XPS INVESTIGATION OF SURFACE OXIDATION AND REDUCTION IN NANOCRYSTALLINE CEXLA1-XO2-Y

Inert gas condensation was used to generate nanocrystalline La-doped CeO2-x. Non-stoichiometric CeO2-x-based materials were found to be excellent catalysts in recent studies for the selective reduction of SO2. To understand better the stoichiometry-related catalytic properties, the surface chemistry of nanocrystalline La-doped CeO2-x was investigated through in situ oxidation-reduction thermal treatments. Oxidation in CO2 and reduction in H-2 atmospheres were performed between 30 degrees C and 600 degrees C in a reaction chamber connected to an x-ray photoelectron spectrometer analytical chamber. Curve fitting and target factor analysis were used to obtain a semi-quantitative measurement of the transformation between +3 and +4 oxidation states during these reactions. Target factor analysis was found to be a very useful tool for analyzing the contributions corresponding to Ce+3 and Ce+4.