Abstract
Cerium 4f level occupation determines the properties of cerium oxide based catalysts in a significant way. Photoelectron spectroscopy is a powerful tool for investigating Ce 4f states, and there are many spectroscopic data showing different 4f configurations using Ce 3d spectra.
Resonance spectroscopy permits the determination of 4f state occupation in ceria based compounds with very high sensitivity. In this work the Ce 4f level of nanosized cerium oxide particles was investigated with the use of resonant photoelectron spectroscopy in the Ce 4d-4f photoabsorption region at photon energies hny around 121.5 and 124.5 eV.
A strong interaction of ceria with different additives, e.g. Pd and Sn, led to a partial Ce4 Ce3 transition that was observed as a significant resonance enhancement of 4f photoemission intensity.
Increases of the CO oxidation catalytic activity were observed simultaneously.