Coverage of palladium by silicon oxide during reduction in H 2 and complete oxidation of methane

Abstract

The interaction between silica and palladium following complete oxidation of methane or following reduction in H 2 was investigated on a polycrystalline palladium foil and on supported Pd/SiO 2 catalysts. During methane oxidation, oxidized silicon covered the palladium oxide surface as observed by TEM on Pd/SiO 2 catalysts and by XPS on palladium foil. On the Pd foil, the source of silica was a silicon impurity, common on bulk metal samples. The migration of oxidized silicon onto PdO deactivated the catalysts by blocking the active sites for methane oxidation. Silicon oxide overlayers were also observed covering the Pd surface after reduction of Pd/SiO 2 by H 2 at 923 K.