Philosophiae Doctor - PhD / Fuel cells are long term solution for global energy needs. In current fuel cell technologies, Proton Exchange Membrane (PEM) fuel cells are known for quick start-up and ease of operation compared to other types of fuel cells. Operating PEM fuel cells at high temperature show promising applications for stationary combined heat and power application (CHP). The high operating temperature up to 160°C allows waste heat to be recovered for co-generation or tri-generation purposes. The commercially available PEM fuel cells operating at 160⁰C can tolerate up to 3% CO without significant loss of performance, making HT-PEM fuel cell viable choice when reformate is used. In reality these advantages convert to very little balance-of-plant compared to Nafion® based fuel cells operating at 60°C. However, there are some problems that prevent high temperature fuel cells from large scale commercialization. The cathode is said to have sluggish reaction kinetics and high cell potentials and operating temperature during fuel cell start-up may cause severe degradation. The formation of liquid water during the shut-down can cause the phosphoric acid to leach from the cell during operation. Efforts are being made to reduce the cost and increase the durability of fuel cell components (such as catalyst and membrane) at high temperatures. Apart from degradation issues, the problems are related to cost and performance. The performance of the PEM fuel cells depends on a lot of factors such as fuel cell design and assembly, operating conditions and the flow field design used on the cathode and anode plates. The flow field geometry is one important factor influencing the performance of fuel cells. The flow fields have significant effect on pressure and flow distribution inside the fuel cell. A homogeneous distribution of the reactant gases over the active catalyst surface leads to improved electrochemical reactions and thus enhances the performance of the fuel cell. So, the design of flow fields is one of the important issues for performance improvement of PEM fuel cell in terms of power density and efficiency. There are different types of flow fields available for PEM fuel cells such as serpentine, pin, interdigitated and straight flow fields but the most obvious choice is multiple serpentine. The same can be used for high temperature PEM fuel cell (HT-PEMFC) application with ease because of absence of liquid water during the high temperature operation and no need for complex water management.

In order to achieve a more stable and highly proton conducting membrane that is also cost effective, the perfluoroalkyl benzenesulfonylimides (PFSI) polymers are proposed as electrolyte for Proton Exchange Membrane Fuel Cells. 4-(trifluoromethyl)-2-diazonium perfluoro-3, 6-dioxa-4-methyl-7-octene benzenesulfonyl imide (I) is synthesized from Nafion monomer via a 5-step schematic reaction at optimal reaction conditions. This diazonium PFSI zwitterionic monomer can be further subjected to polymerization. The loss of the diazonium N2+ functional group in the monomer is believed to form the covalent bond between the PFSI polymer electrolyte and carbon electrodes support. All the intermediates and final products were characterized using 1H NMR, 19F NMR and IR spectrometry.

One diazonium (perfluoroalkyl) benzenesulfonimide monomer, perfluoro-3, 6-dioxa-4-methyl-7-octene benzenesulfonyl imide, has been synthesized from Nafion monomer for the first time. With trifluorovinyl ether and diazonium precursors, the partially-fluorinated diazonium PFSI monomer can be polymerized and will provide chemically bonding with carbon electrode in proton exchange membrane fuel cells. A systematic study of the synthesis and characterization of this diazonium PFSI monomer has been conducted by varying reaction conditions. The optimized synthesis method has been established in the lab.

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Solar Energy and Hydrogen (energy carrier) are possible replacement options for fossil fuel and its associated problems of availability and high prices which are devastating small, developing, oil-importing economies. But a major drawback to the full implementation of solar energy, in particular photovoltaic (PV), is the lowering of conversion efficiency of PV cells due to elevated cell temperatures while in operation. Also, hydrogen as an energy carrier must be produced in gaseous or liquid form before it can be used as fuel; but its‟ present major conversion process produces an abundance of carbon dioxide which is harming the environment through global warming. In search of resolutions to these issues, this research investigated the application of Thermal Management to Photovoltaic (PV) modules in an attempt to reverse the effects of elevated cell temperature. The investigation also examined the effects of coupling the thermally managed PV modules to a proton exchange membrane (PEM) Hydrogen Generator for the production of hydrogen gas in an environmentally friendly and renewable way. The research took place in Kingston, Jamaica. The thermal management involved the application of two cooling systems which are Gravity-Fed Cooling (GFC) and Solar-Powered Adsorption Cooling (SPAC) systems. In both systems Mathematical Models were developed as predictive tools for critical aspects of the systems. The models were validated by the results of experiments. The results of the investigation showed that both cooling systems stopped the cells temperatures from rising, reversed the negative effects on conversion efficiency, and increased the power output of the module by as much as 39%. The results also showed that the thermally managed PV module when coupled to the hydrogen generator impacted positively with an appreciably increase of up to 32% in hydrogen gas production. The results of this work can be applied to the equatorial belt but also to other regions with suitable solar irradiation. The research has contributed to the wider community by the development of practical, environmentally friendly, cost effective Thermal Management Systems that guarantee improvement in photovoltaic power output, by introducing a novel way to use renewable energy that has potential to be used by individual household and/or as cottage industry, and by the development of Mathematical Tools to aid in photovoltaic power systems designs.

The overall goal of this research is to synthesize two different monomers for proton exchange membrane (PEM) Fuel Cells. Such monomers are proposed to be polymerized to improve the efficiency and compatibility of electrodes and electrolytes in PEM fuel cells. The first target is to synthesize 4-diazonium-3-fluoro PFSI zwitterionic monomer. Three steps were carried out in the lab. First one was the ammonolysis of 3-fluoro-4-nitrobenzenesulfonyl chloride. Second reaction was the bromination of Nafion monomer. The next coupling reaction, between brominated Nafion monomer and the 3-fluoro-4-nitrobenzenesulfonamide, was failed. The obstacles involve the harsh reaction condition and troublesome purification procedure. The second target is to synthesize 5-nitro-1, 3-benzenedisulfonamide. According to the literature, this synthesis was also designed as three steps: 1)nitration of sodium 1, 3-benzenedisulfonate salt; 2)chlorination of sodium 5-nitro-1, 3-benzenedisulfonate salt; and 3)ammonolysis of 5- nitro-1, 3- benzenedisulfonyl chloride. This monomer is expected to be copolymerized for membrane electrolyte in PEM fuel cells.

Intensive research on development of alternative low cost, high temperature membranes for proton exchange membrane (PEM) fuel cells is going on because of the well-known limitations of industry standard perfluoro-sulfonic acid (PFSA) membranes. To overcome these limitations such as the decrease in performance at high temperatures (&gt / 80 0C) and high cost, non-fluorinated aromatic hydrocarbon based polymers are attractive. The objective of this study is to develop alternative membranes that possess comparable properties with PFSA membranes at a lower cost. For this purpose post-sulfonation studies of commercially available engineering thermoplastics, polyether-ether ketone (PEEK) and polyether-sulfone (PES), were performed by using suitable sulfonating agents and conditions. Post sulfonated polymers were characterized with proton nuclear magnetic resonance spectroscopy (H+-NMR), sulfur elemental analysis and titration to calculate the degree of sulfonation (DS) values and with TGA and DSC for thermal stability and glass transition temperature (Tg). Chemical stabilities were evaluated by hydrogen v peroxide tests. Proton conductivities of sulfonated PEEK (SPEEK) measured by electrochemical impedance spectroscopy (EIS) were observed to increase linearly with degree of sulfonation (DS). However, above a certain DS SPEEK loses its mechanical stability significantly with excessive swelling which leads to deteriorations in mechanical stability. Therefore, DS of 50-70% were used for the fabrication of composite membranes. To improve mechanical stability, SPEEK polymers were blended with more stable polymers, polyether-sulfone (PES) or in its sulfonated form (SPES) or with polybenzimidazole (PBI). In addition, the composite approach, which involves the incorporation of various inorganic fillers such as zeolite beta, TiO2, montmorrilonite (MMT), heteropolyacids (HPA), was used for further improvement of proton conductivity. Among the composite membranes 20% TPA/SPEEK (DS=68) composites conductivity value exceeded that of Nafion&lsquo / s at room temperature. Effects of various parameters during the fabrication process such as the filler type and loading, DS of sulfonated polymer, casting solvents, and thermal and chemical treatment were also investigated and optimized. Various blend/composite membranes were fabricated with solvent casting method, and characterized for their proton conductivity, chemical/thermal stability and for evaluating their voltage/current performance at various temperatures in a single cell setup. Chemically and thermo-hydrolytically stable composite/blend membranes such as 25% tungstophosphoric acid (TPA)/PBI(5%)/SPEEK (DS=68) with good single cell performances at 800C were developed (~450 mA/cm2 at 0.5 V). The performance of the hydrolytically stable composite/blend membrane prepared with SPEEK (DS=59) / 5% PBI / and 10% TiO2 increased appreciably when the temperature was raised from 80 0C to 90 0C while the performance of Nafion decreases sharply after 80 0C. Methanol permeability studies were also performed for investigating the potential of fabricated blend/composite membranes for direct methanol fuel cell (DMFC) use. Selectivities (conductivity/methanol permeability) vi greater than Nafion 112 (S=7.3x107) for DMFC were observed for composite/blend membranes such as 10% TiO2/10% PES blend with SPEEK (DS=68) with a selectivity of 9.3x107. The factors that affect proton conductivity measurements were investigated and equivalent circuit analysis was performed with results obtained by electrochemical impedance spectroscopy (EIS). The choice of the conductivity cell (electrodes, cell geometry) and the method (2-probe vs 4-probe) were shown to affect the conductivity analysis. A systematic development and characterization route was established and it was shown that by optimizing proton conductivity and thermal/chemical stability with blending/composite approaches it is possible to produce novel high performance proton exchange membranes for fuel cell applications.

Two diazonium perfluoroalkyl arylsulfonimide (PFSI) zwitterionic monomers, 4-diazonium perfluoro(3-oxapent-4-ene)benzenesulfonimide (I) and 4-(trifluoromethyl)-2-diazonium perfluoro(3-oxapent-4-ene)benzenesulfonimide (II) have been synthesized from perfluoro(3-oxapent-4-ene) sulfonyl fluoride (POPF) for proton exchange membrane fuel cells. PFSI polymers are proposed as new electrolytes due to their better thermal stability, inertness to electrochemical conditions, and lower susceptibility to oxidative degradation and dehydration. For a better integration between the electrode and the electrolyte, the PFSI polymers are expected to be grafted onto the carbon electrode via the diazonium moiety. All the reaction intermediates and the final product were characterized with 1H NMR, 19F NMR and IR spectroscopies.

In order to keep the Paris Agreement's goal of limiting global warming to well below 2°C, greenhouse gas emissions should be reduced. However, larger measures need to be implemented as it has been established that today's measures will not be enough. The Port of Gävle has plans to install a water electrolyser for hydrogen production of either Proton Exchange Membrane (PEM) or Alkaline Water Electrolysis(AWE). The size of the electrolyser will be approximately 10 MW and will have the capacity to produce 2,000 tons of fossil-free hydrogen per year that might supply 100 heavy trucks. However, it is currently cheaper with fossil hydrogen production. Therefore, an article review is conducted containing a calculation part where the purpose is to investigate the amount of by-products produced and whether they can be sold in other areas of use to make renewable hydrogen more economically competitive. Information for the study has been retrieved from databases, search engines, companies, authorities and individuals deemed relevant to the study. The by-products from the 10 MW electrolyser in the Port of Gävle have been compared with 1,5 MW and 17 MW electrolysers, then a sensitivity analysis has also beenperformed on the 10 MW electrolysers. The potentially generated heat depends on the type of electrolyser where AWE generates 77 MWh of residual heat per day and PEM potentially generates 67 MWh of residual heat per day. Furthermore, AWE needs 64 kWh of electricity to produce 1 kg of hydrogen while PEM needs 66,5 kWh of electricity per kg of hydrogen produced. Revenues from residual heat sales for AWE were estimated annually to approximately 7 million SEK and for PEM approximately 6 million SEK. For electrolysis-produced oxygen to compete with cryogenic oxygen, the price should not exceed 108 SEK/tonne. For the 10 MW electrolyser, oxygen sales are estimated to generate approximately 1,1 million SEK annually for both AWE and PEM. Total income for AWE will annually be just over 8,1 million SEK and 7.1million SEK annually for PEM. The AWE process is then preferable as it is more economically sustainable as the income from the by-products is 12% higher than PEM due to higher production of oxygen and greater generation of residual heat. / För att hålla Parisavtalets mål att begränsa den globala uppvärmningen till väl under 2°C bör utsläppen av växthusgaser minska. Däremot behöver större åtgärder genomföras då det har konstaterats att dagens åtgärder inte kommer att räcka. Gävle hamn har planer på att installera en vattenelektrolysör för vätgasproduktion av antingen Protonutbytesmembran (PEM) eller Alkalisk vattenelektrolys (AWE). Storleken på elektrolysören kommer vara ungefär 10 MW och har kapaciteten att producera 2000 ton fossilfri vätgas per år som kan försörja 100 tunga lastbilar. Dock är det i dagsläget billigare med fossil vätgasproduktion. Därför genomförs en litteraturstudie innehållande en beräkningsdel. Där syftet är att undersöka mängden biprodukter som produceras samt om de kan säljas inom andra områden för att göra förnyelsebar vätgas mer ekonomiskt konkurrenskraftig. Information för studien har hämtats från databaser, sökmotorer, företag, myndigheter och enskilda personer som ansetts relevanta för studien. Biprodukterna från 10 MW elektrolysören i Gävle hamn har jämförts med 1,5 MW och 17 MW elektrolysörer, sedan har även en känslighetsanalys utförts på elektrolysörerna. Potentialen att generera värme beror på typen av elektrolysör där AWE genererar 77 MWh restvärme per dygn och PEM genererar potentiellt 67 MWh restvärme per dygn. Vidare behöver AWE 64 kWh el för att producera 1 kg vätgas medan PEM behöver 66,5 kWh el per producerat kg vätgas. Intäkterna från restvärmeförsäljningen för AWE beräknades årligen till ungefär 7mnSEK och för PEM ungefär 6 mnSEK. För att elektrolysframställd syrgas ska kunna konkurrera med kryogent framställd syrgas bör inte priset övergå 108 SEK/ton. För 10 MW elektrolysören beräknas syrgasförsäljningen kunna inbringa omkring 1,1 mnSEK årligen både för AWE och PEM. Totala inkomsten för AWE blir drygt 8,1 mnSEK/år och 7,1 mnSEK/år för PEM. AWE processen är att föredra då den är mer ekonomiskt hållbar då inkomsten från biprodukterna är 12% högre än PEM på grund av högre produktion av syrgas samt större generering av restvärme.

Le développement de catalyseurs de la réaction de dégagement de l’oxygène (OER) pour les électrolyseurs à membrane échangeuse de protons (PEM) dépend de la compréhension du mécanisme de cette réaction. Cette thèse est consacrée à l'application de la spectroscopie d’émission de photoélectrons induits par rayons X (XPS) et de la spectroscopie de structure près du front d'absorption de rayons X (NEXAFS) operando sous une pression proche de l'ambiante (NAP) dans le but d’étudier les mécanismes de la réaction d’oxydation de l’eau sur des anodes à base d’iridium et de ruthénium et leurs dégradation dans les conditions de la réaction. Cette thèse montre les mécanismes différents de la réaction OER pour les anodes à base d’Ir et de Ru impliquant respectivement des transitions anioniques (formation d’espèce OI- électrophile) ou cationiques (formation des espèces de Ru avec l’état d'oxydation supérieur à IV) quelle que soit la nature (thermique ou électrochimique) des oxydes. / Development of oxygen evolution reaction (OER) catalysts for proton exchange membrane water electrolysis technology depends on the understanding of the OER mechanism. This thesis is devoted to the application of near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and near edge X-ray absorption fine structure (NEXAFS) techniques for operando investigation of the Ir, Ru - based anodes. For Ru-based systems, we observe the potential-induced irreversible transition of Ru (IV) from an anhydrous to a hydrated form, while the former is stabilized in the presence of Ir. Regarding single Ir-based anodes, the analysis of O K edge spectra reveals formation of electrophilic oxygen OI- as an OER intermediate. Higher stability of Ir catalysts supported on antimony-doped tin oxide (ATO) is related to their lower oxidation. This work demonstrates different OER mechanisms on Ir, Ru-based anodes involving anion and cation red-ox chemistry, correspondingly, regardless the oxide nature.