Pd/SnO₂ and Pt/SnO₂ catalysts : Spillover effects

Abstract

Results of ¹¹⁹Sn Mossbauer spectroscopy are reported for Pd/SnO₂ and Pt/SnO₂ catalysts. Direct evidence in support of the spill over of hydrogen and carbon monoxide from metal sites to SnO₂ support is provided by Mossbauer spectroscopic measurements of Pd/SnO₂ and Pt/SnO₂ catalysts. The support SnO₂ and metal impregnated SnO₂ samples have been treated under identical conditions of H₂ or CO flow and their Mossbauer spectra recorded at room temperature. The formation of Sn²⁺ state is clearly revealed for all these samples; the extent of Sn²⁺ formation is a function of metal content and gas treatment conditions. The spill over of oxygen from metal to support oxide has not been observed in this study. The S²⁺ species are characterised by isometric shift <img src='/image/spc_char/delta1.gif' border=0> <img src='http://www.niscair.res.in/jinfo/tiled1.gif' border=0> 2.9 mm/sec and quadrupole splitting <img src='/image/spc_char/delta.gif' border=0>Eq <img src='http://www.niscair.res.in/jinfo/tiled1.gif' border=0> 1.9 mm/sec which suggest the formation of SnO.