We have employed resonant photoemission spectroscopy to investigate the phenomenon of hydrogen spillover on well-defined model Pt/ceria catalysts. On Pt/CeO2(111)/Cu(111), hydrogen spillover and reverse spillover give rise to reversible changes of the oxidation state of the surface cerium ions. These changes are monitored with highest sensitivity via resonant enhancement of Ce3+- and Ce4+-related features in the valence band photoemission spectra. The temperature regions are precisely determined in which specific processes such hydrogen spillover, Ce3+ transport, and reverse spillover are activated. (C) 2011 Elsevier Inc. All rights reserved.