Electrochemical performance of corncob-derived activated carbon-graphene oxide and TiO2 ternary composite electrode for supercapacitor applications

Abstract

Composite electrode materials have been extensively studied and utilized in the fabrication of supercapacitors owing to their superior electrochemical properties. These materials have been noted to utilize both electric double layer and pseudocapacitive effect to store energy in supercapacitors. In this work, activated carbon (AC) was synthesized from corncob using a hydrothermal technique. Graphene oxide (GO) was also synthesized from corncob using the improved Tour's method. The as-synthesized AC was used in forming electrodes by separately compositing it with titanium dioxide (TiO2) and GO-TiO2 respectively. The prepared samples were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, and the Brunauer – Emmett – Teller (BET) analysis. Electrochemical performance was carried out using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD) analysis. The SEM micrographs showed high porosity for all the fabricated electrodes. XRD analysis showed the presence of (002) plane responsible for electrical conductivity in the composite electrode. The Raman and FTIR spectra indicated successful synthesis of GO. The as-synthesized AC showed a specific surface area of 212.55 m2g−1 with a specific pore volume of 0.11 cm3g−1. The addition of TiO2 to the AC recorded a 62.09 % enhancement in the specific surface area. The result revealed that forming the ternary composite (AC-TiO2-GO) had a pronounced effect on the surface morphology and pore structure of the corncob-derived AC. The specific capacitance at 10 mV/s of the formulated composite electrodes increases in the order AC (69.790 F/g), AC-TiO2 (159.281 F/g), and AC-TiO2-GO (219.375 F/g). The equivalent series resistance (ESR) was observed to show decreasing values in the order AC (5.34 Ω), AC-TiO2 (2.67 Ω), and AC-TiO2-GO (1.87 Ω). The electrochemical performance of the formulated electrodes indicates that AC-TiO2-GO could be a promising candidate material for use in energy storage devices where relatively high-performance is required.