Liquid precipitation synthesis of Co3O4 for high-performance electrochemical capacitors

The amorphous Co3O4 nanostructure, which adopted sodium hexametaphosphate as structure-directing agent, has been successfully synthesized in large scale via two steps: preparation of the precursor and the calcination process. The results of X-ray diffraction indicate that the prepared materials are mainly composed of Co3O4; the formless Co3O4 nanoplate with loose structures is observed by scanning electron microscopy. Cyclic voltammetry, chronopotentiometry, and electrochemical impedance measurements are applied in a mild aqueous electrolyte (2 mol L−1 KOH) to investigate the performance of the Co3O4, which show a high specific capacitance (SC) of 482.61 F g−1 at 5 mA cm−2. Besides, the SC degradation is only 10.05 % after 250 continuous charge–discharge cycles at 5 mA cm−2, indicating an excellent electrochemical stability. The improved performance is reasonably ascribed to their irregular structure for ionic transport during the electrochemical reaction, which presents as promising candidates for supercapacitors.