Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains viii, 44 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 40-41).

Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves 74-78).

Thesis (M.S.)--Rochester Institute of Technology, 2003. / Typescript. Includes bibliographical references.

Solid oxide fuel cells (SOFC), owing to its high operating temperatures, have many advantages over other types of fuel cells. Its commercialization, however, relies greatly on its costs and long term durability. By reducing the operating temperature to the intermediate temperature range, the costs for the balance of plant would be significantly reduced. The greatest contribution to cell over-potential at this temperature range is the oxygen reduction at cathode; hence development of a cathode material with low specific resistance and durability would have direct impact on the commercialization of SOFC. Composite cathode is a common strategy used by many to improve cathode performance. This was done conventionally by random mixing of cathode material with a better ionic conductor such as the electrolyte material. Impregnation or infiltration is often used to improve interconnectivity among individual phases in the composite, In this study, fabrication of a composite cathode with two phases - gadolinium doped ceria (GDC) and platinum attempted, forming two inter-locked networks each with a channel dimension in the nanometer range by hard templating and chemical vapor infiltration (CVI) both for the first time to the best of my knowledge. It was found that surface layer of these materials play a very important role in the performance and structural stability. Another set of composite cathode was fabricated by packing commercially available GDC with carbon pore-former following by impregnation with Pt/Ag-Pt alloy. By introducing small amount of silver (6wt%), area specific resistance of 0.94cm2 and 0.16cm2 were observed at 550C and 660C, respectively during impedance spectroscopy in symmetrical cell arrangement. Silver was proposed to provide greater effective surface area for surface exchange and extending the triple phase boundary. Platinum was also suggested to provide a surface where silver wetting is possible stabilizing morphology of silver in the GDC scaffold. Platinum is not a practical choice of electrode material due to its costs and lower performance, it was chosen to demonstrate the strategy of vapor phase infiltration in fabricating SOFC composite cathode. However, the technique of CVI demonstrated can potentially be applied to other cathode candidate materials. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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This thesis investigates the possibility of using electrokinetic effects, induced when a colloidal system is subjected to an electric field, to produce deterministic structure in the catalyst layer of polymer electrolyte membrane fuel cells. The susceptibility of the catalyst ink system to electrokinetic effects is clearly demonstrated. A novel apparatus and procedure is developed to allow for the formation of continuous films between two electrode surfaces through solvent evaporation. Characterization of the resulting layers is done through imaging and rotating disc electrode measurements. While the images show some possibility of structure formation, no clear increase in the oxygen reduction rate is observed. Recommendations for extending this work are provided. / Thesis (Master, Chemical Engineering) -- Queen's University, 2010-01-06 17:29:23.27

Cost reduction is driving the development of solid oxide fuel cell (SOFC) technology for operations at lower temperatures (500 °C -700 °C) so as to allow the usage of cheaper balance-of-plant components and enhance the durability of the stack. However, lower temperatures adversely affect the overall performance of the cell and most notably that of the cathode. Development of cathode material exhibiting high performance at lower temperature is one of the goals of SOFC research and development. This thesis work is concerned with two distinct aspects of SOFC cathode development – one concerned with the stability of a recently studied cathode material, La0.5Ba0.5CoO3-δ (LBC), in CO2 containing atmosphere and another concerned with the development of methods for fabrication of reproducible electrodes and rapid electrochemical testing thereof. The study of reaction between LBC and CO2 was carried using a combination of thermogravimetric analysis (TGA), ex-situ X-Ray Diffraction (XRD) of products from TGA experiments and in-situ high-temperature XRD of LBC-CO2 mixtures. The mass change observed during TGA was combined with ex-situ XRD analyses of solid material phases to deduce the overall reactions. In-situ XRD measurements allowed for studying the intermediate reaction products. Isothermal studies at different temperatures in pure CO2 yielded kinetics for the reaction between LBC and CO2. Overall reaction pathway was proposed from these data. In addition, experiments were carried out to determine the thermodynamic carbonate formation temperature at a fixed CO2 partial pressure (pCO2). From the thermodynamic analysis of carbonate formation temperature at three different pCO2, the standard state enthalpy and entropy for the carbonate formation reaction were determined. This work is the first known in-depth study of reaction between LBC and CO2. The second distinct contribution of this thesis is the demonstration of a test system framework for fabricating reproducible miniature electrodes and rapid testing thereof. In particular, inkjet printing method was used to create well defined geometry of porous electrode and micro-contact impedance spectroscopy setup (MICS) was used to study the electrode electrochemical kinetics. The feasibility with electrode fabrication and electrochemical testing methods were demonstrated through the study of multiple silver miniature electrodes printed on single chip made of yttria-stabilized zirconia single crystal wafer. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-03-08 13:25:40.223

A numerical model for solid oxide fuel cells with Ni-infiltrated porous anode has been described. The novel contribution of the work is the development of a semi-continuous film model to describe the infiltrated Ni-phase. This model relates experimentally controllable parameters, namely, Ni- loading, porosity and pore size to the effective electronic conductivity of the Ni-phase and the number of active reaction sites or the triple phase boundary (TPB). The semi-continuous film model was incorporated in a two-dimensional (2D) SOFC model. The 2D model considers the coupled gas-phase transport, charge transport and electrochemical kinetics to directly examine the effect of Ni loading and porosity on the electrochemical performance of Ni-infiltrated SOFC anodes. From the semi-continuous film model, an optimal Ni loading that corresponds to a maximum in TPB length was identified. Comparison of effective electronic conductivity and TPB length for a Ni-infiltrated anode with those for a composite Ni-YSZ anode suggests that an infiltrated Ni anode with adequate electrical conductivity and sufficiently high TPB length can be fabricated even at a very low Ni loading. Comparison of various porous anodes with varying Ni loading, it was determined that maximum electrochemical performance does indeed correspond to anode with maximum TPB length. It was also determined that an infiltrated anode will have higher performance capabilities when compared to the conventional composite electrodes. However, degradation of performance may result due to degradation of connectivity in the infiltrated Ni. The methodology to model the latter effect was also proposed. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-06-13 13:09:49.182