Nigel M. Sammes’s research while affiliated with Colorado School of Mines and other places

This chapter describes the concept, electrochemical reactions, and fabrication of a solid oxide fuel cell (SOFC). It initially describes how SOFC systems differ from other electrical devices and how they differ from other types of fuel cells, for example, they are all solid state (ceramics), run at high temperature, and have the potential for directly running off hydrocarbon fuels. Then the basic principles of the fuel cell are studied and each of the components described in more detail (the anode, cathode, and electrolyte). The discussion then moves on to how single SOFC’s can be stacked in a number of ways, to form systems, and what the advantages and disadvantages of each are. The chapter discusses one such SOFC system in more detail, that of the microtubular SOFC. Here, it examines how these microtubes are made, what they are made from, and how they have the potential for running at low temperature for small applications such as auxiliary power units (APU), for example. Then it deals with some micro- and macro-modeling on the microtubular SOFC, describing issues such as mass and thermal transport, the effect of altering a number of parameters, and how the modeling results compare to real data. Finally, the chapter concludes with some future directions on solid oxide fuel cells.

The performance of a conventional anode-supported microtubular SOFC using doped ceria as an electrolyte and Ni-based cermet as an anode is evaluated at low operating temperature between 294 and 542°C. An open-circuit voltage (OCV) of >0.9 V is obtained at all measured operating temperatures, and power generation is observed at temperatures as low as 294°C. The power density of the cell is 0.6 W/cm2 at 542°C operating temperature with 47% fuel utilization and is 5 mW/cm2 at 294°C operating temperature with an open-circuit voltage of 0.95 V. According to impedance spectroscopy, a greater influence of gas flow rate, on the cell performance, is observed at higher operating temperature.

IntroductionBasis of Electrochemical ReactorsSOFC and Related Research and DevelopmentMicro-SOFC DevelopmentElectrochemical DE-NOX Reactor and Other Applications for the Clean Car TechnologyReferences

We report the effect of a catalytic layer on a solid-oxide fuel cell (SOFC) anode surface on the fuel cell performance. A Ru/CeO2 catalytic layer has been applied on the anode surface and tested in the operating temperature of 650 and 700 °C. It has shown that application of the catalytic layer on the anode surface improves the cell performance especially at high fuel utilization condition. The energy efficiency at 0.7 V operating voltage has reached over 40% (LHV) below 700 °C operating temperature in flowing 20% H2–Ar fuel at the power density of over 0.5 W cm− 2.

This chapter describes the concept, electrochemical reactions, and fabrication of a solid oxide fuel cell (SOFC). The chapter initially describes how SOFC systems differ from other electrical devices and how they differ from other types of fuel cells; for example, they are all solid state (ceramics), run at high temperature and have the potential for directly running off hydrocarbon fuels. The chapter then studies the basic principles of the fuel cell, and describes each of the components in more detail (the anode, cathode, and electrolyte). The discussion then moves on to how single SOFC’s can be stacked in a number of ways, to form systems, and what the advantages and disadvantages of each is. Finally, the chapter discusses one such SOFC system in more detail, that of the microtubular SOFC. Here the chapter examines how these microtubes are made, what they are made from, and how they have the potential for running at low temperature for small applications such as auxiliary power units (APU), for example. The paper then concludes with some micro and macro-modeling on the microtubular SOFC, describing issues such as mass and thermal transport, the effect of altering a number of parameters, and how the modeling results compare to real data. The chapter concludes with some future directions on solid oxide fuel cells.

A water stable and water penetration free high lithium ion conducting solid electrolyte sheet of Li1.4Ti1.6Al0.4(PO4)(3) (LTAP) was prepared by hybridization with an epoxy resin. The LTAP fine powder was synthesized using a sol-gel method. A LTAP thin sheet (about 200 mu m) was prepared via a tape casting method using a slurry of the mixture of the fine LTAP powder and a TiO2 fine powder (3 weight%). The tape-cast green sheet was sintered at 1060 degrees C for 2 h. 2,2-bis(4-glycidyloxyphneyl)propane and 1,3-phenylenediamine in tetrahydrofuran was poured into the sintered LTAP sheet and was polymerized by heating at 150 degrees C for 24 h. The obtained LTAP-epoxy hybrid sheet was water-penetration free, and the electrical conductivity was 4x10(-4) Scm(-1) at 25 degrees C. This conductivity value is comparable to that of the sintered pellets reported previously. The lithium metal electrode protected with a lithium conducting polymer electrolyte, and the LTAP-epoxy hybrid electrolyte sheet showed no resistance change for 20 days in a saturated LiOH and LiCl aqueous solution. The water stable lithium metal electrode has a potential application for aqueous lithium air rechargeable batteries.

IntrosuctionExperimentalResults and DiscussionsConclusion Acknowledgement

A cathode-supported micro SOFC was prepared via co-sintering technique of a scandia-stabilized zirconia (ScSZ) electrolyte layer and a micro-tubular (La,Sr)xMnO3−δ (LSM) support, and subsequent deposition of various anode layers by dip-coating method. The micro-tubular SOFCs were electrochemically evaluated in a humidified H2 (3% H2O) atmosphere. An LSM-Ce0.9Gd0.1O1.95 activation layer was also introduced between the cathode tube and the electrolyte layer in order to improve the catalytic activation at the cathode side. The micro SOFCs exhibited a stable open circuit voltage above 1.05 V at 650 °C, and the cells with the anode film thicknesses of 8, 30 and 50 μm generated a maximum power density of 36, 49 and 126 mW/cm2, respectively. And, the cell with 50 μm thick anode layer showed about 10 times higher exchange current density than the others, which indicates that the anode performance on the cathode-supported micro SOFC was greatly affected by the thickness of the anode coating layer.

Sintering temperature is used to control the microstructure of Li1+x+yAlxTi2−xSiyP3−yO12 (x=0.3, y=0.2), a NASICON-type glass-ceramic. Scanning Electron Microscope imaging, X-Ray Diffraction, and Electrochemical Impedance Spectroscopy are employed to show that increase in sintering temperature increases conductivity while generating secondary crystalline phases. Total conductivity is as high as 3.81×10−4Scm−1 for sintering temperatures above 1000°C. Crystallization of dielectric phases places the optimal sintering temperature in the 900°C to 1000°C range. Thermal analysis of the glass precursor reveals the glass transition, and crystallization temperatures.