Fabrication of an asymmetric supercapacitor based on reduced graphene oxide/polyindole/γ−Al₂O₃ ternary nanocomposite with high-performance capacitive behavior

This report describes the design and fabrication of reduced graphene oxide/polyindole/γ-Al₂O₃ (RGO/PIn/γ-Al₂O₃) ternary nanocomposite electrode materials for asymmetric supercapacitors. The nanocomposite was prepared by chronoamperometry on a gold electrode. Polyindole (PIn) and RGO/PIn were prepared electrochemically and their performances were compared with RGO/PIn/γ-Al₂O₃. The structures and morphologies of samples were characterized by FESEM, EDX, XRD and FT-IR. To get electrochemical charasteristics of the RGO/PIn/γ-Al₂O₃ electrode in a HClO₄ solution electrolyte Cyclic voltammetry (CV) technique, electrochemical impedance spectroscopy (EIS) and galvanostatic charging and discharging were carried out. The results show that RGO/PIn/γ-Al₂O₃ performed well with a specific capacitance of 308 F/g in comparison with PIn (93 F/g) and RGO/PIn (214 F/g). RGO as the negative and RGO/PIn/γ-Al₂O₃ as the positive electrode were used to fabricate an asymmetric supercapacitor. The asymmetric RGO/1.0 M HClO₄/RGO/PIn/γ-Al₂O₃ supercapacitor can be cycled in a high voltage range of 0.0–1.4 V that displayed a high energy density of 10 Wh/kg at a 3880 W/kg power density and a specific capacitance of 38.46 F/g. Furthermore, after 5000 cycles, 83% of the RGO/PIn/γ-Al₂O₃ initial capacitance was maintained.