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With increasing global populations and demand for energy, greater strain is placed on the limited supply of fossil derived fuels, which in turn drives the need for development of alternative energy sources. The discovery of biophotolysis in Chlamydomonas reinhardtii and the development of a spectral-selective photosystem I activating/photosystem II deactivating light (PSI-light) method provides a promising platform for commercial hydrogen production systems. The PSI-light method allows electrons to pass through the photosynthetic electron transport chain while reducing radiation available for photosynthetic oxygen evolution that inactivates hydrogenase. Exploring the physiology of photohydrogen production using the PSI-light method can provide insight on how to optimize conditions for maximum hydrogen production. Through the use of photosynthetic mutant strains of C. reinhardtii, it was possible to suppress photosynthetic oxygen evolution further than using photosystem I light alone to extend photohydrogen production longevity and total yield. A preliminary investigation of an iterating light treatment revealed that longevity and yield could be increased further by providing a period of darkness to allow cells to consume evolved oxygen and resynthesize hydrogenase. Work with these mutants provided understanding that a balance of radiation was required to provide electrons to hydrogenase while limiting oxygen evolution, and that when no light was provided, fermentation of stored starch was the major contributor of electrons to hydrogen production. To determine the role of starch during hydrogen production, wild type cells were exposed to different media and light treatments and monitored for starch consumption and hydrogen production. The results indicated that starch was required for hydrogen production in the dark, but for photohydrogen production, starch likely played a minor role in contributing electrons to hydrogenase. The experiments also showed the importance of acetate in the medium during the hydrogen production phase to allow any significant photohydrogen production. The role of acetate was further investigated as a growth medium constituent that stimulates metabolic activity while reducing photosynthetic oxygen evolution when added to cells grown auto- or mixotrophically. By exposing cells to CO₂ during growth, photohydrogen production was significantly increased over cells grown only in the presence of acetate.

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Hydrogen has now become a suitable candidate for alternative energy generation for small scale applications with the aid of fuel cells. On-board production of hydrogen from methane is the most preferred method via a series of catalytic reactions. However, the carbon monoxide (CO) concentrations following these reforming steps is still too high (±1 %) and is detrimental to the anode of the fuel cell. For maximum output and efficiency of the fuel cell CO concentrations must be reduced to less than 10 ppm. Preferential oxidation (PROX) following the water-gas shift reaction is a promising method that could be employed to reduce the CO content in the reformate gas. This project entails the synthesis, characterization and testing of nickel based catalysts for the oxidation of CO in H₂ rich streams, and to dope with Pt to determine the effects of the platinum group metal on the catalyst for this reaction. A series of NiO/Al₂O₃, Pt/Al₂O₃ and Pt/NiO/Al₂O₃ catalysts were prepared by incipient wetness technique. These catalysts were characterized by TGA, ICP-OES, XRD, BET, TPR, TPD, N₂ adsorption desorption isotherms, CO chemisorptions, SEM-EDX and TEM. The catalysts were then tested for the oxidation of CO in H₂ rich streams. XRD patterns of the catalysts indicated the presence of NiO and PtO phases on the respective supports and in situ redox reactions showed catalysts had reversible phase changes (oxide and metallic) that were stable. N2 adsorption-desorption isotherms indicated the presence of mesoporous materials for all catalysts studied. Impregnation of Pt on the NiO/Al₂O₃ catalysts promoted the reduction of the catalyst to lower temperatures. All catalysts were stable for long periods of time in the presence of H₂ at 150 °C. NiO/Al₂O₃ catalysts were not very active for the preferential oxidation of CO within its stipulated temperature ranges giving the highest CO conversion at 290 °C of 11 % with the selectivity towards CO₂ of ± 25 %. The Pt/Al₂O₃ showed much better activity at higher PROX temperatures compared to the NiO/Al₂O₃ with regards to CO conversion and selectivity towards CO₂. The highest CO conversion obtained within the PROX range was ±56 % with a selectivity towards CO₂ of 68 % at 200 °C. The Pt/NiO/Al₂O₃ showed a synergistic effect, with much higher CO₂ selectivity and CO conversion within the PROX temperature ranges compared to both mono-metallic catalysts studied. The highest CO conversion obtained for this catalyst was at 180 °C of 99.9 % with a selectivity towards CO₂ of 74 %. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2012.

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Although galaxy interactions cause dramatic changes, galaxies also continue to form stars and evolve when they are isolated. The dark matter (DM) halo may influence this evolution since it generates the rotational behaviour of galactic disks which could affect local conditions in the gas. Therefore we study neutral hydrogen kinematics of non-interacting, nearby spiral galaxies, characterising their rotation curves (RC) which probe the DM halo; delineating kinematic classes of galaxies; and investigating relations between these classes and galaxy properties such as disk size and star formation rate (SFR). To generate the RCs, we use GalAPAGOS (by J. Fiege). My role was to test and help drive the development of this software, which employs a powerful genetic algorithm, constraining 23 parameters while using the full 3D data cube as input. The RC is here simply described by a tanh-based function which adequately traces the global RC behaviour. Extensive testing on artificial galaxies show that the kinematic properties of galaxies with inclination >40 degrees, including edge-on galaxies, are found reliably. Using a hierarchical clustering algorithm on parametrised RCs from 79 galaxies culled from literature generates a preliminary scheme consisting of five classes. These are based on three parameters: maximum rotational velocity, turnover radius and outer slope of the RC. To assess the relationship between DM content and the kinematic classes, we generate mass models for 10 galaxies from the THINGS and WHISP surveys, and J. Irwin's sample. In most cases mass models using GalAPAGOS RCs were similar to those using traditional ``tilted-ring'' method RCs. The kinematic classes are mainly distinguished by their rotational velocity. We confirm correlations between increasing velocity and B-magnitude, optical disk size, and find earlier type galaxies among the strong rotators. SFR also increases with maximum rotational velocity. Given our limited subsample, we cannot discern a trend of velocity with DM halo properties such as M_halo/M_baryon. Using this strategy on upcoming large databases should reveal relationships between the DM halo and our kinematic classification scheme. If NGC 2841, NGC 3521 and NGC 5055 are understood to have declining RC after further investigation, this cannot be explained by the usual morphology scenarios.

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