The effect of cationic CTAB surfactants on the performance of graphene electrode for supercapacitor

Abstract

Graphene is a two-dimensional sp2 bonded carbon nanostructure packed in a honeycomb crystal lattice. Graphene has a high theoretical surface area and electrical conductivity that is suitable for the electrode of supercapacitors. There are many methods to produce graphene, such as mechanical exfoliation using scotch tape, reduction of graphene oxide, and chemical vapor deposition. An alternative and simple method to produce graphene is through pyrolysis process. The previous study shows that the production of graphene from biomass via two-stage pyrolysis process results in an increase of the surface area; however, its capacitance is still low to be applied as the electrode for supercapacitor. This study aims to modification of graphene surface using cetyltrimethylammonium bromide (CTAB) as the surfactant. The graphene was produced from palm kernel shell via two-stage pyrolysis method (the first stage was at 350°C followed by the second stage at 900°C) using FeCl3 as catalyst and ZnCl2 as activating agent, resulting in 16% yield. Graphene was analyzed using Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Raman scattering, X-ray Diffraction (XRD), and Fourier Transform Infrared (FTIR). These analyses show that the two-stage pyrolysis produces multi-layered graphene. The surface properties were analyzed by nitrogen adsorption-desorption measurements, which show some mesoporous graphene product with a surface area of 351.27 m2/g. The result exhibited more hydrophilic graphene than the unmodified one, but according to the Cyclic Voltammetry (CV) analysis, the specific capacitance of modified graphene (11.91 Fg-1) is lower than unmodified graphene (43.87 Fg-1).