Characterization of carbon supported catalysts by electron microscopy techniques

A series of mono- and bimetallic catalysts supported on carbon was prepared and characterized by different electron microscopy techniques. Support morphology, size and distribution of the metal active phase of monometallic samples of Pt and Ru were obtained by SEM and TEM. Addition of tin changed the size and morphology of the metal particles in a different way, depending on the noble metal considered. Microstructural characterization of these individual metal particles was performed by HREM. Fourier transform analysis and image simulations were employed to help in interpretation of the HREM images. Mainly the f.c.c structure of platinum and h.c.p structure of ruthenium were found. However, on samples with a high tin content, a few particles of Me-Sn alloy have been detected. Adsorption of N-2 and CO was also used to obtain additional information on the catalytic system. The characterization results reported help to understand the remarkable catalytic properties of these bimetallic catalysts in selective hydrogenation reactions.