Enhanced supercapacitor performance of BiOI nanoflowers/rGO nanocomposites with GO modified gel electrolyte

Abstract The pure bismuth oxyiodide (BiOI) nanoflower and BiOI/reduced graphene oxide (rGO) nano composites have been prepared via solvothermal route for supercapacitor application.Various mass ratios of BiOI with rGO were incorporated in this study. Additionally, the electrolyte gel was modified with graphene oxide (GO) to investigate the enhancement in supercapacitive charge storage properties. The structural and morphological properties of the pure BiOI nanoflower and BiOI/rGO hybrids were analysed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX), Transmission Electron microscopy (TEM), N 2 adsorption–desorption isotherms (BET) and X-ray photoelectron spectroscopy (XPS). The electrochemical performances of pure BiOI nanoflower and BiOI/rGO hybrids with different mass ratio were tested by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The optimal BiOI/rGO hybrid electrode delivered specific capacitance 235 F/g at scan rate 5 mV/s in PVA/H 2 SO 4 gel electrolyte with energy density 8.1 Wh/kg and power density 0.146 kW/kg, also with PVA/H 2 SO 4 + GO gel electrolyte 288 F/g at 5 mV/s scan rate with energy density 10 Wh/kg at power density 0.18 kW/kg. The BiOI/rGO hybrid electrode maintained capacitive retention of 79% and 71% after 10,000 successive CV cycles at scan rate 100 mV/s in PVA/H 2 SO 4 gel and PVA/H 2 SO 4 + GO gel electrolytes respectively.