Promotional effects and reconstruction of Pt/CeOx, and Pt/SiO2 model catalysts produced by electron-beam lithography (EBL)

We have studied the activity and stability of EEL-fabricated Pt/CeOx and Pt /SiO2 supported model catalysts during catalytic reactions. Different mixtu res of H-2 + O-2 diluted in argon and CO + O-2 diluted in argon have been u sed in the temperature range 300-475 degreesC. Reaction-induced morphology changes are observed for both types of samples after heat treatments in mix tures of H-2 + O-2 diluted in argon. The EEL-fabricated samples are stable for reproducible CO oxidation measurements for at least a period of 50 h at 400 degreesC. Pre-reduction at 400 degreesC is shown to be favorable for C O oxidation in rich mixtures for the EEL-fabricated Pt/CeOx catalyst, while the opposite is measured for the EEL-fabricated Pt/SiO2 catalyst. Two powd er samples, Pt/CeOx and Pt/SiO2, have also been tested during similar pre-t reatment studies. Increased activity for CO oxidation (rich conditions) is found for both types of samples after pre-reduction, compared with pre-oxid ation. (C) 2001 Academic Press.