Supported transition metal particles are often used as heterogeneous catalysts. Elemental mapping with energy-filtered transmission electron microscopy (EFTEM) offers distinct advantages over conventional TEM and x-ray analysis for these systems. Thickness maps, metal identification, support identification, and direct imaging of oxide layers all represent key new information made possible with EFTEM. Energy-filtered transmission electron microscopy with an omega filter has been used to show Ni, Cu and Cr distributions in an alumina-supported catalyst. in this paper we look at analogous cobalt particles from a colloidal suspension supported on a carbon film.
Energy-filtered TEM maps were obtained using a Gatan Image Filter at 200 kV integrated with an FEI CM200FEG microscope. The colloidal cobalt particles have a nominal diameter of 10 nm, providing an excellent model system when supported on thin amorphous carbon supports. Figures 1 - 3 show cobalt L23, oxygen K and elastic micrographs of partially oxidized cobalt particles (native oxide present after drying).