Characterization of oxide supported rhodium nanocrystals: habit, surface structure and catalytic activity

Abstract

Well-facetted Rh nanocrystals, epitaxially grown on NaCl substrates and supported by amorphous alumina, were selected to study the effect of annealing in O 2 and H 2 on the particle microstructure and catalytic properties. The habit and the surface composition of the crystallites were determined by high resolution electron microscopy assisted by image contrast simulation, and by electron diffraction. Their catalytic performance in the hydrogenolysis of alkanes was tested by microreactor kinetics. Model catalysts with high turnover frequencies mainly exhibited Rh particles with disordered surface structures (e.g. polycrystalline Rh particles or sandwich structures of Rh and Rh 2O 3), while smooth low-index facets dominated in less active catalysts. The results confirm that low-coordinated sites are preferred for hydrogenolysis.