Model sulfur-resistant NSR catalysts: An XPS study of the interaction of BaO/TiO2-ZrO2 and Pt-BaO/TiO2-ZrO2 with NO2

The interaction of NO2 with BaO/TiO2-ZrO2 and Pt-BaO/TiO2-ZrO2 model NOx storage-reduction (NSR) catalysts prepared on the surface of FeCrAl alloy substrates has been investigated by X-ray photoelectron spectroscopy. The action of nitrogen dioxide on these catalysts at room temperature causes the consecutive formation of surface barium nitrite and nitrate. Supposedly, NO2 reduction yielding barium nitrite at the early stages of the interaction is due to the oxidation of amorphous carbon impurities. The introduction of platinum into the catalyst accelerates nitrogen dioxide sorption. On being exposed to NO2 for a long time, platinum oxidizes to PtO2. This process is more pronounced in the sample containing freshly deposited platinum. Heat treatment of this sample in a vacuum, which coarsens the platinum particles, makes them more resistant to oxidation.