A STUDY OF METAL-SEMICONDUCTOR CATALYST, HYDROGEN SPILLOVER ON Pt/SnO2 AT ROOM TEMPERATURE

Hydrogen spillover and its effect on Pt/SnO2 has been studied in comparison with carbon-monoxide. The catalyst used was prepared by impregnation. The experiments of H-2-O-2 cycle pulse titration and reaction of H-saturated Pt/SnO2 with O-2 evidently illustrated that hydrogen adsorbed on Pt/SnO2 can migrate from Pt to platinized SnO2 freely even at room temperature. Studying the behaviour of unplatinized SnO2 mixed with Pt/SnO2, we have shown the occurence of secondary hydrogen spillover, i.e., the spillover hydrogen can migrate from Pt/SnO2 particles to bare SnO2 particles as well. It is demonstrated that while the catalyst surface exerts actions on the adsorbed molecules activating them, the adsorbates make a re-action on the catalyst in turn. By the electrical conductance measurement and Mossbauer spectra, it is revealed that the hydrogen migrating to SnO2 from Pt interacted with SnO2. The electron of spillover hydrogen transfered to the conduction band of semiconductor SnO2, Causing an increase in the electrical conductance of SnO2, and resulting in partial reduction of Sn4+. At a little higher temperature, the concentration of low-valence tin was high enough to be detected by Mossbauer spectra.