Activated Carbon and Graphene Oxide for Supercapacitors and Batteries Application

Abstract

Carbon-based materials are widely used for energy storage systems because of their unique properties, low cost, and availability. These include Graphite, graphene, activated carbon, graphene oxide, carbon nanotube, carbon forms, carbon aerogel etcetera. Graphite is a mineral mined from different parts of the world which includes Africa. It can be used or converted into different carbon materials such as exfoliated graphite, graphene, Graphene Oxide (GO), graphene nanoplatelets, carbon nanotubes, onions among others by chemical or mechanical methods. In this study, the locally mined graphite flakes were converted to GO using chemical methods known as Hummer’s oxidation method (HM). This method was also compared with other modified Hummer’s methods by altering the conditions and the materials used. The synthesized GO materials were characterized by different techniques such as UV-Vis spectroscopy, FTIR, SEM EDX, XRD, and electrochemical analysis. The morphology, functional groups, different bonds, elemental percentage, crystallographic structure, and energy storage applicability were examined. The techniques confirmed the formation of functional groups like C-O, C=O, and the C/O ratio in the materials. The electrochemical characterization performance of materials produced the highest specific capacitance of 211.2 F/g with a current density of 0.5 A/g and the specific energy of 7.33 Wh/kg. In this work, African Maize Cobs (AMC) was used as a rich biomass precursor in synthesizing carbon material through a chemical activation process for application in electrochemical energy storage devices. The carbonization and activation were carried out with concentrated sulphuric acid and potassium hydroxide. The activation was carried out using three different temperatures of 600, 700, and 800 oC. The activated carbon exhibited excellent microporous and mesoporous structures with a specific surface area that ranges between 30 - 254 m2g-1 as measured by BET analysis. The morphology and structure of the produced materials are analyzed through Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Boehm titration, X-ray Photoelectron Spectroscopy (XPS), and Raman Spectroscopy. X-ray photoelectron spectroscopy indicates that a considerable amount of oxygen is present in the materials. The functional groups in the activated carbon enhanced the electrochemical performance and improved the double-layer capacitance of the material. The acid-activated material at 700°C exhibited excellent capacitance of 456 F g-1 at a specific current of 0.25 A g-1 in 6 M KOH electrolyte and show excellent stability after 10,000 cycles. The alkaline activated produced materials delivered a specific capacitance of 358.7 F/g with an energy density of 12.45 Wh/kg and a corresponding power density of 250 W/kg at 0.5 A/g. In addition to being low cost, the produced materials show excellent stability and electrochemical properties, thus suitable, as is a potential material for supercapacitor application. The hydrothermal method is used in heteroatomic metal oxide-graphene doping for improvement of the material properties. The NaFe2O3-GO composite was produced by batch hydrothermal method. The synthesised composite was tested for battery application. The material was characterized by FESEM/EDX, XRD, and electrochemical testing of the material which resulted in the performance of the discharge capacity approximated to be 720 mAh/g.