Carbon monoxide (CO) is a colourless and highly toxic gas. The detection of CO is a key requirement for safety and control in combustion processes. A number of sensors are currently available but all have drawbacks with most if not all having questions raised about their effective detection of CO over other gases such as hydrogen and methane. The power consumption of some methods of gas sensing is high as the active material must be heated to 400.600°C in order to function. The aim of this project was to attempt to eliminate this high power requirement and to study the design, fabrication and testing of CO sensors which function at room temperature, based on a supported platinum electrode in combination with a solid polymer electrolyte. It is therefore conceivable that the power source of such a sensor could be a battery, which could power a microcontroller and the relatively simple diagnostic testing equipment in a final commercial product.

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The purpose of this thesis was to carry out the experimental study of direct ammonia fuel cells. The use of hydrogen in fuel cells poses a lot of problems. There is a lot of safety, technical and economic issues to be overcome to make its use as a fuel widespread. Ammonia is being considered as a very promising source of hydrogen for fuel cells. However, until now its use in fuel cells has received very little attention. Ammonia presents many advantages over hydrogen and other potential sources of hydrogen such as an easy storage and a world-wide distribution network. Ammonia is a suitable hydrogen carrier and can be easily cracked at high temperatures such as those used in solid oxide fuel cells. The present study was conducting using ammonia as fuel and argon as carrier gas in different solid oxide fuel cell systems: an annular design, a planar design and a micro laminated reactor. The electrolyte materials were calcia stabilized zirconia and yttria stabilized zirconia. As far as the electrodes are concerned, silver, platinum and nickel cermet were used as anode/materials and silver was employed as cathode material. The cell yoltage was measured as function of reactor configuration, space time, ammonia flow rate and ammonia concentration. The results demonstrate the high potential of ammonia over hydrogen when nickel is used as anode material. Solid proton conducting fuel cells operating on ammonia fuel were also studied. The electrolyte materials were fabricated from neodymium and gadolinium doped barium and strontium cerates. The dopant fraction ranged from 1 to 20 wt%. Silver was employed as cathode and anode material and was spray deposited. The application of proton conducting electrolytes results in higher current densities for a given voltage than the using typical oxide ion conductors such as 8mol % yttria stabilized zirconia. The potential of the proton conducting materials for application in ammonia synthesis at atmospheric pressure was also studied. They demonstrated promising results and could prove to be an alternative to the common ammonia synthesis processes.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22706号 / 工博第4753号 / 新制||工||1743(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 江口 浩一, 教授 陰山 洋, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Proton conducting intermediate temperature (600oC-400oC) solid oxide fuel cells (IT-SOFC) have many potential advantages for clean and efficient power generation from readily available hydrocarbon fuels. However, it still has many unsolved problems, especially on the anode where the fuel got oxidized and the cathode where oxygen got reduced. In this study, for the anode, the effects of hydrogen sulfite (H2S) and carbon dioxide (CO2) as fuel contaminants were studied on the nickel (Ni) based cermet anode of proton conducting IT-SOFC using proton conducting electrolyte of BaZr0.1Ce0.7Y0.1Yb0.1O3 (BZCYYb). Both low-ppm level H2S and low-percentage level CO2 caused similar poisoning effects on the anode reaction. The H2S poisoning effect was also found to be much less than on oxide-ion conducting SOFC, which is attributed to the absence of water evolution for the anode reaction in proton conducting SOFC. In addition, the H2S/CO2 poisoning mechanisms were investigated using X-ray diffraction, energy dispersive spectroscopy (EDS), Raman spectroscopy, and secondary ion mass spectroscopy (SIMS). For H2S, other than possible sulfur dissolution into BZCYYb, no bulk reaction was found, suggesting sulfur adsorption contributes to the reduced performance. For CO2, reaction with BZCYYb to form BaCO3 and CeO2 is identified and is believed to be the reason for the sudden worsening in CO2 poisoning as temperature drops below ~550oC. For the cathode, several representative SOFC cathodes including silver (Ag), La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), LSCF-BZCYYb composite, and Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) were evaluated based on BZCYYb electrolyte. LSCF give similar high interfacial resistance as Ag, while LSCF-BZCYYb composite cathode shows lower interfacial resistance, suggesting LSCF behaves like pure electronic conductor cathode in this case. For BSCF, it shows smallest interfacial resistance and the charge transfer process appears to accelerate with the introduction of H2O, while oxygen adsorption/transport seem to slow down due to adsorbed H2O. Furthermore, CO2 was shown to cause poisoning on the BSCF cathode, yet the poisoning was significantly reduced with the co-presence of water. The results suggest that although BSCF seem to display mixed proton-electronic conduction, its strong affinity to H2O may inhibit the oxygen reduction reaction on the cathode and new cathode materials still need to be designed.

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The objective of the research described in this thesis has been to improve the toughness of phenolic networks while maintaining flame resistance. A four step synthetic scheme has been developed to prepare 4,4′-Bis(3,4-dicyanophenoxy)biphenyl(biphenoxyphthalonitrile). A 700 g mol-1 novolac oligomer was cured with relatively low concentrations of this reagent (~20 wt %) into high Tg (~190 °C) networks. The curing reaction was attrubuted to nucleophilic attack of the phenolic hydroxyl on the nitrile groups of the phthalonitrile resulting in the formation of heterocylic rings. TGA and cone calorimetry demonstrated that these networks have excellent thermo-oxidative stability. Further goals were to develop halogen-free, flame retardant monomers for improving the thermo-oxidative resistance of polystyrene and dimethylacrlyate/styrene(vinyl ester) networks. 4-Vinylphenoxyphthalonitrile, a phthalonitrile derivative of styrene, was synthesized. FTIR has been utilized to demonstrate this new monomer co-cured into vinyl ester networks in free radical thermosetting polymerizations. Upon post-curing the networks between 200-260 °C for ~1.5 h, the nitrile groups reacted to form heterocyclic crosslinks. TGA and cone calorimetry demonstrated that the 4-vinylphenoxyphthalonitrile substantially improved the flame resistance of vinyl ester networks. Copolymerizations of styrene and 4-vinylphenoxyphthalonitrile were conducted at 75 °C for 24 h using 0.5 wt % AIBN in chlorobenzene. Dynamic TGA at 10 °C min-1 in air showed that copolymers containing 10 and 25 mole % of 4-vinylphenoxyphthalonitrile had increased initial weight loss temperatures in air by (~50 °C higher) and increased the char yield between 400-600 °C. High molecular weight nitrile-functional, (hexafluoroisopropylidene)diphenol based aromatic poly(arylene ether)s with pendent sulfonic acid groups were prepared by nucleophilic step copolymerization of 4,4′-(hexafluoroisopropylidene)diphenol, 2,6-dichlorobenzonitrile, and 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone under basic conditions in N-methyl-2-pyrrolidinone at 200 °C. A series of these materials with systematically varied concentrations of the sulfonic acid moieties showed increased glass transition temperatures, proton conductivities, and hydrophilicities as a function of disulfonation. Atomic force microscopy (AFM) demonstrated that the acidified copolymer with 35 mole % of disulfonated units was phase separated into a co-continuous morphology of hydrophobic and hydrophilic domains. / Ph. D.

Proton exchange membrane fuels cells (PEMFCs) are one of the primary alternatives to internal combustion engines. The key component is the proton exchange membrane, or PEM, which should meet a number of requirements, including good proton conductivity under partially humidified conditions. A number of alternative PEMs have been synthesized by copolymerizing various aromatic comonomers, but the smaller ion channels prohibit rapid proton transport under partially hydrated conditions. One solution has been to synthesize multiblock copolymers from hydrophilic and hydrophobic oligomers to ensure sufficient ion channel size. Four multiblock systems were synthesized from hydrophobic and hydrophilic oligomers and were characterized in this thesis. The first multiblock system incorporated a partially fluorinated monomer into the hydrophobic block, to improve phase separation and performance under partially humidified conditions. The second study was focused on phase separation and structure-property relationships as a function of casting conditions of a biphenol-based multiblock series. The third study featured a novel hydroquinone-based hydrophilic oligomer in the multiblock copolymer, which showed the promise of a higher ionic density, degree of phase separation and proton conductivity values. The fourth study in this thesis entailed the comparison of a block copolymer produced with two distinct synthetic routes: the multiblock synthesis from separate oligomers as previously published in the literature, and a segmented route seeking to achieve comparable structure-property relationships with the same monomers, but using a simpler synthetic route. The two block copolymer series were found to be comparable in their structure-property relationships. / Master of Science

Conducting polymers entered the research field in late 70´s and efforts aimed at achieving printed electronics started a decade later. This thesis treats printable organic electrochemical transistors (OECT). Some conjugated polymers can be switched between a high conducting and a low conducting state in an electrochemical cell. In this thesis, the work carried out using poly(3,4-ethylenedioxythiophene) (PEDOT) as the active material in an electrochemical transistor is reported. The electrochemical transistors, presented, can be designed into a bi-stable and dynamic mode of operation. These transistors operates at voltages below 2V and current on/off ratios are typically 5000, but 105 have been reached. The transistor device can be built up from all-organic materials using common printing techniques such as with screen-printing. The bi-stable transistor can be combined with an electrochromic (EC) display cell to form a smart pixel circuit. Combining several of these smart pixels yield an actively addressed cross-point matrix display. From this an all-organic active matrix display printable on paper has been achieved. The OECT, combined with a resistor network was successfully used in inverter and logic circuits. One important feature of these organic electrochemical devices is that both ions and electrons are used as the charge (signal) carriers. This is of particular interest and importance for chemical sensors. By combining a proton-conducting electrolyte (Nafion®) that changes its conductivity upon exposure to humidity, a simple OECT humidity sensor was achieved. This proves the use of this OECT as the ion-to-electron transducer.