Surface chemistry of catalyst preparation studied by using flat alumina model supports

Abstract

Rhodium on alumina model catalysts have been made by using a flat, electrically conducting support consisting of a thin film of aluminum oxide on an aluminum foil. Rhodium was applied in the same way as is usual in the preparation of powder catalysts, by adsorption from an aqueous solution of rhodium (III) chloride. The catalysts were studied with monochromatic x-ray photoelectron spectroscopy (XPS), static secondary ion mass spectrometry (SIMS), and Rutherford backscattering spectrometry (RBS). Because the systems have electrical conductivity, XPS spectra of high resolution are obtained while informative molecular clusters of the type RhCl− and RhO−n appear in static SIMS. Angle-dependent XPS spectra of Rh and Al yield an effective layer thickness of Rh, as well as the extent to which the support is covered. RBS indicates that the Rh concentration is in the order of 1015 atoms/cm2.