Browsing by Author "Kanwal"

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    Impedance spectroscopic analysis of composite electrode from activated carbon/conductive materials/ruthenium oxide for supercapacitor applications
    (2015-09-07) Taer, Erman; Deraman, Mohamad; Talib; Awitdrus; Farma, Rakhmawati; Ishak; Omar, Ramli; Dollah, Besek Nurdiana Mohd; Basri, Nur Hamizah; Othman; Kanwal
    Activated carbon powders (ACP) were produced from the KOH treated pre-carbonized rubber wood sawdust. Different conductive materials (graphite, carbon black and carbon nanotubes (CNTs)) were added with a binder (polivinylidene fluoride (PVDF)) into ACP to improve the supercapacitive performance of the activated carbon (AC) electrodes. Symmetric supercapacitor cells, fabricated using these AC electrodes and 1 molar H2SO4 electrolyte, were analyzed using a standard electrochemical impedance spectroscopy technique. The addition of graphite, carbon black and CNTs was found effective in reducing the cell resistance from 165 to 68, 23 and 49 Ohm respectively, and increasing the specific capacitance of the AC electrodes from 3 to 7, 17, 32 F g-1 respectively. Since the addition of CNTs can produce the highest specific capacitance, CNTs were chosen as a conductive material to produce AC composite electrodes that were added with 2.5 %, 5 % and 10 % (by weight) electro-active material namely ruthenium oxide; PVDF binder and CNTs contents were kept at 5 % by weight in each AC composite produced. The highest specific capacitance of the cells obtained in this study was 86 F g-1, i.e. for the cell with the resistance of 15 Ohm and composite electrode consists of 5 % ruthenium oxide.
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    Supercapacitors using binderless composite monolith electrodes from carbon nanotubes and pre-carbonized biomass residues
    (2015-09-10) Basri, Nur Hamizah; Deraman, Mohamad; Kanwal; Talib; Manjunatha; Aziz; Farma, Rakhmawati
    Binderless composite monolith (BCM) electrodes prepared from carbon nanotubes (CNTs) and self-adhesive carbon grains (SACGs) were used in a symmetrical supercapacitor. The SACGs were prepared from fibers of oil palm empty fruit bunches (EFBs) from oil palm tree (Elaeis guineensis), Heliotropium dasycarpum (H. dasycarpum) and Guaiacum officinale (G. officinale). For each biomass, the BCMs were prepared by the carbonization and activation of green monoliths (GMs) containing SACGs treated with KOH and a mixture of SACGs and CNTs treated with KOH. Thermal decomposition behavior of all SACGs was found to be slightly different because of the difference in their compositions. In addition, BCMs from H. dasycarpum and G. officinale were found to have SiO2. The BET surface areas were 1656, 1031 and 532 m2 g 1 for the BCMs from EFB, H. dasycarpum and G. officinale, respectively, and these values decreased by 40, 50 and 31% upon CNTs addition. Consequently, the specific capacitance decreased from w124 to w104 and w49 F g 1 to w111, w87 and w31 F g 1, respectively. However, addition of CNTs reduced the equivalent series resistance (ESR) by a factor of 83.9 (EFB), 90.6 (H. dasycarpum) and 38.8 (G. officinale) %. It was also found that CNTs addition contributed to improving the decay of Csp with increasing scan rate if the electrode surface area was sufficiently high.