Due to the petroleum crisis and its consequent emission problems, fuel cells gain an important place in the application of alternative energy. They are a kind of electrochemical device that converts chemical energy directly into electrical energy. The Direct Methanol Fuel Cells (DMFC) use polymer membranes as the electrolyte; the polymer membranes are capable of conducting hydrogen protons. The fuel cell system is still expensive and the proton exchange membrane has contributed significantly the high cost. At present, perfluorosulfonic acid membranes (PFSA) (e.g. Nafion®, by DuPont) have been widely investigated. However they showed high methanol crossover and high swelling that lead low cell efficiency. The main goal of the thesis is to prepare novel proton exchange membranes to apply in the DMFC. PEG and PA membranes compuestas fueron preparadas. Derivados del ácido fosfórico y lignosulfonados (LS) fueron incluidos en la estructura de la PA para actuar como agentes transportadores de protones. El mecanismo de la conductividad de protón es "hopping". Ellos mostraron el más baja del transporte de metanol.Se obtuvieron también membranas híbridas de LS, preparadas mediante la mezcla de los dos polímeros, LS y PSU, siguiendo el método de precipitación en inmersión. Las propiedades electroquímicas de las membranas de LS fueron caracterizadas. Las membranas de LS alcanzaron conductividades de protón aceptables (10-20 mS/cm) con capacidad de intercambio iónico muy baja (IEC) (60 veces más baja que Nafion). "Membrane electrode assemblies" (MEAs) fueron preparadas y sus rendimientos de celda fueron medidos en una celda individual directa de metanol (DMFC). LS membrana is the highlight point of this thesis. It demonstrated the first that LS is a good proton exchange material although it is a waste from the paper industry. It also proved that porous membrane can be used in the DMFC with acceptable proton conductivity and low methanol permeability, which is a totally new way from the existing literatures.The results have been published on international journals and have been presented on international conferences:1. X. Zhang, A. Glüsen, R. Garcia-Valls, Porous Lignosulfonate membrane for direct methanol fuel cells, accepted by Journal of Membrane Science, 20052. X. Zhang, J. Benavente, R. Garcia Valls, Lignin-based Membranes for Electrolyte Transference, Journal of Power Sources, 145 (2005) 2923. X. Zhang, L. Pitol Filho, C. Torras, R. Garcia Valls, Experimental and Computational Study of Proton and Methanol Permeability through Composite Membranes, Journal of Power Sources, 145 (2005) 2234. J. Benavente, X. Zhang, R. Garcia Valls, Modification of Polysulfone Membranes with Polyethylene Glycol and Lignosulfate: Electrical Characterization by Impedance Spectroscopy Measurements, Journal of Colloid and Interface Science, 285 (2005) 273-2805. X. Zhang, R. Garcia-Valls, Proton transport membrane containing lignin compound for direct methanol fuel cells (Poster), 5th Ibero American Congress on Membrane Science and Technology, 2005, Valencia- Spain 6. X. Zhang, J. Benavente and R. Garcia-Valls, Lignin-based membranes for electrolyte transference (Oral presentation), Fuel Cell Science & Technology, Oct. 2004, Munich- Germany. 7. X. Zhang, R. Garcia-Valls, New membranes for Proton Transport in DMFC (Poster), Euromembrane Sep. 2004, ISBN: 3-930400-65-0, p. 64, Hamburg- Germany, 8. X. Zhang, R. Garcia-Valls, Lignosulfonate Application in Proton Transport Membrane (Oral presentation), 2nd World Conference and Technology Exhibition on Biomass for Energy, Industry and Climate Protection, May. 2004, Rome- Italy9. X. Zhang, R. Garcia-Valls, Proton Selective Composite Membrane for Direct Methanol Fuel Cell (Oral presentation), 5th NYM (Network Young Membrains) Oct. 2003, ISBN: 84-688-3132-8, p. 199, Barcelona, Spain10. X. Zhang, R. Garcia-Valls, A. Jiménez-López, E. Rodríguez-Castellón and J. Benavente, Electrical and Chemical Surface Characterization of Lignosulfate/Polysulfone Membranes for Fuel Cells Application, International Conference on "New Proton Conducting Membranes and Electrodes for PEM FCs", Oct. 2005, Assisi, Italy. / Debido a la crisis de petróleo y a los problemas de emisión, las pilas de combustible adquieren un lugar importante en la aplicación de la energía alternativa. Son una clase de dispositivo electroquímico que convierte la energía química directamente en energía eléctrica. Las celdas de combustible de metanol (DMFC) usan membranas de polímero como el electrolito; las membranas de polímero son capaces de transportar protones de hidrógeno. El sistema de la celda de combustible todavía es costoso y las membranas de intercambio de protón han contribuido significativamente para el costo elevado.Actualmente, las membranas de ácido perfluorosulfonico (PFSA) (por ejemplo, Nafion ®, de DuPont) ten sido investigadas extensamente. Sin embargo mostraron alto paso de metanol e alto "swelling" lo que lleva a una eficiencia de celda baja.El objetivo principal de la tesis es preparar membranas de intercambio de protón nuevas para la aplicación en DMFC. Membranas compuestas de PEG y de PA fueron preparadas. Derivados del ácido fosfórico y lignosulfonados (LS) fueron incluidos en la estructura de la PA para actuar como agentes transportadores de protones. El mecanismo de conductividad de protón es "hopping". Ellos mostraron el transporte de metanol más bajo.Se obtuvieron también membranas híbridas de LS, preparadas mediante la mezcla de los dos polímeros, LS y PSU, siguiendo el método de precipitación en inmersión. Las propiedades electroquímicas de las membranas de LS fueron determinadas. Las membranas de LS alcanzaron conductividades de protón aceptables (10-20 mS/cm) con capacidad de intercambio iónico muy baja (IEC) (60 veces más baja que Nafion). "Membrane electrode assemblies" (MEAs) fueron preparadas y sus rendimientos de celda fueron medidos en una celda individual directa de metanol (DMFC).Las membranas de LS son el punto principal de esta tesis. Primero se demostró que LS es un material de intercambio de protón muy bueno aunque sea un residuo de la industria de papel. También se probó que membranas porosas pueden ser usadas en DMFC con una conductancia de protón aceptable y baja permeabilidad de metanol, lo que es una manera totalmente nueva comparada a la literatura existente.Los resultados han sido divulgados en revistas internacionales y han sido presentados en conferencias internacionales:1. X. Zhang, A. Glüsen, R. Garcia-Valls, Porous Lignosulfonate membrane for direct methanol fuel cells, accepted by Journal of Membrane Science, 20052. X. Zhang, J. Benavente, R. Garcia Valls, Lignin-based Membranes for Electrolyte Transference, Journal of Power Sources, 145 (2005) 2923. X. Zhang, L. Pitol Filho, C. Torras, R. Garcia Valls, Experimental and Computational Study of Proton and Methanol Permeability through Composite Membranes, Journal of Power Sources, 145 (2005) 2234. J. Benavente, X. Zhang, R. Garcia Valls, Modification of Polysulfone Membranes with Polyethylene Glycol and Lignosulfate: Electrical Characterization by Impedance Spectroscopy Measurements, Journal of Colloid and Interface Science, 285 (2005) 273-2805. X. Zhang, R. Garcia-Valls, Proton transport membrane containing lignin compound for direct methanol fuel cells (Poster), 5th Ibero American Congress on Membrane Science and Technology, 2005, Valencia- Spain6. X. Zhang, J. Benavente and R. Garcia-Valls, Lignin-based membranes for electrolyte transference (Oral presentation), Fuel Cell Science & Technology, Oct. 2004, Munich- Germany.7. X. Zhang, R. Garcia-Valls, New membranes for Proton Transport in DMFC (Poster), Euromembrane Sep. 2004, ISBN: 3-930400-65-0, p. 64, Hamburg- Germany,8. X. Zhang, R. Garcia-Valls, Lignosulfonate Application in Proton Transport Membrane (Oral presentation), 2nd World Conference and Technology Exhibition on Biomass for Energy, Industry and Climate Protection, May. 2004, Rome- Italy9. X. Zhang, R. Garcia-Valls, Proton Selective Composite Membrane for Direct Methanol Fuel Cell (Oral presentation), 5th NYM (Network Young Membrains) Oct. 2003, ISBN: 84-688-3132-8, p. 199, Barcelona, Spain10. X. Zhang, R. Garcia-Valls, A. Jiménez-López, E. Rodríguez-Castellón and J. Benavente, Electrical and Chemical Surface Characterization of Lignosulfate/Polysulfone Membranes for Fuel Cells Application, International Conference on "New Proton Conducting Membranes and Electrodes for PEM FCs", Oct. 2005, Assisi, Italy La tesis tuvo la cooperación del Forschungszentrum Jülich, Alemania y la doctoranda esta solicitando el titulo de Doctorado Europeo.

Polymer electrolyte membrane fuel cells (PEMFCs) exhibit encouraging potential as an enabling technology for the Hydrogen Economy. Currently an important barrier to commercialization is the cost associated with existing PEMFC materials; this project’s goal was to investigate alternative materials for PEMFC bipolar plates. Conductive thermoplastic materials offer the promise of low density, low cost processing, and inexpensive resins, and were the focus of material development for PEMFC bipolar plate applications. In order to develop a thermoplastic bipolar plate this study utilized the combination of a low cost injection moldable commodity polymer resin, and low cost carbon materials as conductive fillers. The materials selected and tested included; a polypropylene copolymer; acetylene carbon black; Vulcan carbon black; and short carbon fiber. The components were combined in a twin screw extruder and injection molded into samples for testing. The result was a spectrum of composite samples with a range of filler loadings from 0 to 60 wt% and varying filler type ratios. Synergy between the different carbon types was achieved which led to better physical properties, specifically conductivity. The novel blends produced were tested for electrical conductivity, mechanical properties, rheology, microscopy, and actual plates were made and tested in a single cell PEMFC. These trials enabled discussion around the feasibility of the materials with respect to processability, cost, and performance (both in the fuel cell and in potential applications). The most significant results were measured using a composite blend with 54 wt% filler loading and a 1:1:1 filler ratio. Mechanical results achieved 68% and 100% of the industry targets for tensile and flexural strength, respectively. Tensile strength attained 27.7 MPa and flexural strength measured 82.8 MPa. Electrical conductivity results for the same samples varied between the two methods of measurement used. Using a fuel cell industry recommended procedure 2.2 S/cm was achieved and using a four point ASTM measurement technique 12.0 S/cm was reported. These values represent 3% to 12% of the industry target. Actual 16 cm2 fuel cell plates were produced, fuel cell hardware constructed and assembled, and the power output was found to be 51% relative to graphite plates. Thermoplastic bipolar plates for PEMFCs made of composite materials is promising, but optimum filler loading that balances all properties is still required in order to achieve conductivity targets. Nevertheless this study has demonstrated that conductive thermoplastic bipolar plates can be produced via injection molding.

Reducing fabrication and operation costs while maintaining high performance is a major consideration for the design of a new generation of solid-state ionic devices such as fuel cells, batteries, and sensors. The objective of this research is to fabricate nanostructured materials for energy storage and conversion, particularly porous electrodes with nanostructured features for solid oxide fuel cells (SOFCs) and high surface area films for gas sensing using a combustion CVD process. This research started with the evaluation of the most important deposition parameters: deposition temperature, deposition time, precursor concentration, and substrate. With the optimum deposition parameters, highly porous and nanostructured electrodes for low-temperature SOFCs have been then fabricated. Further, nanostructured and functionally graded La0.8Sr0.2MnO2-La0.8SrCoO3-Gd0.1Ce0.9O2 composite cathodes were fabricated on YSZ electrolyte supports. Extremely low interfacial polarization resistances (i.e. 0.43 Wcm2 at 700¡ãC) and high power densities (i.e. 481 mW/cm2 at 800¡ãC) were generated at operating temperature range of 600¡ãC-850¡ãC. The original combustion CVD process is modified to directly employ solid ceramic powder instead of clear solution for fabrication of porous electrodes for solid oxide fuel cells. Solid particles of SOFC electrode materials suspended in an organic solvent were burned in a combustion flame, depositing a porous cathode on an anode supported electrolyte. Combustion CVD was also employed to fabricate highly porous and nanostructured SnO2 thin film gas sensors with Pt interdigitated electrodes. The as-prepared SnO2 gas sensors were tested for ethanol vapor sensing behavior in the temperature range of 200-500¡ãC and showed excellent sensitivity, selectivity, and speed of response. Moreover, several novel nanostructures were synthesized using a combustion CVD process, including SnO2 nanotubes with square-shaped or rectangular cross sections, well-aligned ZnO nanorods, and two-dimensional ZnO flakes. Solid-state gas sensors based on single piece of these nanostructures demonstrated superior gas sensing performances. These size-tunable nanostructures could be the building blocks of or a template for fabrication of functional devices. In summary, this research has developed new ways for fabrication of high-performance solid-state ionic devices and has helped generating fundamental understanding of the correlation between processing conditions, microstructure, and properties of the synthesized structures.

Planar solid oxide fuel cells (SOFCs) were designed, fabricated and characterized in order to develop a (1) cost-effective method for fabrication of thin electrolyte layers, (2) hermetic sealing and (3) stable interconnects. Electrophoretic deposition (EPD) was discovered to be an excellent method for fabricating dense electrolyte layers of about 5m thick on porous non-conducting substrates. The EPD process was thoroughly studied from proof-of-concept to statistical reproducibility, deposition mechanism, modeling and process optimization. Deposition on non-conducting substrates was found to follow many of the same fundamental trends as that on conductive substrates except for the voltage efficiency and detailed charge transfer mechanism. Eventually, the process was optimized such that an SOFC was fabricated that achieved 1.1W/cm2 at 850C. Further, a novel sealless planar SOFC was designed that incorporates a hermetic interface between the electrolyte and interconnect similar to tubular and honeycomb designs. The hermetic interface successfully acted as a blocking electrode under DC polarization, indicating its potential to act as a sealant. Leakage rates across the interface were 0.027sccm at 750c, similar to polycrystalline mica seals. Through a process of tape casting and lamination, a two-cell stack without sealant was fabricated and achieved a power density of 75mW/cm2 at 750C. Finally, the degradation rate of silver and silver-based interconnects was studied under static and dual-atmosphere conditions. Corrosion of silver grain boundaries along with sublimation losses results in the formation of large pores, resulting in up to 30 of anode oxidation after 8hrs testing at 750c. Further stability studies indicated that silver-based interconnects would be better suited for applications at operating temperatures less than 650C.

The green house effect caused by the emission of carbon dioxide has adverse impact on the ecosystem of the earth. The traditional fossil power plants generate this green house effect by their tremendous amount of carbon dioxide during operation. On the other hand, for the traditional long distance power transmission that needs not only large amount land and capital investments but also is easy to be interrupted due to severe climate, which causes the minimize the reliability of the power supply. Moreover, it would affect national economic development and the quality of life. In this respect, the demand for the power produced from small clean power systems has significantly increased. In those clean power systems, fuel cells power industry becomes a burgeoning and promising industry. A fuel cell is an electrochemical energy conversion device that converts hydrogen and oxygen into water, producing electricity and heat in the process. It stands out of many alternative power sources for its high efficiency, low pollution, and capability of reducing green house effect and becomes a focus of global energy market. However, its higher cost leads to less competitive than the traditional power sources. According to the experience of advanced countries, at this starting stage, it has to rely on the policy support and financial subsidy of the governments to attract the early adoption. In addition, the long-term support to the technological development can help the cost reduction and the achievement of full commercialization level. The main purpose of this study is to discuss the feasibility of Taiwan¡¦s developing fuel cells power system. According to Taiwan¡¦s status, Taiwan Power Company (Taipower) plays an important role to develop the fuel cells power, so a 4P marketing strategy under the standpoint of Taipower including Product, Price, Promotion, and Path strategy has been presented. Finally, recommendations of developing fuel cells to Taiwan government are also included in this study.

The efficiency of the fuel cell depends on both the kinetics of the electrochemical process and performance of the components. The main aim of this research is to analysis the reliability of the cracked Ag-SU8 interface on the channel wall in a micro-PEMFC. An existed surface crack on the channel wall subjected to the flow induced compressive stresses and shear stresses will propagate and lead to the spall formation. The results show that as the crack length increases, the value of KI will increase, but the value of KII decreases slightly. The reliability analysis of the interfacial crack between Ag and SU8 on the Micro-channel wall in PEMFC is discussed in this thesis.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 127-134).

Thesis (M.S.)--Engineering, Georgia Institute of Technology, 2004. / McDowell, David, Committee Chair; Neu, Richard, Committee Member; Lee, Jim, Committee Member; Cochran, Joe, Committee Member. Includes bibliographical references (leaves 159-162).

Includes bibliographical references (p. 181-194).

Thesis (M.S. in Systems Technology)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Orin Marvel, Curt Schleher. Includes bibliographical references (p. 71-74). Also available online.