In situ XPS study of the size effect in the interaction of NO with the surface of the model Ag/Al2O3/FeCrAl catalysts

Abstract

The interaction of NO with the surface of model Ag/Al2O3/FeCrAl catalysts containing Ag nanoparticles of different size (1 and 3 nm) was studied. The use of the Auger parameter αAg (E b(Ag3d5/2) + E kin(Ag MVV)) made it possible to reliably identify the change in the chemical state of silver cluster upon their interaction with О2 and NO. The oxygen treatment leads to the oxidation of small Ag nanoparticles (1 nm) and formation of AgO x clusters resulted in the intensive formation of nitrite—nitrate structures on the step of the interaction with NO. These structures are localized on both the silver clusters and Al2O3 surface. An increase in the size of Ag0 nanoparticles to 3 nm results in an increase in the stability of these structures and impedes the Ag0 → AgO x transition, due to which the formation of surface groups NO2 –/NO3 – is suppressed. The data obtained make it possible to explain the dependence of the activity of the Ag/Al2O3 catalysts in the selective reduction of NO on the Ag nanoparticle size.