Mohd Hasbi Ab. Rahim

Multiporous nanofibers of SnO2 by electrospinning for high efficiency dye-sensitized solar cells

Various one-dimensional nano-morphologies, such as multiporous nanofibers (MPNFs), porous nanofibers (PNFs), and nanowires (NWs) of SnO2, are synthesized using electrospinning technique by controlling the tin precursor concentration. The MPNFs have ∼8-fold higher surface area compared to the other morphologies. Dye-sensitized solar cells (DSCs) were fabricated using these nanostructures as photoanodes and their performance was compared. The MPNFs surpass the performance of PNFs and NWs as well as conventional TiO2 paste. Record photoconversion efficiency (PCE) of ∼7.4% was realized in MPNFs DSCs, which was twice to that achieved using PNFs (∼3.5%). Furthermore, the MPNFs showed over >80% incident photon to current conversion efficiency (22% higher than that achieved by spherical P25 TiO2 particles) and also demonstrated ∼3 times longer electron lifetime and electron diffusion length. Owing to the possibility to produce large quantities using electrospinning technique, huge commercial potential of SnO2 nanostructures, and promising results achieved herein, the MPNFs are expected soon to be utilized in commercial devices.

An accelerated route of glycerol carbonate formation from glycerol using waste boiler ash as catalyst

Waste boiler ash was successfully utilised as catalyst for the direct synthesis of glycerol carbonate from glycerol and urea. A series of catalysts were prepared using various calcination temperatures. The physico-chemical properties of the catalysts have been investigated by using XRD, BET, TGA, FESEM-EDX, ICP-MS, Hammett test and CO2-TPD. From the study it was found that boiler ash had significant catalytic activity towards conversion of glycerol into glycerol carbonate. It is believed that the potassium metal ion which detaches from potassium silicate had a major impact on the catalytic data where the potassium ion being a weak Lewis acid causes selective catalytic transformation of glycerol into glycerol carbonate. The mechanistic pathway through glycerol carbamate intermediate was confirmed through time online analysis study using 13C-NMR and ATR-FTIR, respectively. However, the selective transformation of glycerol carbamate into glycerol carbonate is reported to be different where it is formed in an accelerated manner. The highest catalytic activity resulted in an average percentage of 93.6 ± 0.4% glycerol conversion, 90.1 ± 1.0% glycerol carbonate selectivity and 84.3 ± 1.1% glycerol carbonate yield. Besides, for the first time the novel idea of using waste material, specifically boiler ash, is proposed as a catalyst for synthesis of glycerol carbonate from glycerol and urea. The current research employed suggests an alternative route for proper disposal of waste boiler ash.

A brief review of para-xylene oxidation to terephthalic acid as a model of primary C-H bond activation

Abstract The oxidation of para-xylene to terephthalic acid has been commercialised as the AMOCO process (Co/Mn/Br) that uses a homogeneous catalyst of cobalt and manganese together with a corrosive bromide compound as a promoter. This process is conducted in acidic medium at a high temperature (175–225 °C). Concerns over environmental and safety issues have driven studies to find milder oxidation reactions of para-xylene. This review discussed past and current progress in the oxidation of para-xylene process. The discussion concentrates on the approach of green chemistry including (1) using heterogeneous catalysts with promising high selectivity and mild reaction condition, (2) application of carbon dioxide as a co-oxidant, and (3) application of alternative promoters. The optimisation of para-xylene oxidation was also outlined.

Environment-Modulated Crystallization of Cu2O and CuO Nanowires by Electrospinning and Their Charge Storage Properties

This article reports the synthesis of cuprous oxide (Cu2O) and cupric oxide (CuO) nanowires by controlling the calcination environment of electrospun polymeric nanowires and their charge storage properties. The Cu2O nanowires showed higher surface area (86 m2 g-1) and pore size than the CuO nanowires (36 m2 g-1). Electrochemical analysis was carried out in 6 M KOH, and both the electrodes showed battery-type charge storage mechanism. The electrospun Cu2O electrodes delivered high discharge capacity (126 mA h g-1) than CuO (72 mA h g-1) at a current density of 2.4 mA cm-2. Electrochemical impedance spectroscopy measurements show almost similar charge-transfer resistance in Cu2O (1.2 Ω) and CuO (1.6 Ω); however, Cu2O showed an order of magnitude higher ion diffusion. The difference in charge storage between these electrodes is attributed to the difference in surface properties and charge kinetics at the electrode. The electrode also shows superior cyclic stability (98%) and Coulombic efficiency (98%) after 5000 cycles. Therefore, these materials could be acceptable choices as a battery-type or pseudocapacitive electrode in asymmetric supercapacitors.

Versatile boiler ash containing potassium silicate for the synthesis of organic carbonates

In this study, boiler ash containing potassium silicate (BA 900) and potassium silicate (K2SiO3) were proven to be feasible Lewis acid catalysts for the synthesis of different organic carbonates (glycerol carbonate, ethylene carbonate, and propylene carbonate) from different polyol (glycerol, ethylene glycol, and propylene glycol) feedstocks. In addition, the developed catalytic reaction has the ability to produce propylene carbonate at milder reaction temperatures. BA 900 and K2SiO3 were reusable for three consecutive reaction cycles without the loss of activity. The reusable characteristics of catalysts were confirmed through several characterisation techniques, i.e. XRD, FTIR, XRF, N2 physisorption, FESEM-EDX, and Hammett test. All organic carbonates synthesised had a similar synthetic mechanistic pathway, which involved decomposition of intermediate carbamates into their respective carbonates.

Assessment of the River Water Pollution Levels in Kuantan, Malaysia, Using Ion-Exclusion Chromatographic Data, Water Quality Indices, and Land Usage Patterns

Water qualities of three suburban rivers, namely, Kuantan, Belat, and Galing rivers, in Kuantan, Malaysia, were examined effectively by using ion-exclusion/cation-exchange chromatography with water quality indices and land usage data. Specifically, we have focused on evaluating and grasping the effect of sewage/household wastewater discharged from housing areas in the Kuantan district on the river water quality. Based on this study, the following beneficial information were obtained effectively: (1) the pollution levels in the three rivers (Kuantan River: Classes I–III, Belat River: Classes I–III, and Galing River: Classes I–V) are linked with the urbanization level of the river basin area; (2) differences in the biological reactions in the different pollution level rivers are understood; (3) Galing River is among the most polluted rivers not only in Kuantan but also in the Peninsular Malaysia, owing to poor water treatment of the sewage/household wastewater discharged from the river basin area.

Transesterification of Karanja (Pongammia Pinnata) oil using barnacle derived CaO mixed ZnO

Karanja oil (Pongamia Pinnata) as non-edible oil is chosen as alternative biodiesel feedstock as comparable diesel fuel prolonged due to the battle of starvation on using of edible oils traditionally. Transesterification reaction of Karanja oil extracted from Soxhlet method and catalysed by barnacle as a CaO source mixed with ZnO through ball mill method at 1:2 ratios, calcined for 3 h at 700 °C successfully to produce biodiesel. The optimal conditions were found to be: methanol/oil mass ratio, 12:1; catalyst amount, 9 wt% at the reaction temperature, 65 °C within 3 h of reaction time achieving 97.75% of methyl ester conversion.