Template synthesis of 1D hierarchical hollow Co₃O₄ nanotubes as high performance supercapacitor materials

Highlights: • Hollow Co₃O₄ nanotubes was prepared by using activated carbon as a hard template. • Typical Co₃O₄ nanotubes possess the hierarchical mesoporous nanostructure. • High specific capacitance of 1006 F g⁻¹ is obtained at a current density of 1 A g⁻¹. • Excellent electrochemical stability of 91% after 1000 charge–discharge cycles. - Abstract: One-dimensional (1D) hierarchical hollow Co₃O₄ nanotubes have been controllably fabricated via a facile two-step strategy including template-hydrothermal reaction and calcination, in which cobalt sulfate heptahydrate, guanidine hydrochloride and activated carbon are used as cobalt precursors, precipitant and hard template, respectively. The resultants of Co₃O₄ are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) patterns and N₂ adsorption and desorption. The novel precipitant guanidine hydrochloride and hard template activated carbon contributed to the interesting morphology, and plus Kirkendall effect leading to producing hollow structure with hierarchical porous. The electrochemical properties of prepared different Co₃O₄ samples are evaluated and compared through cyclic voltammetry (CV), charge–discharge and electrochemical impedance spectroscopy (EIS) in 2.0 M KOH electrolytic solution. The results show that the 1D hierarchical hollow Co₃O₄ nanotubes exhibit a large specific capacitance of 1006 F g⁻¹ at 1 A g⁻¹, an outstanding cyclic stability with a capacitance retention of 91% after 1000 cycles of charge–discharge and a low resistance