MgO-Supported Rhodium Particles and Films: Size, Morphology, and Reactivity

The chemical transformations of supported Rh particles, ranging in size from a few micrometers to a few nanometers, and nanocrystalline Rh films have been studied under identical oxidizing and reduction conditions by means of scanning photoelectron microscopy (SPEM), which allows determination of the chemical state of single Rh microparticles. Comparing the oxidation states attained by the Rh particles revealed substantial reactivity differences with particle size, as well as variations in the reactivity of particles with similar dimensions and within the same particle. The results are interpreted in terms of the variable morphology of the particles as verified by secondary electron microscopy and atomic force microscopy.