Platinum-oxide nanoparticles were prepared through the radio-frequency (RF) discharge sputtering of a Pt electrode in an oxygen atmosphere. The structure, particles size, electronic properties, and surface composition of the RF-sputtered particles were studied by using transmission electron microscopy and X-ray photoelectron spectroscopy. The application of the RF discharge method resulted in the formation of highly oxidized Pt4+ species that were stable under ultrahigh vacuum conditions up to 100°C, indicating the capability of Pt4+-O species to play an important role in the oxidation catalysis under real conditions. The thermal stability and reaction probability of Pt4+ oxide species were analyzed and compared with those of Pt2+ species. The reaction probability of PtO2 nanoparticles at 90°C was found to be about ten times higher than that of PtO-like structures.