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 115m(2) 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. (C) 2013 Elsevier B.V. All rights reserved.