03759ntm a2200289 a 4500 vtls000094030 KUKTEM 20251117113319.0 160321t2014 my a f 000 0 eng d THE0000142(Local) 201905131417 nazirah 201710041610 aishah 201603211656 shima 201603211436 shima UMP FIST .G66 2015 r Thesis Gomma Abdelgawad Mohammed Ali Preparation and characterization of manganese-based and carbon-based nanomaterials for supercapasitors application / Gomma Abdelgawad Mohammed Ali Kuantan, Pahang : UMP, 2015 xxiii, 121 p. : ill. (some col.) ; 30 cm. + 1 CD-ROM Faculty of Industrial Sciences & Technology Thesis (Doctor of Philosophy (Advanced Materilas) -- Universiti Malaysia Pahang – 2015 Bibliography : p. 109-121 In this study, electrochemical materials, namely MnO2, reduced graphene oxide (rGO), porous carbon nanoparticles (PCNs), and rGO/MnO2 nanocomposite, were prepared in diverse morphologies such as nanoflowers (MnO2), nanosheets (rGO), and nanoparticles (carbon). Different physical and chemical characterizations have been conducted to study the structural and morphological properties of the materials under study. Electrochemical properties of the above materials have been studied comprehensively using cyclic voltammetry (CV), galvanostatic charge–discharge (CDC) and electrochemical impedance spectroscopy (EIS) in order to evaluate their suitability as an electrode for supercapacitive energy storage. MnO2 nanoflowers was recovered from spent batteries by a combining leaching and electrowinning techniques. The recovered MnO2 nanoflowers exhibited high specific capacitance (Cs) (303 F g-1 at 5 mV s-1). Furthermore, MnO2 was electrodeposited by potentiostatic and galvanostatic conditions. Under similar electrodeposition conditions, MnO2 deposited by galvanostatic condition showed smaller particle size, less compact layered structure and wider band gap compared to potentiostatic deposition. The galvanostatic MnO2 rendered facile ions diffusion, low resistances and showed superior capacitive behavior. The rGO nanosheets were prepared by hydrazine reduction of graphene oxide and their electrochemical properties were studied. The rGO showed high Cs of 191 and 168 F g-1 at 5 mV s-1, in 5 M KOH and 1 M Na2SO4, respectively and high cycling stability > 96 % over 1000 cycles. In addition, PCNs with fine particles size of 35 nm were prepared from oil palm leaves using a catalyst free process. The Cs of PCNs is 245 and 213 F g-1 at 5 mV s-1 in 5 M KOH and 1 M Na2SO4, respectively. The PCNs showed high cycling stability of 95 %. Practical supercapacitors were developed using rGO and PCNs; the devices delivered energy densities ~18 and ~25 W h kg-1 at power densities 340 and 360 W kg-1, respectively, under wider operating voltage window of 2 V in neutral electrolyte. rGO/MnO2 nanocomposite has been prepared by simultaneous electrochemical conversion of GO and Mn3O4. The Cs of rGO/MnO2 is 457 F g-1 at 5 mV s-1, which are several folds higher compared to those for pure rGO and MnO2. Furthermore, rGO/MnO2 showed high stability of 95 % over 2000 CDC cycles. Therefore, the present study identifies electrochemical materials with improved energy storage capabilities. Faculty of Industrial Sciences & Technology Dissertations Universities and Colleges Dissertations Theses http://ecollib.ump.edu.my/3563/ Library access only 0 0 lcc 0 1 10000 10000 2019-09-04 0 FIST .G66 2015 r Thesis 0000107762 2019-09-04 00:00:00 1 2019-09-04 THESIS 0 0 lcc 0 1 10000 10000 2019-09-04 0 CD 9641 | FIST .G66 2015 r Thesis 0000107763 2019-09-04 00:00:00 1 2019-09-04 THESIS VIRTUA40 6571 6577 VTLSSORT0080*0200*0400*0900*1000*2450*2600*3000*5000*5020*5040*5200*6100*6500*6501*8560*9992