Zirconia fuel cell

M. Hsu, "Zirconia Fuel Cell Power System," 1985 Fuel Cell Seminar Abstracts, 1985 Fuel Cell Seminar, Tucson, AZ, May 19-22, 1985. 

In the same line of electrocatalytic applications, some perovskites have been shown to be suitable cathode materials in high-temperature fuel cells (256, 257). Successful and economical operation of a high-temperature zirconia fuel cell has been achieved by means of porous PrCo03 cathodes. With hydrogen as the fuel and oxygen as the oxidant, power densities of... 

Mesoporous zirconia Mesoporous zirconia fuel cell catalyst Mesostructural transformation Metal aluminophosphates 04-P-l 1... 

And now briefly about modem Ukrainian fuel cell history Being based on many years positive experience in manufacture of real nano-sized zirconia powders with different stabilizers like yttria, calcia, scandia etc. and zirconia ceramics [8, 9] the first Ukrainian demonstrating model of zirconia fuel cell was made and exhibited by January 22, 2002 [10- 12]. It has realized 0.85 V and 0.5 V of electro motive forces with propane gas and ethanol respectively at their direct burning. 

The tape-casting method makes possible the fabrication of films in the region of several hundred micrometers thick. The mechanical strength allows the use of such a solid electrolyte as the structural element for devices such as the high-temperature solid oxide fuel cell in which zirconia-based solid electrolytes are employed both as electrolyte and as mechanical separator of the electrodes. 

The deposition of thin conductive oxide films on flat zirconia components has also received considerable attention both for fuel cell applications20 and also for SEP21 and NEMCA studies.22,23 The interested reader is referred to the original references for experimental details. 

The stability of ceramic materials at high temperatures has made them useful as furnace liners and has led to interest in ceramic automobile engines, which could endure overheating. Currently, a typical automobile contains about 35 kg of ceramic materials such as spark plugs, pressure and vibration sensors, brake linings, catalytic converters, and thermal and electrical insulation. Some fuel cells make use of a porous solid electrolyte such as zirconia, Zr02, that contains a small amount of calcium oxide. It is an electronic insulator, and so electrons do not flow through it, but oxide ions do. 

A hydrogen fuel cell is environmentally friendly, but H2 is much more difficult to store than liquid fuels. The production, distribution, and storage of hydrogen present major difficulties, so researchers are working on fuel cells that use liquid hydrocarbon fuels. One such fuel cell is composed of layers of yttria-stabilized zirconia (YSZ), which is solid Zr02 containing around 5% Y2 O3. This cell uses the combustion of a... 

Figure 6.18 Schematic diagram of a fuel cell stack using a stabilized zirconia electrolyte.

Liu J and Barnett SA. Thin yttrium-stabilized zirconia electrolyte solid oxide fuel cells by centrifugal casting. J Am Ceram Soc 2002 85 3096-3098. 

Kawada T, Sakai N, Yokokawa H, Dokiya M, Mori M, and Iwata T. Characteristics of slurry-coated nickel zirconia cermet anodes for solid oxide fuel cells. J Electrochem Soc 1990 137 3042-3047. 

Hikita T. Research and development of planar solid oxide fuel cells at Tokyo Gas. In Badwal SPS, Bannister MJ, Hannink RHJ, editors. Science and Technology of Zirconia V., Lancaster, PA Technical Publishing Company, 1993 674—681. 

Primdahl S, Sprensen BF, and Mogensen M. Effect of nickel oxide/yttria-stabilized zirconia anode precursos sintering temperature on the properties of solid oxide fuel cells. J Am Ceram Soc 2000 83 489 -94. 

Wen C, Kato R, Fukunaga H, Ishitani H, and Yamada K. The overpotential of nickel/ yttria-stabilized zirconia cermet anodes used in solid oxide fuel cells. J Electrochem Soc 2000 147 2076-2080. 

The perovskite oxides used for SOFC cathodes can react with other fuel cell components especially with yttria-zirconia electrolyte and chromium-containing interconnect materials at high temperatures. However, the relative reactivity of the cathodes at a particular temperature and the formation of different phases in the fuel cell atmosphere... 

M. Mamak, N. Coombs, and G. Ozin, Mesoporous yttria-zirconia and metal-yttria-zirconia solid solutions for fuel cells, Adv. Mater. 12, 198—202 (2000). 

N. Kiratzis, P Holtappels, C. E. Hatchwell, M. Mogensen, and J. T. S. Irvine, Preparation and characterization of copper/yttria titania zirconia cermets for use as possible solid oxide fuel cell anodes, Fuel Cells 1,211-218 (2001). 

P Ratnasamy, Crystalline, mesoporous ceria—zirconia based reforming catalysts for PEM fuel cells. Preprints Symp.—Am. Chem. Soc., Div. Fuel Chem. 46,635—640 (2001). 

It has been observed that solid oxide fuel cell voltage losses are dominated by ohmic polarization and that the most significant contribution to the ohmic polarization is the interfacial resistance between the anode and the electrolyte (23). This interfacial resistance is dependent on nickel distribution in the anode. A process has been developed, PMSS (pyrolysis of metallic soap slurry), where NiO particles are surrounded by thin films or fine precipitates of yttria stabilized zirconia (YSZ) to improve nickel dispersion to strengthen adhesion of the anode to the YSZ electrolyte. This may help relieve the mismatch in thermal expansion between the anode and the electrolyte. 

O. Yamamoto, et ah, "Zirconia Based Solid Ion Conductors," The International Fuel Cell Conference Proceedings, NEDO/MITI, Tokyo, Japan, 1992. 

A key factor in the possible applications of oxide ion conductors is that, for use as an electrolyte, their electronic transport number should be as low as possible. While the stabilised zirconias have an oxide ion transport number of unity in a wide range of atmospheres and oxygen partial pressures, the BijOj-based materials are easily reduced at low oxygen partial pressures. This leads to the generation of electrons, from the reaction 20 Oj + 4e, and hence to a significant electronic transport number. Thus, although BijOj-based materials are the best oxide ion conductors, they cannot be used as the solid electrolyte in, for example, fuel cell or sensor applications. Similar, but less marked, effects occur with ceria-based materials, due to the tendency of Ce ions to become reduced to Ce +. 

Figure 29. Conductivity of some intermediate-temperature proton conductors, compared to the conductivity of Nafion and the oxide ion conductivity of YSZ (yttria-stabilized zirconia), the standard electrolyte materials for low- and high-temperature fuel cells, proton exchange membrane fuel cells (PEMFCs), and solid oxide fuel cells (SOFCs).

For the purposes of review. Figure 1 illustrates the basic function of the cathode in a solid oxide fuel cell. Whether acting alone or as part of a stack of cells, each cell consist of a free-standing or supported membrane of an oxygen-ion-conducting electrolyte, often yttria-stabilized zirconia (YSZ). Oxygen, which is fed (usually as air) to one side of the membrane, is reduced by the cathode to oxygen ions via the overall half-cell reaction... 

Solid oxide fuel cell (SOFC) working between 700 and 1000 °C with a solid oxide electrolyte, such as yttria-stabilized zirconia (Zr02-8% Y2O3), conducting by the... 

Catalysts. - Group VIII metals, conventional base metal catalysts (Ni, Co, and Fe) as well as noble metal catalysts (Pt, Ru, Rh, Pd) are active for the SR reaction. These are usually dispersed on various oxide supports. y-Alumina is widely used but a-alumina, magnesium aluminate, calcium aluminate, ceria, magnesia, pervoskites, and zirconia are also used as support materials. The following sections discuss the base metal and noble metal catalysts in detail, focusing on liquid hydrocarbon SR for fuel cell applications. 

YSZ is the usual material for use in solid oxide fuel cells. Another interesting application of stabilized zirconia is in the detection of oxygen, where it is used in both oxygen meters and ojg gen sensors, which are based on a specialized electrochemical cell (Section 5.4.4). 

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