Oxygen interaction with Pt-Pd-Rh catalytic alloys

Abstract

The effect ofmolecular oxygen interaction with Pt92.5%-Pd4%-Rh3.5% and Pt81%-Pd15%-Rh3.5%-Ru0.5% (wt%) alloy Qauzesvvasstudied. The investigation was carried out at temperatures of 1163 and 1373 K under oxygen pressure of 0.094 M Pa. Reaction of the alloys with oxygen leads to the formation of volatile oxidesα-PtO₂, RhO and PdO and to changes in the surface topography and chemical composition of the gauzes. Using atomic absorption spectroscopy, scanning electron microscopy and electron probe microanalysis methods the rate of the volatile oxide formation and the characteristics of the surface changes were determined. The rate of the oxide formation decreases with increasing palladium concentration in the alloys. The distributions of elements on the oxidized surfaces are non-uniform; grain facets are enriched with platinum and grain boundaries with rhodium and oxygen, probably in the form of Rh₂O₃. However, distinct differences in palladium distribution were not observed.