The direct methanol fuel cell (DMFC) performance has been improved via two approaches. The first approach reduces methanol crossover in the membrane electrode assemblies (MEAs) by incorporating a methanol barrier layer onto an anode electrode of the MEA. The second approach increases the triple phase boundaries via the modified morphology of catalyst layers in the MEA. Methanol barrier layers containing a composite layer of Nafion/mordenite (MOR), Nafion/zeolite Y (ZY), Nafion/montmorillonite (MMT) or Nafion/titanate (TN) were distributed onto the anode of an MEA. The performance of these MEAs were tested in a single cell DMFC for temperatures between 30-80 °C and methanol concentrations of 1 M-4 M and compared with a standard MEA to identify changes in power output. At 2 M methanol concentration and 80 °C, the MEAs featuring with Nafion/0.50 wt% MMT and Nafion/0.50 wt% TN delivered higher power densities, 19.76% and 26.60%, respectively, than that of standard MEA. The catalyst morphology has been adjusted by the dilution of catalyst ink to prevent an agglomeration of catalyst particles, resulting in the increased triple phase boundaries which are the phases for electrochemical reactions and for the transportation of electron and proton products. The new-standard MEA presented the best improvement in power density of 81.15% over the conventional counterpart at 80 °C and 2 M methanol concentration. This modified procedure was further utilised for MEAs fabrication. Further investigation has been carried out by the selected Nafion/MMT layer. The MMT loading of 0.25 wt%-1.00 wt% were incorporated onto the barrier layer where the Nafion/0.25 wt% MMT layer illustrated the best performance. This MEA attributed the highest power density of 69.14 mW cm⁻² which is 2.76% higher than 67.23 mW cm⁻² of the new-standard MEA at 80 °C and 2 M methanol concentration. The best improvement in power density, 27.09%, was obtained at low temperature and low methanol concentration of 30 °C and 1 M. The power density was 25.30 mW cm⁻² when compare to 19.91 mW cm⁻² of the new-standard MEA. These results suggest that the methanol barrier layer and the modified morphology of catalyst layer accomplish the aim of improving DMFC performance.

Novel composite membrane systems have been devised for use in direct methanol fuel cell (DMFC) with the ultimate aim of improving overall fuel cell performance in terms of achievable power density. The composite membrane system takes the form of a multilayered structure composing of commercial Nafion117 membrane and a novel composite binding layer situated between the anode and the membrane. Within the composite binding layer, inorganic filler particles are evenly dispersed throughout the Nafion matrix presenting a barrier that impedes methanol crossover. Through the current research, three novel membrane electrode assemblies (MEA) have been fabricated, each employing the composite binding layer system with different filler. Mass of filler used is kept constant at 0.5 wt% of Nafion117 membrane. When tested in a DMFC system, the first MEA which utilizes hydrogen form mordenite filler particles yields optimum power density of 60 mW/cm2 with the operation at 90°C, 1M methanol fuel concentration. This represents an improvement of 34.7% compared to the standard MEA which do not include the composite binding layer. Silanefunctionalized hydrogen form mordenite filler is used in the second MEA which yields optimum power density of 64 mW/cm2 at 90°C, 1M methanol, outperforming the standard MEA by 42.5%. The third MEA makes use of TS-1 particles as fillers. This yields an optimum performance of 38 mW/cm2 at 90°C, 1M methanol, a 14.3% reduction in performance compared to the standard. Through the results obtained, it can be deduced that the novel composite binding layer presents a valid approach in reducing methanol crossover, however, the nature of filler particles used exerts a great influence on its performance. Therefore, further research is recommended in exploring new filler materials for use within the composite membrane system.

The direct methanol fuel cell (DMFC) is considered to be a promising power source for portable electronic applications and transportation. At present there are several challenges that need to be addressed before the widespread commercialization of the DMFC technology can be implemented. The methanol electro oxidation reaction is sluggish, mainly due to the strong adsorption of the reaction intermediate carbon monoxide on platinum. Further, methanol crosses over to the cathode, which decreases the fuel utilization and causes cathode catalyst poisoning. Another issue is the accumulation of the reaction product CO₂ (g) in the anode, which increases the Ohmic resistance and blocks reactant mass transfer pathways. A novel anode configuration is proposed to address the aforementioned challenges. An extended reaction zone (thickness = ∼100-300 µm) is designed to facilitate the oxidation of methanol on sites that are not close to the membrane-electrode interface. Thus, the fuel concentration near the membrane may decrease significantly, which may mitigate adverse effects caused by methanol cross-over. The structure of the fibrous electrode, with its high void space, is believed to aid the disengagement of CO₂ gas. In this thesis the first objective was to deposit dispersed nanoparticle PtRu(Mo) catalysts onto graphite felt substrates by surfactant mediated electrodeposition. Experiments, in which the surfactant concentration, current density, time and temperature were varied, were conducted with the objective of increasing the active surface area and thus improving the reactivity of the electrodes with respect to methanol electro-oxidation. The three-dimensional electrodes were characterized with respect to their deposit morphology, surface area, composition and catalytic activity. The second objective of this work was to utilize the catalyzed electrodes as anodes for direct methanol fuel cell operation. The fuel cell performance was studied as a function of methanol concentration, flow rate and temperature by using a single cell with a geometric area of 5 cm². Increased power densities were obtained with an in-house prepared 3D PtRu anode compared to a conventional PtRu catalyst coated membrane. Coating graphite felt substrates with catalytically active nanoparticles and the utilization of these materials, is a new approach to improve the performance of direct fuel cells. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Using glycerol from biodiesel production as a fuel in a microbial fuel cell (MFC) will generate electricity and valuable by-products from what is currently considered waste. This research aims to screen E. coli (W3110, TG1, DH5, BL21), P. freudenreichii (subspecies freudenreichii and shermanii), and mixed cultures enriched from compost (AR1, AR2, AR3) as anodic biocatalysts in a glycerol-oxidizing MFC. Anaerobic fermentation experiments were performed to determine the oxidative capacity of each catalyst towards glycerol. Using an optimized medium for each strain, the highest anaerobic glycerol conversion from each group was achieved by E. coli W3110 (4.1 g/L), P. freudenreichii ssp. shermanii (10 g/L), and AR2 (20 g/L). These cultures were then tested in an MFC system. All three catalysts exhibited exoelectrogenicity. The highest power density was achieved using P. freudenreichii ssp. shermanii (14.9 mW m-2), followed by AR2 (11.7 mW m-2), and finally E. coli W3110 (9.8 mW m-2).

The performance of a phosphoric acid fuel cell reactor, (PAFC), with n-hexadecane, C16H34, canola biodiesel, soybean biodiesel and petroleum diesel fuel has been investigated. Fifteen-hour steady-state operation was achieved with each of the diesel fuels. This is the first extensive study reported in the literature in which n-hexadecane is used directly as the fuel. It is also the first study of a fuel cell operated with petroleum diesel fuel. Identification of steady-state conditions (temperature = 190oC, molar ratio of fuel to water = 414) is significant because it demonstrates that stable fuel cell operation is technically feasible when operating a PAFC with diesel fuels. Degradation in fuel cell performance was observed prior to reaching steady-state. The degradation was attributed to a carbonaceous material forming on the surface of the anode. After treating the anode with water the fuel cell performance recovered. However, the fuel cell performance degraded again prior to obtaining another steady-state operation. Several consistent observations suggested that the carbonaceous material formed from the diesel fuels might be a reaction intermediate necessary for steady-state operation. Finally, the experiments indicated that water in the phosphoric acid electrolyte could be used as the water required for the anodic reaction. The water formed at the cathode could provide the replacement water for the electrolyte, thereby eliminating the need to provide a water feed system for the fuel cell.

The electrical energy output and the performance of a PEM fuel cell is dependent on the ion transfer in the fuel cell. The ion transport mechanism in the electrolyte cell membrane is dependent on the charge site in the membrane. The charge sites increases with an increase in the hydration of the membrane, this shows that the water content of the membrane is important to facilitate the ion transfer in the electrolyte membrane, hence proper management of water is essential to the operation of the PEM fuel cell system, to achieve these a proper balance of the water transport within the PEM fuel cell is needed for the optimum operation of the PEM fuel cell membrane. This work is based on an assessment of the humidity management effect on the performance of the PEM fuel cell. If the fuel cell membrane is over hydrated with water, it results in over flooding of cell membrane, which causes activation losses and H+ ion cross over losses in the fuel cell, and if the membrane is poorly hydrated it results in poor hydration of the membrane which causes concentration loss, and very low ion conductivity. The water balance system of the fuel cell is such that water vapour is present in the air at the inlet, the water is also used for H+ ion transport from the anode to the cathode, the excess water in the cathode is back diffused in to the anode, at the cathode it is also produced from the chemical reaction of the fuel cell, at the exits water it is evaporated at both the anode and cathode of the cell, and finally with the use of water mass balance we determine the mass of the water which is injected into the fuel cell to meet up the water demand for the hydration of the membrane. This work analyses how these parameters, the operating temperature, relative humidity of air, the inlet temperature, the pressure drop in the cell membrane, the operating temperature, the membrane thickness and the stoichiometry of air affects the water content of the cell membrane. The results from this work showed that a proper management of the PEM fuel cell is of central importance to control the membrane hydration and ensure proper performance of the fuel cell.

The main concerns of air travel are the operating costs of general aviation aircraft. Hybrid-electric system design provides a great opportunity for future aircraft models to be environmentally friendly. The Hybrid-electric power propulsion system experienced a growing interest driven by determined targets. Electric technologies have proven promising success to achieve a successful result in the near- and long-term. Combining fuel cells and batteries, this technology can enable a significant reduction in fuel consumption, noise, and emissions. Different types of fuel cells and batteries are proposed and discussed during this work. The Cessna C-172 is a candidate to test the combination of the most promising fuel cells and batteries for a hybridization or complete electrification strategy.

No description available.

Glucose and other carbohydrates are some of the most abundant renewable energy sources in the world. The oxidation of carbohydrates in a fuel cell allows their chemical energy to be converted directly into electrical energy. Viologen has been indentified and shows promising ability as an electron-transfer catalyst or mediator for carbohydrate oxidation in an alkaline carbohydrate fuel cell. Building on the previous results, the objective of this work was to develop an immobilization chemistry of viologen onto an electrode and to investigate the catalytic activity for carbohydrate oxidation in direct carbohydrate fuel cells.The immobilization was achieved by electropolymerizing a novel viologen monomer onto an electrode surface. The novel viologen monomer, which functions as a monosubstituted viologen, was synthesized and isolated in-house. Gold-plated nickel wire and graphite disks were used as the substrates for the electropolymerization. SEM, EDAX, XPS and water-contact-angle measurement were used to verify the formation of the coating on the gold and graphite surfaces. The catalytic activity of the immobilized viologen on graphite disk surface was examined using a fuel-cell-like device. The test was operated within the desired pH range for an operating fuel cell; it was found that the immobilized viologen polymer has a low catalytic activity toward oxidizing carbohydrates. In addition, the electrochemical properties of the novel viologen monomer were investigated by the method of cyclic voltammetry, as well as for that of two aminoviologens synthesized in-house. Redox potentials, diffusion coefficients, and heterogeneous electron-transfer rate constants were determined.

The fuel economy of Fuel Cell Vehicles (FCVs) is affected by various factors such as the fuel cell efficiency, the regenerative energy capturing, the power control strategy, the vehicle driving patterns, the degree of hybridization between fuel cells and energy storage systems, and so on. In this thesis, a new power control strategy is proposed to improve fuel economy for hybrid FCVs considering the fuel cell efficiency and battery energy management. In order to show the power flows due to the proposed power control strategy and analyze the fuel economy, an overall vehicle simulation for three types of FCVs is implemented. The results show that the fuel economy can be improved by operating the fuel cell system within the specified high efficiency region and managing the state of charge (SOC) of the battery for absorbing regeneration energy effectively.