Reduction of thin-film ceria on Pt(111) by supported Pd nanoparticles probed with resonant photoemission

► We use resonant photoemission to show that Pd nanoparticles reduce an ultrathin CeO2(111) film. ► The resonant photoemission data are in qualitative agreement with XPS results on the same surface. ► Earlier calculations suggest that the reduction of the film arises from charge transfer from Pd to the film.