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Title: Conversion of spent coffee beans into reduced graphene oxide by Hummer's method as electrode for vanadium redox applications
Authors: Eng, Xue Er
Keywords: Engineering::Environmental engineering
Issue Date: 2020
Publisher: Nanyang Technological University
Abstract: The vanadium redox flow battery (VRB) is a renowned electrochemical energy storage device that has been used widely due to its promising storage capability. However, finite and non-renewable based pristine graphite such as TF6 graphite plates, are commonly used for commercial applications in VRB. Thus, this project focuses on the feasibility of converting spent coffee beans to an electrode material in replacement of commercial graphite plates. The spent coffee beans are first converted to biochar by pyrolysis and then chemically activated using Hummer’s method. Afterwards, a reduction by hydrohalic acid is performed to synthesize reduced graphene oxide (rGO). The material properties of the samples obtained are characterised by CHNS analysis, Thermogravimetry analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, Brunauer-Emmette-Teller, Transmission electron microscopy and Field emission scanning electron microscope while the electrochemical characteristic and performance of these samples are carried out using Electrochemical impedance spectroscopy, Cyclic voltammetry and Galvanostatic charge-discharge test. The overall results show that the energy efficiency of these samples ranges from 84% to 90% and the efficiency does not deteriorate significantly after a total of 65 cycles. Among these rGO synthesized sample, the 850°C rGO samples are identified as potential low-cost replacement to that of TF6 graphite as their energy efficiency performance are quite comparable within ~2% difference which may be attributed to increase ohmic resistance due to the slight increase in electrode thickness.
Schools: School of Civil and Environmental Engineering 
Research Centres: Environmental Engineering Research Centre 
Nanyang Environment and Water Research Institute 
Fulltext Permission: restricted
Fulltext Availability: With Fulltext
Appears in Collections:CEE Student Reports (FYP/IA/PA/PI)

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