STM AND ESCA STUDIES OF PALLADIUM PARTICLES DEPOSITED ON A HOPG SURFACE

The preparation of palladium catalyst particles deposited by ion excha nge on the activated surface of highly oriented pyrolytic graphite (HO PG) has been investigated by STM and ESCA methods. Each step of the pr eparation procedure was characterized in a parallel way using the two techniques. After oxidation treatment of the graphite substrate chemic al oxidized functions are revealed by ESCA, while STM images indicate that both chemical and physical sites are created. Ion exchange of a p alladium salt solution with the activated carbon surface gives isolate d particles. It appeared that the preliminary oxidation treatment cond itions play an important role in the size and surface distribution of particles. These parameters are further modified by the final hydrogen reduction treatment which induces a migration of palladium which conc entrates near physical sites.