A High Performance Supercapacitor Based on Graphene/Polypyrrole/Cu₂O–Cu(OH)₂ Ternary Nanocomposite Coated on Nickel Foam

Abstract

A simple and low-cost electrochemical deposition method is used to prepare reduced graphene oxide/polypyrrole/Cu2O–Cu(OH)2 (RGO/PPy/Cu2O–Cu(OH)2) ternary nanocomposites as the electrode material for supercapacitor application. First, graphene oxide–polypyrrole (GO/PPy) nanocomposite is electrochemically synthesized on Ni foam by electro-oxidation of pyrrole monomer in an aqueous solution containing GO and Tiron. Subsequently, the GO/PPy film is converted to the corresponding reduced form (RGO/PPy) by an effective and eco-friendly electrochemical reduction method. Then, a thin layer of Cu2O–Cu(OH)2 is formed on RGO/PPy film by chronoamperometry. The RGO/PPy/Cu2O–Cu(OH)2 nanocomposite is characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier transform infrared spectra (FT-IR). SEM images show that Cu2O–Cu(OH)2 nanoparticles are dispersed on the surface of RGO/PPy film with an average particle size of 50–70 nm. The electrochemical performance of the as-prepared electrode is evaluated by various electrochemical methods using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) in 0.5 M Na2SO4 solution. In the three-electrode system, RGO/PPy/Cu2O–Cu(OH)2 exhibits an excellent gravimetric specific capacitance of 997 F g–1 at a current density of 10 A g–1, which is far better than GO/PPy (500 F g–1), RGO/PPy (685.5 F g–1), and GO/PPy/Cu2O–Cu(OH)2 (750F g–1). The utilization of the electrical double layer capacitance (EDLC) of graphene together with the pseudocapacitive behavior of PPy and Cu2O–Cu(OH)2 leads to a maximum energy density of 20 Wh kg–1 at power density of 8000 W kg–1 and a maximum power density of 19 998.5 W kg–1 at an energy density of 5.8 Wh kg–1 for symmetric RGO/PPy/Cu2O–Cu(OH)2 supercapacitor. Furthermore, RGO/PPy/Cu2O–Cu(OH)2 nanocomposite maintains about 90% of the initial capacitance value after 2000 cycles.