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008			201103t2 2 m a|||fram|| 000 0 eng d
020			_aTHE0008949(Local) _qhardback
040			_aUMP _beng _cUMP _erda
090			_aFIST .A47 2020 r Thesis
100	1		_aAbd Al-Rahman Thalji, Mohammad Rebhi, _eauthor.
245	1	0	_aTungsten oxide/reduced graphene oxide nanocomposite for supercapacitor applications / _cMohammad Rebhi Abd Al-Rahman Thalji
264		1	_aKuantan, Pahang : _bUMP, _c2020
264		4	_c© 2020
300			_axvii, 97 pages : _billustrations (some color) ; _c30 cm. + _e1 CD-ROM
336			_atext _2rdacontent
336			_atext _2rdacontent
337			_aunmediated _2rdamedia
337			_acomputer _2rdamedia
338			_avolume _2rdacarrier
338			_acomputer disc _2rdacarrier
347			_atext file _bPDF _2rda
500			_aFaculty of Industrial Sciences and Technology
502			_aThesis (Doctor of Philosophy) -- Universiti Malaysia Pahang – 2020
504			_aIncludes bibliographical references
520	3		_aAmong electrochemical energy storage devices, supercapacitor exhibits high power density and long-term stability. However, one main challenge that limits supercapacitors from their promising applications is their low energy density. Supercapacitors can be categorized into two types: electrical double-layer capacitance and pseudocapacitance. Recently, a new behavior of the charge storage mechanism, called intercalation pseudocapacitance, was considered. Unlike other mechanisms, the main benefit of this behavior is manifested by the intercalation of ions into the crystal tunnels of the active material without their crystalline phase change in short periods. In this work, the potential of Al3+ ions storage was investigated in the W18O49 nanostructured as electrode material for supercapacitor application. It was established that the Al3+ ions can be intercalated in the lattice crystal of W18O49 and participate in charge storage. The dominant charge storage mechanism was confirmed by looking at Trasatti's analysis and ex-situ x-ray diffraction (XRD). Perfect pseudocapacitive behavior was achieved with a specific capacitance of 350 F g-1 at 1 A g-1 and a long-term stability of 92% capacitance retention after 8000 cycles. Further investigation exhibited that introducing reduced graphene oxide (rGO) possesses a remarkable effect on the resulting capacitance in comparison to the pure W18O49 nanostructure. The as-prepared W18O49 NWs/rGO nanocomposite showed outstanding capacitance up to 560 F g-1 at 1 A g-1 and excellent stability capacitance retention of 94% after 12000 cycles. Electrochemical ex-situ XRD and ex-situ high-resolution transmission electron microscopy (HRTEM) measurements detected the changes in the interlayer spacing in the W18O49 crystal lattice along the b-axis during the charge-discharge processes, which concluded that mechanism of electrochemical storage in the W18O49 NWs/rGO nanocomposite is pseudocapacitive. Moreover, the asymmetrical supercapacitor (ASC), which based on W18O49 NWs/rGO as the negative electrode and rGO sheets as the positive electrode, was assembled. The ASC achieved a specific capacitance of 365.5 F g-1 at 1 A g-1, superior reversibility with capacitance retention of 96.7% after 12000 cycles and a high energy density of 28.5 Wh kg-1 with the power density of 751 W kg-1. The results show that the energy storage characteristics of W18O49 are improved significantly by the incorporation with rGO. Additionally, it can be served as a promising electrode material for the high-rate and high energy density supercapacitors. In conclusion, the results demonstrate that W18O49 NWs/rGO nanocomposite with further effective modification is a promising and practical candidate for the creation of fast and highly efficient devices for various applications.
610	2	0	_aFaculty of Industrial Sciences and Technology _xDissertations
650		0	_aUniversities and colleges _xDissertations
650		0	_aTheses
942			_2lcc _cRESTRICT