Ibrahim Abu Talib

Preparation of highly porous binderless activated carbon electrodes from fibres of oil palm empty fruit bunches for application in supercapacitors

Fibres from oil palm empty fruit bunches, generated in large quantities by palm oil mills, were processed into self-adhesive carbon grains (SACG). Untreated and KOH-treated SACG were converted without binder into green monolith prior to N2-carbonisation and CO2-activation to produce highly porous binderless carbon monolith electrodes for supercapacitor applications. Characterisation of the pore structure of the electrodes revealed a significant advantage from combining the chemical and physical activation processes. The electrochemical measurements of the supercapacitor cells fabricated using these electrodes, using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge techniques consistently found that approximately 3h of activation time, achieved via a multi-step heating profile, produced electrodes with a high surface area of 1704m(2)g(-1) and a total pore volume of 0.889cm(3)g(-1), corresponding to high values for the specific capacitance, specific energy and specific power of 150Fg(-1), 4.297Whkg(-1) and 173Wkg(-1), respectively.

Effect of element additions on wear property of eutectic aluminium-silicon alloys

Abstract The effects of cerium, zinc and zirconium additions and subsequent heat treatment on wear of the eutectic aluminium-silicon alloys have been investigated in dry sliding against a steel counterface by using a pin-on-disc machine. Wear surfaces and debris were examined by scanning electron microscopy. Wear characteristics of both binary Al-Si alloys and a commercial LM 13 alloy, were also studied and compared with those of the AlSi alloy containing the Ce, Zn and Zr. The k-values of the ALSI (Al-12.3%Si), LM13, ASMC-1 (Al-12.3%Si-0.75%Mg-0.26%Ce) and ASMC-1 (heat-treated) obtained are 5.795 × 10−4, 4.750 × 10−4, 4.311 × 10-4 and 3.981 × 10−4 mm3N−1 m−1, respectively.

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.

Optical properties of MoO3 thin films for electrochromic windows

Molybdenum oxide thin films have been used in microbatteries and other ionic devices. This paper reports the preparation of MoO3 by electron beam evaporation technique. The films were deposited onto glass substrates at temperatures in the range of 100–250°C. The films were characterized by studying their structure, electrical and optical properties. The films formed at 100°C are amorphous with conductivity of about 2.5×10−5 Ω−1 cm−1. The absorption spectrum of MoO3 doped with LiO2 varies with dopant which suggests that MoO3 is suitable for electrochromic films.The effect of deposition temperature on the optical and electrical properties of the films are discussed.

Characterizations of Cuprous Oxide Thin Films Prepared by Sol-Gel Spin Coating Technique with Different Additives for the Photoelectrochemical Solar Cell

Cuprous oxide (Cu2O) thin films were deposited onto indium tin oxide (ITO) coated glass substrate by sol-gel spin coating technique using different additives, namely, polyethylene glycol and ethylene glycol. It was found that the organic additives added had a significant influence on the formation of Cu2O films and lead to different microstructures and optical properties. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and ultraviolet-visible spectroscopy (UV-Vis). Based on the FESEM micrographs, the grain size of film prepared using polyethylene glycol additive has smaller grains of about 83 nm with irregular shapes. The highest optical absorbance film was obtained by the addition of polyethylene glycol. The Cu2O thin films were used as a working electrode in the application of photoelectrochemical solar cell (PESC).

Supercapacitor Electrodes from Activated Carbon Monoliths and Carbon Nanotubes

Binderless monoliths of supercapacitor electrodes were prepared by the carbonization (N2) and activation (CO2) of green monoliths (GMs). GMs were made from mixtures of self-adhesive carbon grains (SACG) of fibers from oil palm empty fruit bunches and a combination of 5 & 6% KOH and 0, 5 & 6% carbon nanotubes (CNTs) by weight. The electrodes from GMs containing CNTs were found to have lower specific BET surface area (SBET). The electrochemical behavior of the supercapacitor fabricated using the prepared electrodes were investigated by electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). In general an addition of CNTs into the GMs reduces the equivalent series resistance (ESR) value of the cells. A cell fabricated using electrodes from GM with 5% CNT and 5% KOH was found to have the largest reduction of ESR value than that from the others GMs containing CNT. The cell has steeper Warburgs slope than that from its respective non-CNT GM, which reflect the smaller resistance for electrolyte ions to move into pores of electrodes despite these electrodes having largest reduction in specific BET surface area. The cell also has the smallest reduction of specific capacitance (Csp) and maintains the specific power range despite a reduction in the specific energy range due to the CNT addition.

Selective Detection of Dopamine in the Presence of Uric Acid Using Polymerized Phthalo Blue Film Modified Carbon Paste Electrode

A convenient and useful method for the voltammetric determination of dopamine (DA) and uric acid (UA) based on poly (Phthalo blue) modified carbon paste electrode (PTBMCPE) is reported in this paper. The PTBMCPE exhibits excellent electro-catalytic activities for the oxidationreduction of DA and UA, as well as eliminating the interference. Factors influencing the detection processes are optimized and the kinetic parameters are calculated. The effects of pH, scan rate and concentration of dopamine on the peak current were investigated, and the results indicated that the peak current of dopamine is the highest in 0.2 M pH 7.0 Phosphate buffer solution (PBS) and the electrode reaction corresponds to a rate-controlled process. The proposed method possesses the distinct advantages of simple, appropriate for operation, good reproducibility and highly selective and sensitive.

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.

Binderless Composite Electrode Monolith from Carbon Nanotube and Biomass Carbon Activated by H2SO4 and CO2 Gas for Supercapacitor

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.

Electrochromism of copper phthalocyanine thin films

Copper phthalocyanine thin films were deposited using a vacuum evaporation technique at 2 different substrates temperatures of 30 °C and 15 °C. Their electrochromic behaviour in a lithium perchlorate solution was examined. The films deposited at the substrate temperature of 30 °C were polycrystalline, and did not exhibit colour changes under the bias potential of 2.0 V. However, the thin films deposited at the substrate temperature of 15 °C were amorphous and showed colour changes from dark blue to purple and to light blue under the bias potential of 1.0 V.