Carbon monoxide binding states over SnO2 and Pt(l%)/SnO2

Abstract

Carbon monoxide binding states on SnO₂ and Pt/SnO₂ have been investigated using thermal desorption spectroscopy(TDS). A fourier transform infrared spectrophotometer is attached with TDS for simultaneous analysis of evolved gases. Whereas a TDS profile subsequent to room temperature CO adsorption on SnO₂ consists of a single broad band with maximum at 450K, corresponding spectrum from Pt/SnO₂ consists of two overlapping peaks with maxima at around 390 and 470K. IR analysis shows that for Pt/SnO₂, the 390K peak is mainly due to CO release whereas CO₂ is the main component of 470K-peak. On the other hand, the desorption profile from SnO₂ consists of both CO and CO₂ in entire temperature range. The shape of a TDS profile and the relative yield of CO and CO₂ at a particular sample temperature depends on the pretreatment given to sample prior to CO adsorption. The delineation of individual roles of metal and support in CO oxidation over Pt/SnO₂ is attempted on the basis of these results.