L. Van Dyk

Synthesis and Characterization of Proton Exchange Membrane Using Polystyrene-butadiene Rubber

Abstract The challenges in proton exchange membrane fuel cell research and development are to reduce the production cost of the fuel cell by reducing the membrane cost. This is possible by the development of an alternative membrane from a cheap source having a good prospect in fuel cell application. Sulphonation of locally available polystyrene butadiene rubber was carried out. The sulphonated polymers were characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (HNMR) to verify sulphonation and identify the site available for proton conduction. Thermo gravimetric and differential scanning analyses were also conducted to investigate the thermal stability of the sulphonated polymer. An elemental analyzer was used in analyzing the percentage of sulphur in the sulphonated polymer to determine the ion exchange capacity and degree of sulphonation, while impedance spectroscopy was used to determine the proton conductivity of the synthesized membrane. Results obtained revealed that an increase in weight of polymer reduced the degree of sulphonation while an increase in sulphonation time resulted in an increase in degree of sulphonation. The synthesized membranes in their fully hydrated form were found to have conductivity in the order of 10−3 S/cm, which increases with an increase in temperature and degree of sulphonation. Results of thermal stability further revealed that the synthesized membranes are thermally stable and can be used in high operating temperature fuel cells.

Synthesis of Low Methanol Permeation Polymer Electrolyte Membrane from Polystyrene-Butadiene Rubber

In order to find a low cost polymer electrolyte membrane with low methanol cross-over, the development of novel polymer electrolytes have been actively carried out in recent time as alternatives to Nafion®, which is the state-of-the art membrane. The problems associated with these alternative membranes are higher permeability to the fuel, lower proton attraction and thermal stability. This work therefore was focused on synthesizing low methanol permeable membrane with good proton conductvity and thermal stability from locally available polymer (Polystyrene-butadiene rubber). Results obtained revealed that the synthesized membrane exhibited methanol permeation in the ranges of 2.13 × 10−7 to 7.58 × 10−7 mol/cm2s which was lower than that of Nafion® (3.15 × 10−6 cm2/s). The proton conductivity of the synthesized membrane is in the order of 10−2 S/cm. The results also show that water and solvent uptake of the synthesized membrane are moderate as compared to that of Nafion®. These results are influenced by the degree of sulphonation and membrane thickness ranging from 0.112 mm−0.420 mm.

Extraction of Scandium (Sc) Using a Task-Specific Ionic Liquid Protonated Betaine Bis(Trifluoromethylsulfonyl)Imide [Hbet][Tf 2 N]

The extraction of scandium from its oxide with a task specific ionic liquid [Hbet][Tf2N] offers potential advantages of lower energy consumption, recycling of the extractant and reduced environmental impact compared to conventional methods. In this paper, the influence of reaction temperature, solid to liquid ratio and water to the ionic liquid ratio on the extraction of scandium from a synthetic scandium oxide (Sc2O3) system was studied. The influence of investigated parameters on leaching was very significant as approximately 98% scandium was extracted from its oxide after 72 h. Furthermore, the ionic liquid also selectively extracted 47% scandium after 48 h from a mixture of pure metal oxides containing oxides of tantalum, niobium, and scandium. The research demonstrated the potential of [Hbet][Tf2N] to selectively extract scandium from columbite processing tailings and other scandium bearing ores like Ixiolite, Heftetjernite and Tantalite which predominately contain tantalum and niobium.

The Synthesis of Proton Conducting Membranes from Polystyrene Butadiene Rubber for Fuel Cell Application: The Effect of Sulphonating Agents on the Membrane Characteristics

Abstract Out of the three major components (membrane, electrocatalyst, and bipolar plates) of proton exchange membrane fuel cell, the cost of the polymer electrolyte membrane is the highest. Therefore, reduction in cost of the membrane will help in reducing the cost of the fuel cell. This work aims at investigating the effect of sulphonating agents (sulphuric acid, acetyl sulphate, and chlorosulphonic acid) on the quality of the membranes synthesized from polystyrene butadiene rubber, which is locally available in South Africa for fuel cell application. The synthesized membranes are characterized by its ion exchange capacity, degree of sulphonation, morphology, thermal stability, and proton conductivity. Analysis of the results obtained reveal that sulphonation with chlorosulphonic acid yields a good membrane with degree of sulphonation in the range of 5.52–31.11%. The synthesized membranes in their fully hydrated form have proton conductivities in the range of 10−3–10−2 S/cm, which increases with increase in temperature. The results of the thermal stability revealed that membranes synthesized with chlorosulphonic acid are thermally stable up to 320°C, which is suitable for the high operating temperature fuel cell. Results of the electrochemical performance of the synthesized membrane in a single fuel cell stack further revealed that the membrane synthesized with chlorosulphonic acid shows better performance (maximum power density of 41.94 mW/cm2) than the membrane synthesized with acetylsulphate (maximum power density of 11.86 mW/cm2).