Magister Scientiae - MSc / Metal hydrides hydrogen storage materials have the ability to reversibly absorb and release large amounts of hydrogen at low temperature and pressure. In this study, metal hydride materials employed as negative electrodes in Ni-MH batteries are investigated. Attention is on AB5 alloys due to their intermediate thermodynamic properties. However, AB5 alloys a have tendency of forming oxide film on their surface which inhibits hydrogendissociation and penetration into interstitial sites leading to reduced capacity. To redeem this, the materials were micro-encapsulated by electroless deposition with immersion in Pd and Pt baths. PGMs were found to increase activation, electrochemical activity and H2 sorption kinetics of the MH alloys. Between the two catalysts the one which displayed better performance was chosen. The materials were characterized by X-ray difractommetry, and the alloys presented hexagonal CaCu 5–type structure of symmetry P6/mmm. No extra phases were found, all the modified electrodes displayed the same behavior as the parent material. No shift or change in peaks which corresponded to Pd or Pt were observed. Scanning Electron Microscopy showed surface morphology of the materials modified with Pd and Pt particles, the effect of using different reducing agents (i.e ., N2H4 and NaH2PO2), and alloys functionalized with γ-aminosopropyltrietheosilane solution prior to Pd deposition. From all the surface modified alloys, Pt and Pd particles were observed on the surface of the AB5 alloys. Surface modification without pre-functionalization had non-uniform coatings, but the pre- functionalized exhibited more uniform coatings. Energy dispersive X-ray Spectroscopy and Atomic Absorption Spectroscopy determined loading of the Pt and Pd on the surface of all the alloys, and the results were as follows: EDS ( Pt 13.41and Pd 31.08wt%), AAS (Pt 0.11 and Pd 0.78wt%). Checking effect of using different reducing agents N2H4 and NaH2PO2 for electroless Pd plating the results were as follows: EDS (AB5_N2H4_Pd- 7.57 and AB 5_NaH2PO2_Pd- 31.08wt%), AAS (AB5_N2H4_Pd- 11.27 and AB5_NaH2PO2_Pd- 0.78wt%). For the AB5 alloyspre-unctionalized with γ-APTES, the results were: EDS (10.24wt%) and AAS (0.34wt%). Electrochemical characterization was carried out by charge/discharge cycling controlled via potential to test the AB5 alloy. Overpotential for unmodified, Pt and Pd modified electrodes were-1.1V, -1.24V, and -1.60V, respectively. Both modified electrodes showed discharge overpotentials at lower values implying higher specific power for the battery in comparison with the unmodified electrodes. However, Pd electrode exhibited higher specific power than Pt. To check the effect of the reducing agent the results were as follows: AB5_ N2H4_Pd (0.4V) and AB5_NaH2PO2_Pd (-0.2V), sodium hypophosphite based alloy showing lower overpotential values, implying it had higher specific power than hydrazine based bath. Alloy pre-functionalized with γ-APTES, the overpotential was (0.28V), which was higher than -0.2V of the alloy without pre-functionalization, which means pre-functionalization with γ-APTES did not improve the performance of the alloy electrode. Polarization resistance of the electrodes was investigated with Electrochemical Impedance Spectroscopy. The unmodified alloy showed high resistance of 21.6884 while, both Pt and Pd modified electrodes exhibited decrease 14.7397 and 12.1061 respectively, showing increase in charge transfer for the modified electrodes. Investigating the effect of the reducing agent, the alloys exhibited the following results: (N2H497.8619 and NaH2PO212.1061 ) based bath. Alloy pre-functionalized with γ-APTES displayed the resistance of 9.3128. Cyclic Voltammetry was also used to study the electrochemical activity of the alloy electrodes. The voltammograms obtained displayed the anodic current peak at -0.64V to -0.65V for the Pt and Pd modified electrodes, respectively. Furthermore, the electrode which was not coated with Pt or Pd the current peak occurred at -0.59V. The Pd and Pt coated alloy electrodes represented lower discharge overpotentials, which are important to improve the battery performance. Similar results were also observed with alloy electrodes Pd modified using N2H4(-0.64V) and NaH2PO2(-0.65V). For the electrode modified with and without γ-APTES the over potentials were thesame (-0.65V). PGM deposition has shown to significantly improve activation and hydrogen sorption performance and increased the electro-catalytic activity of these alloy electrodes. Modified electrodes gave better performance than the unmodified electrodes. As a result, Pd was chosen as the better catalyst for the modification of AB5 alloy. Based on the results, it was concluded that Pd electroless plated using NaH2PO2 reducing agent had better performance than electroless plating using N2H4 as the reducing agent. Alloy electrode pre-functionalized with γ-APTES gave inconsistent results, and this phenomenon needs to be further investigated. In conclusion, the alloy modified with Pd employing NaH 2PO2 usased electroless plating bath exhibited consistent results, and was found to be suitable candidate for use in Ni-MH batteries / South Africa

The research objectives for this study involved the development of a modified thermophilic fluidized bacterial granular bed bioreactor system for the production of biohydrogen from sucrose. The granules were comprised of an undefined anaerobic thermophilic multispecies consortium of bacteria. In order to establish the thermophilic bacterial granules, the bioreactor was operated as a chemostat under increasing dilution rates. This promoted the selection and enrichment of thermophilic granules comprised of a multispecies bacterial consortium. Endo medium which is one of the most basic bacteriological nutrient mediums was used as the nutrient supply in the granule generating chemostat experiments. Bacterial inoculums from mesophilic environments were used to induce and establish thermophilic and extreme-thermophilic adapted bacterial granules in the chemostat experiments. Granulation was successfully induced under a thermophilic temperatures ranging from 55 oC to 70 oC within a period ranging from 5 to 14 days. Bioreactor design and operation was modified so as to increase both hydrogen yield (HY) and volumetric hydrogen productivity (HP). It was found that in order to increase both HY and HP it was necessary to implement a number of modifications in bioreactor design and operation. The two key operational parameters were temperature and de-gassed effluent recycling rate through the bioreactor bed. Through the incorporation of a solid-liquid separator in the form of 11.6 L settling column, bacteria granular bed wash out was prevented for a 5.0 L thermophilic bioreactor system operated at high volumetric biomass densities, low hydraulic retention times and high degassed effluent recycle rates. Stability of the bioreactor operation in terms of volumetric hydrogen productivity (L H2/L/h), %H2 content and pH maintenance was readily maintained for 50 days. While volumetric hydrogen productivity increased with bacterial biomass density, both hydrogen yield (mol H2/mol glucose) and specific hydrogen productivity (L H2/g/h) declined with increasing biomass density. In this process the rate of physical removal of H2 trapped in the bulk liquid phase surrounding the fluidized granules reduced the thermodynamic constraints preventing the simultaneous achievement of high HPs and high HYs in a granular fluidized bed derived from an undefined bacterial culture. It became evident that a thermophilic temperature alone was an insufficient condition to achieve simultaneously high HPs and high HYs. It also became evident that hydraulic retention time for degassed effluent recycling was a critical for the simultaneous achievement of high HPs and high HY. It was discovered that a reduction in the total volume of bioreactor system relative to increasing rates of degassed effluent recycle was a necessary condition for the simultaneous achievement of both high HPs and high HYs. Thus at thermophilic temperatures any increase in the bioreactor system volume should also be accompanied by a concomitant increase in the rate of degassed effluent recycling so the HRT always remained below the critical threshold necessary for the simultaneous achievement of high HPs and high HYs. Once it was demonstrated that by the adjusting bioreactor system volume and the degassed to effluent recycle rates both high HPs and high HYs could be achieved only under thermophilic conditions it was necessary to show that under these operational condition the system would produce net positive work in terms of hydrogen energy production. It was shown through modeling heat exchanges that if the bioreactor was effectively insulated and waste heat was recycled or recovered then net positive work was accomplished by the bioreactor system. Bacterial granules grown from mesophilic inoculant were adapted to generate H2 from sucrose under a range of thermophilic temperatures (55, 60, 65, 70 oC). Attainments of two H2 generation process goals were assessed. First, whether a net positive net energy balance at thermophilic temperatures and high effluent recycle rates were attainable. Secondly, whether the volumetric hydrogen productivities were sufficient to drive a 5 kW fuel cell when scale-up to 1 m3

This thesis discuses two very different projects. In the first project, synthesizing a polymer with the potential to release H2S. This was accomplished through the copolymerization of L-lactide and lactide monomers that has been functionalized with 4-hydroxythiobenzamide which is known to release H2S in vivo. The synthesis of the functionalized monomer required the development of a new method to attach functional groups to a derivative of L-lactide, which involved the addition of a thiol to an alpha- beta-unsaturated lactide using catalytic I2. After polymerization, the molecular weight of the copolymers ranged from 8 to 88 kg mol-1 with PDIs below 1.50. These polymers have the ability to be loaded with different amounts of thiobenzamide by controlling the ratio of the functionalized monomer with L-lactide during polymerization. The copolymers were fabricated into two sizes of microparticles with average diameters of 0.52 and 12 µm. The degradation of the smaller microparticles was studied in a PBS buffered solution at pH 7.4 which showed the slow release of the thiobenzamide over a 4 week period. These microparticles are the first to show potential to deliver H2S over a period of weeks. This research addresses a critical need in the field of H2S in medicine where no method exists to release H2S in vivo at times over a few hours. In the second project dicyclopentadiene was polymerized with Grubbs first generation catalyst and fabricated into highly cross-linked membranes with a thickness of 100 µm. The flux of twenty-one molecules with varying polarities and molecular weights ranging from 101 to 583 g mol-1 were studied. Molecules that permeated these membranes had flux rates of 10-5 to 10-6 mol cm-2 h-1 but molecules that did not permeate these membranes had flux rates 104 to 105 times slower. The large difference in flux did not have a strong correlation to molecular weight or solubility in the membrane. However, there was a strong correlation to the cross-sectional areas of the molecules. Cross-sectional area is the smallest two-dimensional rectangle determined by molecular modeling. The cross-sectional area cut-off of the membranes was determined to be between 0.38 and 0.50 nm2. This property gives these membranes the selectivity to successfully separate constitutional isomers, such as tributylamine and triisobutylamine. The membranes have also been used to separate organic products from expensive catalyst and ligands as well as different fatty acids from each other as their respective amine salts.

<p>Abstract</p><p>Motor sports have been around as long as motor vehicles have been. Sports are often seen as costly polluter but in the same time the motor sports have encourages a large part of development, both for vehicles and other industries. Inventions like rear mirror and ABS brakes come from motor sports. </p><p>One way to once again drive development forward while making motor sports carbon-neutral is to run the race cars on hydrogen. </p><p>In this thesis, the goal is to convert a spark ignition engine for hydrogen operation. The basis for the hydrogen conversion is the current situation analysis, which raises questions about racing, safety, economy and technology. </p><p>In the current situation the most hydrogen are made from natural gas reforming, giving a net increase of carbon dioxide in the atmosphere. The technology and the desire are to produce hydrogen from all eco-friendly sources such as hydro, solar and wind power. Today, hydrogen is stored efficiently in 700 bars composite tanks. </p><p> This thesis shows how easy most diesel, wankel or spark ignition engines can be converted to hydrogen. Our engine has been converted through the reconstruction of ignition and fuel systems for hydrogen.</p><p>One possible scenario for hydrogen racing is to use professor Stenmark hydrogen balls (macro-spheres) in a piping system in the car. As the macro-spheres can be easily inserted in the pipe, the safety, space and emphasis in the car improved significantly against other storage methods of hydrogen. Today there are no race classes for hydrogen vehicles, but in the future, hydrogen vehicles can perhaps compete on equal terms or in their own classes.</p>

Thesis (Ph. D.)--University of Washington, 1983. / Vita. Includes bibliographical references.

Thesis (M.S.)--Oregon Graduate Center, 1972.

M.S. / Chemistry / The present investigation concerns itself with the study of the pressure dependence of hydrogen adsorption on a platinum electrode in acid media. The specific intent of this work is to find whether additional hydrogen adsorbs onto a platinum electrode when the system pressure is increased. Through this means it is possible to prove or disprove the assumption usually made that hydrogen forms a monolayer on a platinum electrode at one atmosphere pressure. Secondary aspects of this study are the effects of diffusion of hydrogen atoms into the electrode bulk, and the desorption and diffusion of hydrogen molecules into the solution layer surrounding the electrode.

<p>Metal hydrides hydrogen storage materials have the ability to reversibly absorb and release large amounts of hydrogen at low temperature and pressure. In this study, metal hydride materialsemployed as negative electrodes in Ni-MH batteries are investigated. Attention is on AB5 alloys due to their intermediate thermodynamic properties. However, AB5 alloys a have&nbsp / tendency of forming oxide film on their surface which inhibits hydrogen dissociation and penetration into interstitial sites leading to reduced capacity. To redeem this, the materials were micro-encapsulated by electroless deposition with immersion in Pd and Pt baths. PGMs were found to increase activation, electrochemical activity and H2 sorption kinetics of the MH alloys. Between the two catalysts the one which displayed better performance was chosen. The materials were characterized by X-ray difractommetry, and the alloys presented hexagonal CaCu5 &ndash / type&nbsp / structure of symmetry P6/mmm. No extra phases were found, all the modified electrodes displayed the same behavior as the parent material. No shift or change in peaks which corresponded to Pd or Pt were observed. Scanning Electron Microscopy showed surface morphology of the materials modified with Pd and Pt particles, the effect of using different reducing agents (i.e., N2H4 and NaH2PO2), and alloys functionalized with &gamma / -aminosopropyltrietheosilane solution prior to Pd deposition. From all the surface modified alloys, Pt and Pd particles were observed on the&nbsp / surface of the AB5 alloys. Surface modification without pre-functionalization had non-uniform coatings, but the prefunctionalized exhibited more uniform coatings. Energy dispersive X-ray Spectroscopy and Atomic Absorption Spectroscopy determined loading of the Pt and Pd on the surface of all the alloys, and the results were as follows: EDS ( Pt 13.41 and Pd 31.08wt%), AAS (Pt 0.11 and Pd 0.78wt%). Checking effect of using different reducing agents N2H4 and NaH2PO2 for electroless Pd plating the results were as follows: EDS (AB5_N2H4_Pd- 7.57 and AB5_NaH2PO2_Pd- 31.08wt%), AAS (AB5_N2H4_Pd- 11.27 and AB5_NaH2PO2_Pd- 0.78wt%). For the AB5 alloys pre-functionalized with &gamma / -APTES, the results were: EDS (10.24wt%) and AAS (0.34wt%). Electrochemical characterization was carried out by charge/discharge cycling controlled via potential to test the AB5 alloy. Overpotential for unmodified, Pt and Pd modified&nbsp / electrodes were -1.1V, -1.24V, and -1.60V, respectively. Both modified electrodes showed discharge overpotentials at lower values implying higher specific power for the battery in comparison with the unmodified electrodes. However, Pd electrode exhibited higher specific power than Pt. To check the effect of the reducing agent the results were as follows: AB5_ N2H4_Pd (0.4V) and AB5_NaH2PO2_Pd (-0.2V), sodium hypophosphite based alloy showing lower overpotential values, implying it had higher specific power than hydrazine based bath. Alloy prefunctionalized with &gamma / -APTES, the overpotential was (0.28V), which was higher than -0.2V of the alloy without pre-functionalization, which means pre-functionalization with &gamma / -APTES did not improve the performance of the alloy electrode. Polarization resistance of the electrodes was investigated with Electrochemical Impedance Spectroscopy. The unmodified alloy showed high resistance of&nbsp / 21.6884 while, both Pt and Pd modified electrodes exhibited decrease 14.7397 and 12.1061 respectively, showing increase in charge transfer for the modified electrodes. Investigating the effect of the reducing agent, the alloys exhibited the following results: (N2H4 97.8619 and NaH2PO2 12.1061) based bath. Alloy pre-functionalized with &gamma / -APTES displayed the&nbsp / resistance of 9.3128. Cyclic Voltammetry was also used to study the electrochemical activity of the alloy electrodes. The voltammograms obtained displayed the anodic current peak at -0.64V&nbsp / o -0.65V for the Pt and Pd modified electrodes, respectively. Furthermore, the electrode which was not coated with Pt or Pd the current peak occurred at -0.59V. The Pd and Pt coated&nbsp / alloy electrodes represented lower discharge overpotentials, which are important to improve the battery performance. Similar results were also observed with alloy electrodes Pd modified&nbsp / using N2H4 (-0.64V) and NaH2PO2 (-0.65V). For the electrode modified with and without &gamma / -APTES the over potentials were the same (-0.65V). PGM deposition has shown to significantly&nbsp / improve activation and hydrogen sorption performance and increased the electro-catalytic activity of these alloy electrodes. Modified electrodes gave better performance than the unmodified&nbsp / electrodes. As a result, Pd was chosen as the better catalyst for the modification of AB5 alloy. Based on the results, it was concluded that Pd electroless plated using NaH2PO2 reducing agent&nbsp / had better performance than electroless plating using N2H4 as the reducing agent. Alloy electrode pre-functionalized with &gamma / -APTES gave inconsistent results, and this phenomenon needs to&nbsp / be further investigated. In conclusion, the alloy modified with Pd employing NaH2PO2 based electroless plating bath exhibited consistent results, and was found to be suitable candidate for&nbsp / use in Ni-MH batteries.</p>

The endothelial layer of blood vessels is able to produce a number of vasoactive substances, and these substances can work to either relax or contract the underlying vascular smooth muscle. A hallmark of hypertension is the development of endothelial dysfunction, a shift in the balance of these substances to a state of increased contraction. Hydrogen sulfide (H2S) has recently garnered much interest as a gaseous signaling molecule with the discoveries that is can relax isolated blood vessels and lower blood pressure in young spontaneously hypertensive rats (SHR). Here we investigate whether chronic H2S treatment (56 μmol/kg of the H2S donor sodium hydrosulfide (NaHS), once daily for 5 weeks) can lower the blood pressure of adult aged SHR when compared to normotensive control Wistar Kyoto rats (WKY), and whether there are changes in the endothelium-dependent relaxation and contraction pathways. Invasive hemodynamic measurements including systolic, diastolic, and mean blood pressure, as well as heart rate were measured. Isolated vessel myography was performed on the common carotid artery to determine whether there were changes in the endothelium-dependent and independent relaxation and contraction pathways. This was achieved using a number of dose response curves. Changes in endothelium dependent dilation to ACh, VSM sensitivity to NO and H2S, and NO bioavailability were tested with dose response curves using ACh, SNP (an NO donor), H2S and indomethacin, respectively. TP receptor sensitivity, as well as COX-mediated constriction in quiescent vessels was also examined by using the TP receptor agonist U46619 and L-NAME (eNOS inhibitor), respectively. Biochemical analyses included Western blotting to assess protein levels of CSE (H2S generating enzyme) and eNOS (NO generating enzyme) as well as determining prostacyclin production. Determination of H2S concentration in the blood via a sulfide electrode was also performed to confirm that the H2S treatment was effective. There were no main effects of H2S treatment in any of the hemodynamic measurements taken. ACh dose response revealed a blunting in the recontraction at 10-5 and 10-4.5 log M concentrations (p<0.05) in SHR treated with H2S. No effects were observed, however, in any other myography protocol. Western blot analysis revealed no difference in the protein expression of CSE or eNOS with H2S treatment, and there were no differences in prostacyclin production with H2S treatment. In conclusion, these data suggest that H2S may not be an effective treatment for hypertension in adult SHR, in contrast to previous work finding a similar dosing regimen to be effective at lowering blood pressure in young SHR. Further work must be completed to ascertain the mechanism for the alteration in the ACh dose response curve and to determine at what time point the H2S treatment becomes ineffective.

Abstract Motor sports have been around as long as motor vehicles have been. Sports are often seen as costly polluter but in the same time the motor sports have encourages a large part of development, both for vehicles and other industries. Inventions like rear mirror and ABS brakes come from motor sports. One way to once again drive development forward while making motor sports carbon-neutral is to run the race cars on hydrogen. In this thesis, the goal is to convert a spark ignition engine for hydrogen operation. The basis for the hydrogen conversion is the current situation analysis, which raises questions about racing, safety, economy and technology. In the current situation the most hydrogen are made from natural gas reforming, giving a net increase of carbon dioxide in the atmosphere. The technology and the desire are to produce hydrogen from all eco-friendly sources such as hydro, solar and wind power. Today, hydrogen is stored efficiently in 700 bars composite tanks. This thesis shows how easy most diesel, wankel or spark ignition engines can be converted to hydrogen. Our engine has been converted through the reconstruction of ignition and fuel systems for hydrogen. One possible scenario for hydrogen racing is to use professor Stenmark hydrogen balls (macro-spheres) in a piping system in the car. As the macro-spheres can be easily inserted in the pipe, the safety, space and emphasis in the car improved significantly against other storage methods of hydrogen. Today there are no race classes for hydrogen vehicles, but in the future, hydrogen vehicles can perhaps compete on equal terms or in their own classes.