TY  - MANSCPT
AU  - Abd Al-Rahman Thalji,Mohammad Rebhi
TI  - Tungsten oxide/reduced graphene oxide nanocomposite for supercapacitor applications
SN  - THE0008949(Local)
PY  - 2020///
CY  - Kuantan, Pahang
PB  - UMP
KW  - Faculty of Industrial Sciences and Technology
KW  - Dissertations
KW  - Universities and colleges
KW  - Theses
N1  - Faculty of Industrial Sciences and Technology; Thesis (Doctor of Philosophy) -- Universiti Malaysia Pahang – 2020; Includes bibliographical references
N2  - Among 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
ER  -