Reduction of thin-film ceria on Pt(111) by supported Pd nanoparticles probed with resonant photoemission |
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Authors: | J Matharu G Cabailh R Lindsay CL Pang DC Grinter T Skála G Thornton |
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Institution: | 1. London Centre for Nanotechnology and Chemistry Department, University College London, 20 Gordon Street, London, WC1H 0AJ, UK;2. Corrosion and Protection Centre, School of Materials, The University of Manchester, Sackville Street, Manchester, M13 9PL, UK;3. Sincrotrone Trieste, Strada Statale 14, km 163.5, 34149 Basovizza-Trieste, Italy |
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Abstract: | Local defects present in CeO2 ? x films result in a mixture of Ce3+ and Ce4+ oxidation states. Previous studies of the Ce 3d region with XPS have shown that depositing metal nanoparticles on ceria films causes further reduction, with an increase in Ce3+ concentration. Here, we compare the use of XPS and resonant photoemission spectroscopy (RESPES) to estimate the concentration of Ce3+ and Ce4+ in CeO2 ? x films grown on Pt (111), and the variation of this concentration as a function of Pd deposition. Due to the nature of the electronic structure of CeO2 ? x, resonant peaks are observed for the 4d–4f transitions when the photon energy matches the resonant energy; (hν = 121.0 eV) for Ce3+ and (hν = 124.5 eV) for Ce4+. This results in two discrete resonant photoemission peaks in valence band spectra. The ratio of the difference of these peaks with off-resonance scans gives an indication of the relative contribution of Ce3+. Results from RESPES indicate reduction of CeO2 ? x on deposition of Pd, confirming earlier findings from XPS studies. |
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