SWL-Mathematics and Natural Sciences

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Browsing SWL-Mathematics and Natural Sciences by Subject "Activated carbon monolith"

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    Effect of electrolyte concentration on performance of supercapacitor carbon electrode from fibers of oil palm empty fruit bunches
    (2015-09-07) Farma, Rakhmawati; Deraman, Mohamad; Talib; Awitdrus; Omar, Ramli; Ishak; Taer, Erman; Basri, Nur Hamizah; Dollah, Besek Nurdiana Mohd
    Fibers of oil palm empty fruit bunches were used to produce self-adhesive carbon grains (SACG). The SACG green monoliths were carbonized in N2 environment at 800°C to produce carbon monoliths (CM) and the CM was CO2 activated at 800°C for 4 hour to produce activated carbon monolith electrodes (ACM). The physical properties of the CMs and ACMs were investigated using X-ray diffraction, field emission scanning electron microscopy and nitrogen adsorption-desorption. ACMs were used as electrode to fabricate symmetry supercapacitor cells and the cells which used H2SO4 electrolyte at 0.5, 1.0 and 1.5 M were investigated using electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge-discharge standard techniques. In this paper we report the physical properties of the ACM electrodes and the effect of electrolyte concentration on the electrochemical properties the ACM electrodes
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    Physical and Electrochemical Properties of Supercapacitor Electrodes Derived from Carbon Nanotube and Biomass Carbon
    (2015-09-08) Farma, Rakhmawati; Deraman, Mohamad; Awitdrus; Talib; Omar, Ramli; Manjunatha; Ishak; Basri, Nur Hamizah; Dollah, Besek Nurdiana Mohd
    Green monoliths (GMs) were prepared from mixtures of KOH (5% by weight), carbon nanotubes (5%) and self-adhesive carbon grains (90%) from oil palm empty fruit bunch fibers. The GMs were carbonized up to 600, 700 and 800°C under an N2 gas environment, and activated by CO2 gas at 800°C for one hour to produce activated carbon monoliths (ACMs), designated as ACM6, ACM7 and ACM8, respectively. The characterization of the ACMs showed a notable effect of the carbonization temperature on the structure, microstructure, electrical conductivity and porosity of the ACMs. Consequently, three independent methods, galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy, used for the electrochemical characterization of supercapacitor cells fabricated using the ACMs as their electrodes, consistently found that the ACM7 and ACM8 cells have higher specific capacitance (77 Fg-1 and 85 Fg-1, respectively), specific energy (2.2 Wh kg-1 and 2.1 Wh kg-1, respectively) and specific power (156 W kg-1 and 161 W kg-1, respectively) compared to the ACM6 cell. These results suggest that carbonization should be performed at temperatures closer or equal to the activation temperature for the preparation of supercapacitor electrodes composed of biomass precursors.
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    Preparation of a Highly Porous Binderless Activated Carbon Monolith from Rubber Wood Sawdust by a Multi-Step Activation Process for Application in Supercapacitors
    (2015-09-09) Taer, Erman; Deraman, Mohamad; Talib; Awitdrus; Hashmi; Umar
    Binderless activated carbon monoliths (ACMs) with high porosity that were prepared from self-adhesive pre-carbonized rubber wood sawdust were studied as electrodes for supercapacitors, focusing on the influence of activation time on the physical and electrochemical properties of the ACMs. The ACMs were activated under a flow of CO2 gas at a rate of 0.5 liters per minute and at a temperature of 900 oC. Activation time varied from 1 to 6 hours and with a multi-step heating profile. The ACM was characterized physically (density, porosity, structure and surface morphology) and electrochemically (specific capacitance, equivalent series resistance, energy and power density). This study found that the combined effects from the length of activation time, binderless property and multi-step heating had the greatest influence on the physical and electrochemical properties of the ACM. The optimum ACM was activated for 5 hours and had a specific capacitance, equivalent series resistance, energy and power density of 138 F g-1, 0.49 Ohm, 2.63 Wh kg-1 and 291 W kg-1, respectively.