The role of metal-support interaction on the oxidation of noble metals supported on cerium based oxides

摘要

A HREM investigation of the oxidation process, under pulsing 5%O_2/He, of a 0.5% Rh/Ce_(0.8)Tb_(0.2)O_(2-x) catalyst has been performed. HREM images obtained after oxidation in the temperature range 573K - 773K indicate the transformation of the Rh metal particles into the low pressure, high temperature orthorrombic polymorph of Rh_2O_3. These oxide particles are grown under well defined orientation relationships onto the support. These relationships have been interpreted on the basis of an original correlation established between the structure of the f.c.c. metal phase, the orthorrobic sesquioxide and the fluorite-type support.