Facile synthesis of hollow Co3O4 boxes for high capacity supercapacitor

One-dimensional (1D) cobalt acetate hydroxide (Co5(OH)2(CH3COO)8·2H2O) prisms has been obtained through a low temperature re-crystallization process in the dissolvant of ethanol and then transferred to cobalt oxide by calcining in the air. Cobalt oxide keeps the outside configuration of the 1D cobalt acetate hydroxide but turns to be boxes with hollow structure inside through the Kirkendall effect. The precursor prisms and polycrystalline boxes both have length of about 3 μm, width of 300 nm and height of 300 nm characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical measurement results show that the hollow Co3O4 structures exhibit wonderful capacitive properties with high capacitance and good cyclicity.

► Cobalt acetate hydroxide prisms were obtained by a low temperature re-crystallization process.
► Hollow Co3O4 boxes were obtained by calcining cobalt acetate hydroxide prisms in air.
► Hollow Co3O4 structures exhibit wonderful capacitive properties.