Browsing by Author "Sirengo, Keith"

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Fish bladder-based activated carbon/Co3O4/TiO2 composite electrodes for supercapacitors
(Elsevier B.V., 2019-06-15) Sirengo, Keith; Jande, Yusufu; Kibona, Talam; Hilonga, Askwar; Muiva, Cosmas; King'ondu, Cecil
Cobalt oxide/titanium dioxide/activated carbon (Co3O4/TiO2/Ac) composite was synthesized using simple sol-gel method before annealing at 300 °C. Fish bladder derived porous carbon used for the composite was synthesized by pyrolysis followed by chemical activation. Both scanning electron microscopy (SEM) and X-ray diffraction displayed Co3O4 and TiO2 phases well embedded onto the carbon matrices. Cyclic voltammetry in 6 M KOH electrolyte demonstrated that the composite has an excellent specific capacity of 946 Fg-1 for Co3O4/TiO2/Ac as compared to Co3O4/Ac, TiO2/Ac, and Ac with specific capacitances of 845, 340, and 308 F g−1, respectively at 5 mVs−1. Impedance spectroscopy reveals that the composite has good capacitive behavior with a series resistance of 0.6 Ω. Besides, Co3O4/TiO2/Ac maintains 89.7% of the initial capacitance after 2000 cycles. This study shows that the synergistic effect of the metal oxides and the carbon in the composite can enhance capacitance for practical supercapacitor applications.
Fish bladder-based activated porous carbon/co3o4/tio2 composite electrodes for supercapacitors
(NM-AIST, 2020-02) Sirengo, Keith
Supercapacitors as energy storage devices depend on electrode materials, electrolyte and conductive additives. In relation to the above, this master’s dissertation specifically provides a scientific understanding and knowledge to the society on the use of fish bladder derived porous carbon for cobalt oxide/titanium dioxide/activated carbon (Co3O4/TiO2/Ac) composite as electrode materials for supercapacitor applications. Fish bladder was used as a carbon source for the composite after carbonization and chemical activation. Composites of Co3O4/TiO2/Ac, Co3O4/Ac, and TiO2/Ac were later synthesized using simple impregnation method followed by heat treatment and thereafter in-depth investigation on the active material was carried out through material characterization and electrochemical testing. X-ray diffraction and scanning electron microscopy (SEM) revealed that Co3O4 and TiO2 nano phases were well embedded over carbon matrices. Fourier transfer infra-red (FT-IR) measurements showed that the active material had oxygen containing functional groups. Cyclic voltammetry curves demonstrated that specific capacitance of the active material was 946 Fg -1 for Co3O4/TiO2/Ac as compared to Co3O4/Ac, TiO2/Ac, and Ac with specific capacitances of 845 F g-1 , 340 F g -1 , and 308 F g -1 , respectively at a scan rate of 5 mVs -1 . Impedance spectroscopy revealed good capacitive behavior with a series resistance of 0.5 Ω, 0.52 Ω, 0.6 Ω, and 1.1 Ω for Ac, Co3O4/Ac, Co3O4/TiO2/Ac, and TiO2/Ac, respectively. Excellent electrochemical performances observed for the Co3O4/TiO2/Ac electrode was a result of individual contribution of different characteristics of the binary metal oxides such as improved electric conductivity and wettability of the composites associated with porous carbon and TiO2.