In situ synthesis of porous Co₃O₄ polyhedra/carbon nanotubes heterostructures for highly efficient supercapacitors

Currently, supercapacitors (SCs) have been applied widely in energy storage field. In this work, porous Co₃O₄ polyhedra (PCP)/carbon nanotubes (CNTs) heterostructures were designed by in situ implanting CNTs into ZIF-67 with a subsequent pyrolysis process and used for SCs. Their morphology, structure, and electrochemical performance were characterized by field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction spectroscopy, nitrogen adsorption-desorption, thermogravimetry analysis, cyclic voltammogram, galvanostatic charge-discharge, and electrochemical impedence spectra. The results show that the specific capacitance and cycling stability of the PCP electrodes are both increased after CNTs doping. As the temperature is increased to 350 °C, the obtained porous PCP/CNTs heterostructure exhibits the maximum specific capacitance (592 F g⁻¹ at 1 A g⁻¹) with long-term stability due to its high specific surface area and good electrical conductivity. The PCP/CNTs electrode should be a promising candidate for highly efficient electrode materials of SCs.