One-pot fabrication of Co3O4 microspheres via hydrothermal method at low temperature for high capacity supercapacitor

• Take full advantage of the easily oxidized feature of cobalt (II) complexes ammonia.
• Low temperature method was applied with absence of subsequent calcination process.
• The Co3O4 microspheres possess extraordinary electrochemical properties.

Co3O4 microspheres were successfully produced with one-step low temperature hydrothermal method and their electrochemical properties have been investigated. By means of utilizing easily oxidized characteristic of cobalt complexes ammonia, the Co3O4 microspheres were synthesized for the first time with an extremely low hydrothermal temperature (100 °C). In the absent case of surfactant, these Co3O4 microspheres with a diameter of ca. 500 nm and smooth surface were prepared with the assistance of nitrate. Influences concerning about temperature and concentration of nitrate on morphology and size distribution were thoroughly discussed. Electrochemical characterization indicated that the Co3O4 microspheres exhibited high specific capacitance of 850, 780, 700, 630 F/g at current densities of 1, 2, 4, 8 A/g, respectively. And after 1000 cycles, the devices with Co3O4 microspheres showed high charge/discharge reversibility with an efficiency of 90.8% at a current density of 2 A/g.