Preparation and characterization of ultrafine cobalt powders and supported cobalt catalysts by freeze-drying

Ultrafine cobalt powders have been prepared by the freeze-drying method and supported cobalt catalysts have been prepared by a new freeze-drying immersion method. The results of XRD and SEM showed that the precursors were amorphous and most were massive with a size range of 2–5 µm. In the cobalt powders synthesized by freeze-drying, the grains were spherical in shape and with sizes ranging from 30 to 50 nm. IR analysis showed that Co existed in the precursor in the form of [Co(NH3)x]2(C2O4)3. EDS line scanning results indicated that catalysts prepared by freeze-drying could load more cobalt powders and the distribution was more homogeneous. Catalyst activity was also tested in the system of carbon monoxide oxidation. The catalysts in this research can lower the ignition temperature of CO and have increased catalytic properties.