is clear depletion of the occupied Pt 5d-projected states close to the Fermi level and appearance of a new state at lower energies, in the region around -1.5 eV below the Fermi level. Thus, in total the 5d states are stabilised and the d-band center in all systems shifts to lower energies, which is an indication that the reactivity of the platinum clusters decreases upon adsorption of carbon monoxide. According to the calculated d-band center value, the metal cluster on gamma-alumina is the most reactive (in terms of electron-donating properties) as its d-band center is located at higher energy compared to platinum on ceria. For most of the models the most stable adsorption position of CO is linear to a platinum atom from the upper part of the platinum moiety, while for the largest model the most stable position is bridging between two platinum atoms.