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Effect of sulphuric acid concentration of hummers’ method in reduced graphene oxide synthesis and its electrochemical study / Lim Wan Sin

By:

Lim, Wan Sin [author.]

Material type: Text

text
text

Media type:

unmediated
computer

Carrier type:

volume
computer disc

ISBN:

THE0008932(Local)

Subject(s):

Dissertation note: Thesis (Master of Science) -- Universiti Malaysia Pahang – 2019 Abstract: Sulphuric acid is an intercalation agent that commonly utilized during the chemical oxidation process in the modified Hummers’ method. The presence of sulphuric acid serves as intercalated molecules that significant to enhance the reactive of graphite surface for further oxidation. The aims of the study are to prepare graphene oxide (GO) through modification of the Hummers’ method by controlling the sulphuric acid concentration during the first step of oxidation and determine the electrochemical performance of the reduced graphene oxide (rGO). Ultraviolet-visible spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Field Emission Scanning Electron Microscope (FESEM) were used to characterize the composition and morphology of GO samples. After reduction by hydrazine monohydrate, rGO was characterized using XPS and Brunauer-Emmett-Teller (BET) surface area analysis. Then the electrochemical studies of rGO have been evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) using the three-electrode system. Based on XPS results, it was found that in the case of 98 % (GO98) and 90 % (GO90), the edge oxidized GO was dominant. After reduced the edge oxidized GO (rGO98 and rGO90) reached the specific capacitance 160 and 185 F g-1 at current density 0.5 A g-1. With the further reduction of the sulphuric acid concentration to 80 % (GO80) and 70 % (GO70), basal oxidized GO was obtained. However, the specific capacitance reduced to 146 and 120 F g-1. The EIS revealed that rGO90 has higher electron mobility and lower resistance than rGO98, rGO80 and rGO70. The stability of rGO90 after 10000 cycles showed 94 % capacitance retention which is higher than rGO98, rGO80, and rGO70 with capacitance retention 86, 85, and 80 %, respectively. Hence, it demonstrated that sulphuric acid concentration significantly influences on oxygen oxidized location either edge or basal plane during GO formation and also its electrochemical performance after reduction.

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Holdings ( 2 )
Title notes ( 4 )

Holdings
Item type	Current library	Collection	Call number	Copy number	Status	Date due	Barcode
Thesis	UMPLIB GAMBANG	Reference	FSTI .L56 2019 r Thesis (Browse shelf(Opens below))	1	Not for loan		T000000970
Thesis	UMPLIB GAMBANG	Reference	CD12712 (Browse shelf(Opens below))	1	Not for loan		T000000971

Faculty of Industrial Sciences and Technology

Thesis (Master of Science) -- Universiti Malaysia Pahang – 2019

Includes bibliographical references

Sulphuric acid is an intercalation agent that commonly utilized during the chemical oxidation process in the modified Hummers’ method. The presence of sulphuric acid serves as intercalated molecules that significant to enhance the reactive of graphite surface for further oxidation. The aims of the study are to prepare graphene oxide (GO) through modification of the Hummers’ method by controlling the sulphuric acid concentration during the first step of oxidation and determine the electrochemical performance of the reduced graphene oxide (rGO). Ultraviolet-visible spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Field Emission Scanning Electron Microscope (FESEM) were used to characterize the composition and morphology of GO samples. After reduction by hydrazine monohydrate, rGO was characterized using XPS and Brunauer-Emmett-Teller (BET) surface area analysis. Then the electrochemical studies of rGO have been evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) using the three-electrode system. Based on XPS results, it was found that in the case of 98 % (GO98) and 90 % (GO90), the edge oxidized GO was dominant. After reduced the edge oxidized GO (rGO98 and rGO90) reached the specific capacitance 160 and 185 F g-1 at current density 0.5 A g-1. With the further reduction of the sulphuric acid concentration to 80 % (GO80) and 70 % (GO70), basal oxidized GO was obtained. However, the specific capacitance reduced to 146 and 120 F g-1. The EIS revealed that rGO90 has higher electron mobility and lower resistance than rGO98, rGO80 and rGO70. The stability of rGO90 after 10000 cycles showed 94 % capacitance retention which is higher than rGO98, rGO80, and rGO70 with capacitance retention 86, 85, and 80 %, respectively. Hence, it demonstrated that sulphuric acid concentration significantly influences on oxygen oxidized location either edge or basal plane during GO formation and also its electrochemical performance after reduction.