Hollow Co3O4 microspheres with nano-sized shells: one-step large-scale synthesis, growth mechanism and supercapacitor properties

Hollow Co3O4 microspheres with thin spherical shells were produced using a one-step method at a low hydrothermal temperature (120 degrees C), and could be obtained without the use of a solid template, organic reagent or subsequent calcination. These hollow Co3O4 microspheres possess a diameter of ca. 500 nm and a thin shell thickness of ca. 50 nm. The samples were characterized by field emission scanning electron microscope (SEM), transmission electron microscope (TEM) and powder X-ray diffraction (PXRD). A multistep-splitting growth mechanism was proposed to reveal the formation of hollow Co3O4 microspheres. The successful fabrication of the hollow spherical morphology of these microspheres highlighted the importance of H2O2 dosage and the nitrate concentration. Electrochemical performance tests of the as-prepared samples indicated that the hollow Co3O4 microspheres exhibited ultrahigh specific capacitances of 1227, 1169, 1116, 1035 F g(-1) at current densities of 1, 2, 4, 8 A g(-1), respectively. After 1000 cycles, the specific capacitance of hollow Co3O4 microspheres showed high charge-discharge reversibility and only a slight decay of less than 3% at a current density of 2 A g(-1).