Copper-Cerium Oxide Catalysts for CO Oxidation : An EXAFS and XRD Study

Abstract
Mixed copper-cerium oxides were prepared by two methods leading to different copper species in the as-prepared material. At the catalyst operating temperature (300-400°C) and above, the same copper species was present irrespective of the preparation technique. A solid solution having the same fluorite structure as that of pure CeO₂ was formed and remained stable after calcination to 1000°C. At temperatures in excess of 600°C the formation of a CuO phase was also noticed. Catalytic activity of the mixed copper-cerium oxides for the oxidation of CO to CO₂ proved very favourable even under O₂ poor conditions. Activity decreasesd with increasing calcination temperature as the material sintered and lost surface area, and the copper species deactivated through formation of CuO. The importance of EXAFS as an analytical tool in ascertaining the nature of the copper species at the catalyst operating temperature was highlighted.