IR STUDY OF NO REDUCTION BY CO ON PT/ZNO CATALYSTS

An FTIR study of the NO-CO interaction, from RT up to 533 K, was done on two differently pretreated Pt/ZnO samples: the first, mildly reduced, formed of small pure Pt particles dispersed on ZnO, and the second, strongly reduced, presenting PtZn alloyed metal particles. On the mildly reduced one by heating in NO-CO atmosphere at 373 K a quite strong band assigned to an isocyanate species is formed, produced by reaction of CO molecules with nitrogen atoms, coming from the NO decomposition. At the same time the intensity of the CO band grows up to that of the virgin sample, showing that the isocyanate species spill over from the metal to the support. On strongly reduced samples the isocyanate species band is quite weak and a CO2 band is produced. The different behaviour will be discussed taking into account the different surface composition and electronic properties of the two samples.