High-resolution electron microscopy of metal-intercalated "Graphimets"

Samples of some commercially available catalysts (known as "Graphimets"), in the form of graphite which had been intercalated with chlorides of Fe, Co, Cu, Ni, and Pt and subsequently reduced at low temperatures, have been examined by high-resolution electron microscopy and other techniques. The observations revealed that the intercalated element was present primarily as small islands of either metal or metal oxide on the surfaces of thin graphite flakes which appeared to have separated as a consequence of the manufacturing procedure. The direct resolution of lattice fringes in electron micrographs of the small (10-100 Å) particles, together with subsequent optical diffraction, provided a means of microdiffraction analysis which enabled identification of the phases present. The very high reaction rate measured for graphite gasification in the case of the Fe Graphimet, which will be described in detail elsewhere, was in keeping with the small particle size and the correspondingly large surface area. Finally, the potential of electron microscopy at the lattice resolution level for resolving a number of outstanding questions concerning the role of small metal particles in catalysis is briefly discussed.