XPS investigation of surface oxidation and reduction in nanocrystalline Ce_xLa_{1 − x}O_{2 − y}

Inert gas condensation was used to generate nanocrystalline La‐doped CeO_{2 − x}. Non‐stoichiometric CeO_{2 − 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 CeO_{2 − x} was investigated through in situ oxidation‐reduction thermal treatments. Oxidation in CO₂ and reduction in H₂ atmospheres were performed between 30°C and 600°C in a reaction chamber connected to a 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.