The interaction of Pt with CeO2 layers was investigated by using photoelectron spectroscopy. Thirty-nanometre-thick Pt and Sn doped CeO2 layers were deposited simultaneously by rf-magnetron sputtering on a Si(001) substrate and a carbon diffusion layer of a polymer membrane fuel cell by using a composite CeO2–Pt–Sn target. The laboratory XPS and synchrotron radiation soft X-ray and hard X-ray photoemission spectra showed the formation of cerium oxide with completely ionised Pt2+,4+ species, and with Pt4+ embedded in the film bulk. Hydrogen/air fuel cell activity measurements normalised to the amount of Pt used revealed high specific power of up to 5.4 × 104 mW mg–1 (Pt). The activity of these materials is explained by the strong activity of embedded Ptn+ cations.