The influence of surface roughness on ISS analysis of supported catalysts

Abstract

Abstract The atomic surface structure of real and model catalysts is often analysed on a monolayer scale by various surface analytical techniques, in particular ion scattering spectroscopy (ISS). The question to which extent the surface roughness influences these studies has been tackled by investigating a series of A12O3 samples, the roughness of which ranges from polished single crystal sapphire surfaces to pressed powder wafers. By anodically oxidizing Al sheets under different conditions, various intermediate states of surface roughness have been produced. The ISS results show that the absolute intensity in the scattering peaks decreases strongly with increasing surface roughness. However, the relative intensities of the surface components (e.g. Al, O, and Mo from adsorbed molybdate) remain rather unchanged. Therefore, the conclusions appear to be justified that with respect to these results ISS provides valid composition ratios also for rough powder samples and that plane model catalyst studies bear relevance for the description of real catalyst systems.