Ramli Omar

Investigation of the bulk conductivity of BaZr0.95M0.05O3-α (M = Al, Er, Ho, Tm, Yb and Y) under wet N2

Samples of BaZr0.95M0.05O3-α (where M = Al, Er, Ho, Tm, Yb and Y) were prepared by solid state reaction method. The bulk conductivity of the specimens under wet N2 exposure was studied as a function of temperature, dopant ionic radius and the electronegativity of dopants. The correlation between the conductivity and electronegativity of the dopant, which has not been reported in any other studies, will be discussed.

Electrical Conductivity of Carbon Pellets from Mixtures of Pyropolymer from Oil Palm Bunch and Cotton Cellulose

Self-adhesive carbon grains (sacg1) and heat-treated kraft lignin (htkl) were prepared from the oil palm empty fruit bunch, a potential precursor for carbon products due to its large availability from palm oil mills, and sacg was prepared from cellulose (sacg2). Pellets were prepared from mixtures of sacg1 and htkl, as well as sacg1 and sacg2, with varying percentages of htkl (Phtkl%) and sacg2 (Psacg2%). After carbonization up to 1000°C, the measured electrical conductivities, σ (Ωcm)-1, of the respective pellets follow the equations σ=4.13Phtkl+2.43 and σ=0.53Psacg2+2.55, respectively, indicating that htkl has improved in its conducting phase compared to sacg2.

Effect of Compression Pressure on the Physical and Electrochemical Properties of Activated Carbon Monoliths Electrodes for Supercapacitor Application

Green Monoliths (GMs) of self-adhesive carbon grain from fibers of oil palm empty fruit bunches were prepared by compression pressure at 1.43 × 107, 1.91 × 107 and 2.39 × 107 kg/m2, respectively. Activated carbon monoliths ACM-A, ACM-B and ACM-C prepared by CO2 activation from these GMs, respectively, were used as electrodes in supercapacitor cells which employed stainless steel 316L current collector and H2SO4 electrolyte. Evaluation of the electrochemical properties showed that ACM-A, ACM-B and ACM-C cells had specific capacitance of 30, 9 and 5 F/g, total ESR of 3.21, 4.95 and 7.33 Ω, specific power (maximum) of 173.41, 107.58 and 33.82 W/kg, and specific energy (maximum) of 0.67, 0.15 and 0.09 Wh/kg. These properties are directly associated with the surface area of the ACMs, i.e. 419, 336 and 302 m2/g for the ACM-A, ACM-B and ACM-C, respectively, indicating a direct effect of compression pressure on the physical and electrochemical properties of ACMs electrodes.

Study of proton conduction in thulium-doped barium zirconates at high temperatures

The specimens of BaZr1-xTmxO3-α (x = 0.02, 0.05, 0.10 and 0.15, α = x/2) have been prepared and characterized. The formation of the single perovskite phase in the samples was checked by x-ray diffraction. For the verification of the possible charge carriers in the sintered BaZr1-xTmxO3-α samples, three different electrochemical cell measurements were carried out. The measurements of electromotive force (emf) of hydrogen and steam concentration cells showed that the BaZr1-xTmxO3-α ceramic is a protonic conductor and the measurements of emf of the oxygen concentration cell showed that the BaZr0.90Tm0.10O3-α sample exhibited poor oxide ion conduction. Proton transport number tH was calculated and was found to be dependent on the content, x. The BaZr0.90Tm0.10O3-α sample showed the highest value of proton transport number in the temperature range 500≤T≤900 °C.

Graphene/semicrystalline-carbon derived from amylose films for supercapacitor application

Graphene/semicrystalline-carbon in the form of carbon flakes is produced by carbonization up to 600, 700, 800, 900 and 1000°C, respectively, of the amylose films prepared by a casting method on copper foil substrate. The carbon flakes are characterized by X-ray diffraction (XRD) method to determine their microcrystallite interlayer spacing, width and stack-height; and Raman spectroscopy (RS) method to obtain structural information from the D-, D2- and G-bands peak-intensities. The XRD results show that increase in carbonization temperature lead to ~(1-3%), ~85% and ~30%increase in the microcrystallites interlayer spacing, width and stack-height, respectively, indicating that a larger growth of microcrytallite of carbon flakes occurs in the direction parallel to (001) plane or film planar surface. The specific surface area of carbon flakes estimated from the XRD results in decreases from ~4400 to ~3400 m2/g, corresponding to the specific capacitance between ~500 to ~400 F/g, which are well within the range of specific capacitance for typical electrodes carbon for supercapacitor application. The RS results show that the multilayer graphene co-exist with semicrystalline- carbon within the carbon flakes, with the multilayer graphene relative quantities increase with increasing carbonization temperature.

Carbon/Carbon Nanotubes (CNTs) Composites from Green Pellets Contain CNTs and Self‐adhesive Carbon Grains from Fibres of Oil Palm Empty Fruit Bunch

Nano composites green pellets (GPs) were prepared from the mixtures of carbon nanotubes (CNTs) at varying percentage (0, 2, 4, 6, 8 and 10%) and self‐adhesive carbon grains (SACG) from fibres of oil palm empty fruit bunch. These GPs were carbonized and CO2 activated to produce activated carbon/CNTs composites in the form of pellets (ACPs). It was found that the density (ρ) and electrical conductivity (σ) of the ACPs varied nonlinearly with CNTs content; as for the CNTs content of 3–5%, we observed the peak values of ρ and σ at 1.3781 gcm−3 and 3.4146 (Ωcm)−1 respectively. The presence of the agglomerated and individual particles of CNTs in the pores of the ACPs was clearly shown by the micrograph of the Field Emission Scanning Electron Microscope (FESEM). The nitrogen adsorption isotherm data showed the decrease in surface area, volume and diameter of pores due to the effect of CNTs. The effect of CNTs on the electrochemical behavior of the ACPs were investigated from the supercapacitor cells fabricated u...

Review of Energy and Power of Supercapacitor Using Carbon Electrodes from Fibers of Oil Palm Fruit Bunches

Energy and power capability of a supercapacitor is important because of its function to provide backup power or pulse current in electronic/electric products or systems. The choice of its electrode materials, typically such as carbon, metal oxide or conducting polymer determines the mechanism of its energy storage process. This short review focuses on the supercapacitors using porous carbon electrode prepared, respectively, from fibers of oil palm empty fruit bunches. The specific energy and specific power of these supercapacitors were analyzed to observe their trend of change with respect to the electrode preparation parameters affecting the porosity, structure, surface chemistry and electrical conductivity of electrodes, and thence influence the energy and power capability of a supercapacitor. This review found that the trend of change in specific energy and specific power was not in favor of the expectation that both the specific energy and specific power should be in increasing trend with a significant progress.

Effect of KOH Treated Graphene in Green Monoliths of Pre-Carbonized Biomass Fibers on the Structure, Porosity and Capacitance of Supercapacitors Carbon Electrodes

Activated carbon monoliths (ACMs) electrodes for supercapacitor application were prepared from the green monoliths (GMs) containing KOH treated self-adhesive carbon grains (SACG) added with KOH treated graphene at its weight percentages of 0, 2, 4, 6, 8 and 10 %, respectively. The SACG were prepared from fibers of oil palm empty fruit bunches by a low carbonization temperature method. The ACMs were produced by the carbonization and activation of the GMs. The surface area, structure and specific capacitance of the ACMs electrodes were found affected by the graphene addition. The highest surface area of the ACMs electrode was observed for the addition of 6% graphene, which corresponds to the carbon turbostratic structure of the ACMs electrodes with the values of its crystallites interlayers spacing (d002 and d100) at 0.352 nm and 0.205 nm, and its crystallites stack-width (La) and stack-height (Lc) at 43.21 nm and 10.06 nm, respectively. The specific capacitance of the cell using this electrode was 112 F / g.

Electric double-layer capacitors with tea waste derived activated carbon electrodes and plastic crystal based flexible gel polymer electrolytes

We report a novel configuration of symmetrical electric double-layer capacitors (EDLCs) comprising a plastic crystalline succinonitrile (SN) based flexible polymer gel electrolyte, incorporated with sodium trifluoromethane sulfonate (NaTf) immobilised in a host polymer poly (vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP). The cost-effective activated carbon powder possessing a specific surface area (SSA) of ~ 1700 m2g-1 containing a large proportion of meso-porosity has been derived from tea waste to use as supercapacitor electrodes. The high ionic conductivity (~3.6×10-3 S cm-1 at room temperature) and good electrochemical stability render the gel polymer electrolyte film a suitable candidate for the fabrication of EDLCs. The performance of the EDLCs has been tested by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge-discharge studies. The performance of the EDLC cell is found to be promising in terms of high values of specific capacitance (~270 F g-1), specific energy (~ 36 Wh kg-1), and power density (~ 33 kW kg-1).

AC-Conductivity and proton transport number of BaZr0.90Al0.10O3-δ

AC-conductivity measurements of BaZr0.90Al0.10O3−δ (where δ describes the number of oxygen ion vacancies per unit cell) in wet and dry N2 have been carried out over the temperature range from 400 to 900 °C. Both atmospheres showed the usual Arrhenius behavior of BaZr0.90Al0.10O2.95. The proton transport number,tH, was also determined from the conductivity measurements of BaZr0.90Al0.10O2.95 in wet and dry N2 and takes up values of 0.97 and 0.78 in the temperature range 400 – 900 °C, respectively.