Effect of Microwave on the Nanowire Morphology, Optical, Magnetic, and Pseudocapacitance Behavior of Co3O4

In the context of immense control of synthesis methods on the structural and functional characteristics of the materials, nanowire morphologies of Co3O4 are synthesized in conventional reflux and microwave-assisted methods, under homogeneous precipitation conditions. The Co3O4 sample synthesized by the conventional reflux method consists of randomly distributed thin nanowires while the microwave reflux method generates higher-dimensional and arranged Co3O4 nanowires. The surface area and pore structural analysis of the Co3O4 samples show significant difference in their meso- and macroporosity as well as specific surface area, due to differently crystallized products. The UV-Vis-DRS study shows crystallite size dependent optical transitions and band gaps. The magnetic study illustrates finite size effect and low temperature ferromagnetism in both samples; the lower-dimensional nanowires being more ferromagnetic than the higher-dimensional Co3O4 nanowires. Due to smaller crystallite size and more accessible surface sites, the Co3O4 sample synthesized by the conventional reflux method shows better charge storage, high Coulombic efficiency, and enhanced rate response during the pseudocapacitance studies. However the Co3O4 sample synthesized using the microwave-assisted method shows better high rate cyclic stability due to its more rigid orientated nanowire structure. Further, the Ragone plot exhibits considerably higher energy and power densities of lower-dimensional Co3O4 nanowires. Broadly, this study reveals that, under nonhydrothermal homogeneous precipitation conditions, the conventional reflux synthesized lower-dimensional Co3O4 nanowires bear superior surface properties than the microwave synthesized higher-dimensional Co3O4 nanowires, for electrochemical supercapacitor applications.