Synthesis of 3D-nanonet hollow structured Co3O4 for high capacity supercapacitor.

A 3D-nanonet structured cobalt-basic-carbonate precursor has been obtained by a facile, low cost and eco-friendly route under ambient temperature and pressure. After calcination in air, the as-prepared precursor was converted to a 3D-nanonet hollow structured Co3O4 with its original frame structure almost preserved. Encouragingly, by alternating experimental parameters (Table S1 in the Supporting Information ), such as concentration of the starting reagents and calcination temperature, we got the optimized condition for the final product with desirable electrochemical performance (Figure S1 in the Supporting Information ). The pseudocapacitive properties of the obtained Co3O4 were evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge measurement and electrochemical impedance spectroscopy in 6.0 M KOH solution. At different scan rates of 5, 10, 20, and 30 mV s(-1), the corresponding specific capacitances were 820, 755, 693, and 656 F g(-1), respectively. The material also exhibited superior charge-discharge stability and maintained 90.2% of its initial capacitance after 1000 continuous charge-discharge cycles at a current density of 5 A g(-1). From a broad view, our research and the outstanding results not only present a feasible access to nanostructured Co3O4 but also remind us of paying more attention to the simple synthetic methods without complex processes and sophisticated instruments.