The morphology and phase conversion of MnO₂ in g-CN@MnO₂ composite with supercapacitor applications

This paper presents a method or preparing a composite with morphology and phase conversion appropriate for use in a supercapacitor. Manganese dioxide (MnO₂) nanoflakes composed of MnO₂ nanorods (α and γ phases) with protonated g-C₃N₄ (g-CN), were prepared via a hydrothermal method. As synthesized composite showed district morphology and phase conversion of MnO₂. The composite was thoroughly evaluated by field emission electron microscopy (FESEM), transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). Based on characterizations, morphology and phase conversion phenomenon of MnO₂ in g-CN/MnO₂ composite is suggested and discussed. The electrochemical performance of the composite was assessed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) and compared to the performance of bare g-CN and MnO₂ nanoflakes in alkaline electrolyte solution. The composite showed more specific capacitance (148.66 F/g) at 0.5 A/g than the pristine form of its components. An asymmetric supercapacitor (g-CN@MnO₂//PCNFs), assembled through a g-CN@MnO₂ composite and with porous carbon nanofibers (PCNFs), achieved an energy density of 1.6 Wh/Kg and a power density of 84 W/kg. This study suggests a new avenue for the development of MnO₂ based composites use as energy storage materials.