Novel morphologic Co3O4 of flower-like hierarchical microspheres as electrode material for electrochemical capacitors

Novel flower-like Co3O4 hierarchical microspheres (HMs) with high porosity were synthesized via a facile hydrothermal strategy and template-free method. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM), and nitrogen adsorption–desorption at 77 K. The results showed that so formed three dimensional (3D) hierarchical microspheres consist of numerous 2D Co3O4 nanosheets (NSs) with random attachment and have a large surface area of 115m2 g−1. The pseudocapacitive behaviors of Co3O4 HMs were investigated by cyclic voltammograms, galvanostatic charge–discharge test and electrochemical impedance spectroscopy in 3.0 M KOH solution. The results revealed that the new Co3O4 HMs delivered a large specific capacitance of as high as 541.9 F g−1 and 483.8 F g−1 at 5 mV s−1 and 1 A g−1, according to CV and galvanostatic test, respectively; 292.5 F g−1 at a very high discharge current density of 20 A g−1. Furthermore, it exhibited an outstanding stability reflected by a high capacitive retention of 89.5% after a 2000-cycles test at a high current density of 10 A g−1. The excellent electrochemical performance is attributed to novel morphology Co3O4 HMs, which possesses large surface area, unique hierarchical porous structures and low equivalent series resistance.