STUDY OF THE EFFECT OF COAL RANK ON THE CHARACTERISTICS AND ELECTROCHEMICAL PERFORMANCE OF COAL-DERIVED REDUCED GRAPHENE OXIDE

• Main Author: Rizky Ardiansyah, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86324
• Institution: Institut Teknologi Bandung

The role of new renewable energy (NRE) is increasingly vital to reduce global emissions, but most of its supply availability is affected by time and weather. Therefore, energy storage media, such as supercapacitors, need to be used to ensure EBT can supply continuously into the national electricity system. One of the components of supercapacitors is graphene, which is a carbon material with superior electrical and mechanical properties. However, graphite, which is the precursor material for graphene, is not widely available in Indonesia, so an alternative material source is needed to produce graphene locally. On the other hand, Indonesia has sizable coal reserves. Coal has the potential to be an alternative graphene precursor via reduced graphene oxide (RGO) due to its high carbon content. Therefore, this research focuses on studying the characteristics of RGO produced from two types of coal with different ranks. The experiments were conducted using sub-bituminous (RCS) and lignite (RCL) coal pulverized to -200 mesh size. Then, the coal was leached gradually with 1 M HF and 0.5 M HNO3, followed by HNH carbonization at 800°C with a heating rate of 5°C/min and a holding time of 2 hours, to produce carbonized clean coal (CCL, CCS). The CCL and CCS samples were then synthesized into graphene oxide (GO) using the modified Hummers method (GOL, GOS). Then GO was reduced to obtain RGO using ascorbic acid by rapid heating using microwave for 3 minutes at 1,000 Watts with pH variations of 7, 9 and 11 (rGOL 7, rGOL 9 rGOL 11, rGOS 7, rGOS 9, rGOS 11). Then, GO and RGO samples were fabricated into electrodes and carried out cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) tests with a three-electrode system instrument to determine the specific capacitance of the electrode. The RCL, RCS, CCL, CCS, GO, RGO samples were characterized using fourier transform infrared spectroscopy (FTIR), scanning electron microscope - energy dispersive spectroscopy (SEM-EDS) and x-ray diffraction (XRD). The results showed that the leaching and carbonization processes effectively reduced the ash content of RCS and RCL. The GOL sample underwent higher oxidation than GOS, with the oxygen content increasing by 5331%, to 14.12 wt% with d(002) GOL of 0.397 nm, and specific capacitance of 156 F/g at a current density of 0.5 A/g. Meanwhile, GOS has an oxygen content of 9.3 wt% or only increased by 621%, with a d(002) of 0.394 nm and a specific capacitance of 136.73 F/g at a current density of 0.5 A/g. The best reduction process was shown by rGOS9 and rGOL 9 with specific capacitance of 207.98 F/g and 204.58 F/g at current density of 0.5 A/g.