Browsing by Author "Omar, Ramli"

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    Binderless Composite Electrode Monolith from Carbon Nanotube and Biomass Carbon Activated by H2SO4 and CO2 Gas for Supercapacitor
    (2015-09-07) Deraman, Mohamad; Ishak; Farma, Rakhmawati; Awitdrus; Taer, Erman; Talib; Omar, Ramli
    Binderless composite electrodes in the monolithic form prepared from carbon nanotubes (CNTs) and self‐adhesive carbon grains (SACG) from fibers of oil palm empty fruit bunch were studied as an electrode in a supercapacitor. The green monoliths (GMs) were prepared from three different types of precursors, SACG, SACG treated with 0.4 Molar H2SO4 and mixture of SACG and 5% CNTs (by weight) treated with 0.4 Molar H2SO4, respectively. These GMs were carbonized at 600 °C in N2 gas environment and activated by CO2 gas at 800 °C for 1 hour to produce activated carbon monoliths (ACMs). The properties of the ACMs (density, porosity, microstructure, structure and electrical conductivity) were found affected by CNTs addition and acid treatment. The acid treatment did not improve the electrochemical behavior of the ACMs used as electrodes (specific capacitance, specific energy and specific power of the supercapacitor) in the supercapacitor cells but CNTs addition improves the equivalent series resistance of the cell.
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    Binderless Composite Electrode Monolith from Carbon Nanotube and Biomass Carbon Activated by KOH and CO2 Gas for Supercapacitor
    (2015-09-07) Farma, Rakhmawati; Deraman, Mohamad; Omar, Ramli; Awitdrus; Ishak; Taer, Erman; Talib
    This paper presents a method to improve the performance of supercapacitors fabricated using binderless composite electrode monolith (BCMs) from self‐adhesive carbon grains (SACG) of fibers from oil palm empty fruit bunches. The BCMs were prepared from green monoliths (GMs) contain SACG, SACG treated with KOH (5 % by weight) and SACG mixed with carbon nanotubes (CNTs) (5% by weight) and KOH (5 % by weight), respectively. These GMs were carbonized at 800 °C under N2 environment and activated by CO2 gas at 800 °C for 1 hour. It was found that addition of KOH and CNTs produced BCMs with higher specific capacitance and smaller internal resistance, respectively. It was also found that supercapacitor cells using these BCMs as electrodes exhibited a better specific energy and specific power. The physical properties of BCMs (density, electrical conductivity, porosity, interlayer spacing, crystallite dimension and microstructure) were affected by the addition of KOH and CNTs.
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    Effect of carbonization temperature on the physical and electrochemical properties of supercapacitor electrode from fibers of oil palm empty fruit bunches
    (2015-09-07) Ishak; Deraman, Mohamad; Talib; Basri, Nur Hamizah; Awitdrus; Farma, Rakhmawati; Taer, Erman; Omar, Ramli; Dollah, Besek Nurdiana Mohd
    Self-adhesive carbon grains (SACG) was prepared from fibers of oil palm empty fruit bunches. The SACG green monoliths were carbonized in N2 environment at 400, 500, 600 and 700°C to produce carbon monoliths labeled as CM1, CM2, CM3 and CM4 respectively. The CMs were activated in CO2 surrounding at 800°C for 1 hour to produce activated carbon monolith electrodes (ACM1, ACM2, ACM3 and ACM4). The physical properties of the CMs and ACMs were investigated using X-ray diffraction, field emission scanning electron microscopy (FESEM) and N2 adsorption-desorption isotherm techniques. ACMs were used as electrode to fabricate symmetry supercapacitor cells and the cells’ performances were investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) standard techniques. In this paper we report the physical and electrochemical properties of the ACM electrodes by analyzing the influence of the carbonization temperature on these properties
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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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    Effects of Activation Time on the Performance of Supercapacitor Binderless Activated Carbon Electrodes Derived from Fibers of Oil Palm Empty Fruit Bunches
    (2015-09-07) Ishak; Deraman, Mohamad; Dollah, Besek Nurdiana Mohd; Othman; Omar, Ramli; Basri, Nur Hamizah; Nor, Najah Syahirah Mohd; Taer, Erman; Awitdrus; Farma, Rakhmawati; Aziz
    Green monoliths (GMs) with different composition, labelled as GM1, GM2 and GM3, were prepared from self-adhesive carbon grains (SACG) produced from fibers of oil palm empty fruit bunches, SACG treated with 0.4 M H2SO4 and mixtures of SACG and carbon nanotubes (5 wt.%) treated with 0.4 M H2SO4, respectively. Each GMs was carbonized and then activated with holding time of 1 h and 2 h, respectively, to produce their respective activated carbon monoliths (ACMs). These ACMs were used as electrodes to fabricate supercapacitor cells using H2SO4 electrolytes, Teflon separator and stainless steel 316L current collector. The porosity of the ACMs, examined by nitrogen adsorption-desorption isotherm method were found affected after prolonging the activation time. From the electrochemical characterization of the ACMs electrodes using galvanic charge-discharge methods, it was found that supercapacitor cells fabricated using the ACMs produced by longer activation time (2 h) showed better performance, which had higher specific capacitance (113 F/g), specific power (159 W/kg) and specific energy (3.35 W h/kg), compared to the cells using ACMs produced by shorter activation time (1 h).
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    Electrical Conductivity Of Carbon Pellets Prepared From Mixtures Of Pyropolymers From Oil Palm Bunches and Petroleum Green Coke
    (2015-09-07) Deraman, Mohamad; Awitdrus; Talib; Omar, Ramli; Jumali; Ishak; Saad; Taer, Erman; Saman; Farma, Rakhmawati; Yunus
    reen pellets (GPs), prepared at different compression pressures (cs = 6, 7.5 and 12 metric tonne) from mixtures containing self‐adhesive carbon grains (sacg) from the oil palm empty fruit bunch (EFB) and different percentages (pr = 0 to 90%) of a non self‐adhesive powder of petroleum green coke (ppgc), were carbonized (800° C) and activated with CO2 to produce carbon pellets (CPs). The measured electrical conductivity (σ) of the CP for all cs showed a curve having a minimum value at pr around 50%, indicating that the conducting phase displays a nonlinear σ‐ pr relationship. A significant increase in the σ due to CO2 activation was observed. For a sufficienctly high cs, an existence of a pr range in which the σ varies linearly with the density was also observed. These results provide some new information for modifying the electrical conductivity of carbon derived from the sacg from EFB or other types of biomass.
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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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    Influence of gamma irradiation exposure on the performance of supercapacitor electrodes made from oil palm empty fruit bunches
    (2015-08-18) Nor, Najah Syahirah Mohd; Deraman, Mohamad; Omar, Ramli; Awitdrus; Farma, Rakhmawati; Basri, Nur Hamizah; Dolah, Besek Nurdiana Mohd; Mamat, Nurul Fatin; Yatim, Baharudin; Daud, Mohd Norizam Md
    Carbon-monolith electrodes for supercapacitors were prepared from GMs (green monoliths) made from pre-carbonized fibers of oil palm EFB (empty fruit bunches) and GMs of pre-carbonized EFB fibers exposed to gamma radiation at 5 kGy, 15 kGy, and 20 kGy. GMs and irradiated GMs were carbonized and activated to prepare ACM (activated-carbon-monolith) electrodes. The gamma radiation affected the pore structure of the ACM electrodes and the electrochemical performance of the supercapacitors; irradiation doses of 0 kGy, 5 kGy, 15 kGy and 20 kGy produced specific capacitances of 121 F g 1, 196 F g 1, 11 F g 1, and 12 F g 1, respectively. The irradiation dose of 5 kGy appears to be optimum and produces a specific power and specific energy of 236 W kg 1 and 5.45 W h kg 1, respectively, representing 34% and 60% increases over ACM electrodes prepared from non-irradiated GMs.
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    Microcrystallite Dimension and Total Active Surface Area of Carbon Electrode from Mixtures of Pre-Carbonized Oil Palm Empty Fruit Bunches and Green Petroleum Cokes
    (2015-09-07) Awitdrus; Deraman, Mohamad; Talib; Omar, Ramli; Jumali, Mohd Hafizuddin; Taer, Erman; Saman, Mansor mohd
    Carbon pellets (CP) were prepared from the green pellets (GP) containing mixtures of pre-carbonized oil palm empty fruit bunches (SACG) and Green Petroleum Cokes (GPC), with the weight percentages (x) of SACG in the samples at 10%, 30%, 50%, 70% and 90%. Carbonization process to produce the CP was conducted up to 900oC using a multi steps heating profile. The interlayer spacing (d200 and d100), stack height (Lc), stack width (La,) and effective dimension L of the turbostratic crystallites (microsrystallite) in the CPs were estimated from X-ray diffraction data; d200, d100, La, L increased and Lc decreased with increasing weight percentage of SACG. The total surface area of active material of the CP (Atot) with thickness, t, estimated from Lc was found to follow the equation, Atot = [4.8086 – 0.0083x]1010 t, indicating a significant influence of the SACG content in the mixture of the green body.
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    Nanoporous separators for supercapacitor using activated carbon monolith electrode from oil palm empty fruit bunches
    (2015-09-06) Nor, Najah Syahirah Mohd; Deraman, Mohamad; Omar, Ramli; Taer, Erman; Awitdrus; Farma, Rakhmawati; Basri, Nur Hamizah
    Activated porous carbon electrode prepared from fibres of oil palm empty fruit bunches was used for preparing the carbon based supercapacitor cells. The symmetrical supercapacitor cells were fabricated using carbon electrodes, stainless steel current collector, H2SO4 electrolyte, and three types of nanoporous separators. Cells A, B and C were fabricated using polypropylene, eggshell membrane, and filter paper, respectively. Electrochemical characterizations data from Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, and Galvanic Charge Discharge techniques showed that specific capacitance, specific power and specific energy for cell A were 122 F g-1, 177 W kg-1, 3.42 Wh kg-1, cell B; 125 F g- 1, 179 W kg-1, and 3.64 Wh kg-1, and cell C; 180 F g-1, 178 W kg-1, 4.27 Wh kg-1. All the micrographs from Field Emission Scanning Electron Microscope showed that the different in nanoporous structure of the separators lead to a significant different in influencing the values of specific capacitance, power and energy of supercapacitors, which is associated with the mobility of ion into the pore network. These results indicated that the filter paper was superior than the eggshell membrane and polypropylene nanoporous separators. However, we found that in terms of acidic resistance, polypropylene was the best nanoporous separator for acidic medium.
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    Physical and electrochemical properties of supercapacitor composite electrodes prepared from biomass carbon and carbon from green petroleum coke
    (2015-09-09) Awitdrus; Deraman, Mohamad; Talib; Farma, Rakhmawati; Omar, Ramli; Ishak; Taer, Erman; Dollah, Besek Nurdiana Mohd; Basri, Nur Hamizah; Nor, Najah Syahirah Mohd
    The green monoliths (GMs) were prepared from the mixtures of pre-carbonized fibers of oil palm empty fruit bunches (or self-adhesive carbon grains (SACG)) and green petroleum coke (GPC) with the mixing ratio of 0, 10, 30, 50 and 70 % GPC, respectively. The GMs were carbonized in N2 environment at 800oC to produce carbon monoliths (CM00, CM10, CM30, CM50 and CM70). The CMs were CO2 activated at 800oC for 1 hour to produced activated carbon monolith electrodes (ACM00, ACM10, ACM30, ACM50 and ACM70). For each percentage of GPC, three duplicate symmetrical supercapacitor cells were fabricated using these activated carbon monolith electrodes respectively, and the capacitive performance amongst the cells was compared and analyzed in order to observe the relationship between the capacitive performance and the physical properties (microstructure and porosity) of the ACMs electrodes containing varying percentage of GPC.
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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.