Syntheses of Nanostructures of Cobalt Hydrotalcite Like Compounds and Co3O4 via a Microwave-Assisted Reflux Method

An efficient microwave-assisted reflux route has been used to synthesize layered nanostructures of cobalt hydrotalcite like compound spheres. Scanning electron microscopy images showed that these structures are self-assemblies of the nanosheets with uniform 5-nm thickness. The layered cobalt hydrotalcite like compound has high surface area and large pore volume, which are 176 m2/g and 1.13 m3/g, respectively. These cobalt hydrotalcite like compounds can transfer into the spinel structure of Co3O4, which keeps a uniform spherical shape. Surface area and pore volume of the Co3O4 are 61 m2/g and 0.5 cm3/g, respectively. Both materials show electrocatalytic activity and stability for the electrochemical reduction of oxygen. High surface area of these catalysts correlates with high rates of electrochemical reduction of oxygen. Therefore, these materials have potential as electrocatalytic materials or as noble metal catalyst supports. This efficient route is also used to synthesize other porous transition metal oxides such as manganese oxide, nickel oxide, and others.