Mechanistic Aspects of N2O Formation Over Pt-Based Lean NOx Trap Catalysts

In this paper mechanistic aspects on the formation of N2O over a model Pt–Ba/Al2O3 NOx storage and reduction catalyst are investigated. The data indicate that N2O formation involves the coupling of N-adspecies with undissociated NO molecules: accordingly this requires the presence of partially reduced Pt sites, to catalyse the NO dissociation into N- and O-adspecies on one side and to prevent complete NO dissociation on the other side. In fact N2O formation is observed at temperatures where the reductant leads to a partial reduction of the Pt sites, at increasing temperatures in the order CO > NH3 > H2.