Study of active surface centers of Pt/CeO2 catalysts prepared using radio-frequency plasma sputtering technique

RF-plasma deposition of Pt on a nanosized ceria powder support has been performed directly in photoelectron spectrometer chambers to prepare model catalysts. The plasma deposition in an oxidizing environment results in the formation of highly dispersed oxide nanoparticles up to 2 nm large, which contain platinum solely as Pt4+ ions revealed by Eb(Pf4f7/2) = 74.6 eV. Thus prepared model catalyst samples arranged as (sub-monolayer) films of PtO2 nanoparticles on the surface of CeO2 are characterized by an increased thermal stability compared with PtO2 nanoparticles deposited on more inert supports. These PtO2/CeO2 model catalysts show a high activity in the CO oxidation even at room temperature. A detailed analysis of the O1s spectra obtained during the titration by CO of PtO2/CeO2 films strongly suggests that the reactive oxygen species are manifested with Eb(O1s) = 530.8 eV and 532.9 eV. The latter core level energies are attributed to oxygen in the platinum dioxide and to peroxide-like oxygen, presumably located at the interface between PtO2 and CeO2 particles. Results of our density-functional calculations indicate that the peroxide-like species can be energetically stabilized at the PtOx–CeO2 interfaces.