Effect of mild re-oxidation treatments with CO2 on the chemisorption capability of a Pt/CeO2 catalyst reduced at 500 degrees C

By combining FTIR spectroscopy of chemisorbed CO and HRTEM, we have studied the evolution undergone by the metal chemisorption capability and nanostru ctural properties of a Pt/CeO2 catalyst reduced at increasing temperatures from 200 to 500 degreesC, As revealed by the nu (CO) integrated absorption data on Pt, a progressive metal deactivation is observed. The analysis of t he HRTEM micrographs allows us to exclude metal sintering, decoration, and Pt-Ce alloying phenomena as the likely origin of the observed effect, If th e catalyst reduced at 500 degreesC is further heated under CO2 (300 Torr), at a very mild temperature, 200 degreesC, its chemisorption capability is p artly recovered. This regeneration effect is interpreted as due to the Pt-a ssisted CO2 re-oxidation of the ceria support with inherent chemisorption o f the resulting CO on the metal microcrystals. These observations are consi stent with the model recently proposed by our laboratory on the nature of t he strong metal-support interaction phenomena occurring in NM/CeO2 catalyst s. (C) 2001 Academic Press.