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

Abstract

Hollow Co₃O₄ microspheres with thin spherical shells were produced using a one-step method at a low hydrothermal temperature (120 °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.