Nickel/Zirconia

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. 

Dicks A.L., Pointon K.D., Siddle A., 2000. Intrinsic reaction kinetics of methane steam reforming on a nickel/zirconia anode. Journal of Power Sources 86, 523-530. 

The stack electrolytes are scandia-stabilised zirconia, about 140 (im thick. The air-side electrodes (anode in the electrolysis mode) are a strontium-doped manganite. The electrodes are graded, with an inner layer of manganite/zirconia ( 13 pm) immediately adjacent to the electrolyte, a middle layer of pure manganite ( 18 pm), and an outer bond layer of cobaltite. The steam/hydrogen electrodes (cathode in the electrolysis mode) are also graded, with a nickel-zirconia cermet layer ( 13 pm) immediately adjacent to the electrolyte and a pure nickel outer layer ( 10 pm). 

The basic elements of a SOFC are (1) a cathode, typically a rare earth transition metal perovskite oxide, where oxygen from air is reduced to oxide ions, which then migrate through a solid electrolyte (2) into the anode, (3) where they combine electrochemically with to produce water if hydrogen is the fuel or water and carbon dioxide if methane is used. Carbon monoxide may also be used as a fuel. The solid electrolyte is typically a yttrium or calcium stabilized zirconia fast oxide ion conductor. However, in order to achieve acceptable anion mobility, the cell must be operated at about 1000 °C. This requirement is the main drawback to SOFCs. The standard anode is a Nickel-Zirconia cermet. 

P. Holtappels, I. C. Vinke, E. G. J. de Haart, and U. Stimming. Reaction of hydro-gen/water mixtures on nickel-zirconia cermet electrodes II AC polarization characteristics. /. Electrochem. Soc. 146, (1999) 2976-2982. 

M. Cassidy, Q. Lindsay and K. Kendall, The reduction of nickel-zirconia cermet anodes and the effects on supported thin electrolytes, J. Power Sources, 61, p. 189 (1996)... 

There seems to be no alternative to the generation of stochastic composite structures and their solution by computer methods. In a series of papers, Sunde has treated the bulk resistivity and polarization resistance for the steady-state (Sunde [1996a, 1996b]) and the electrode impedance in the frequency domain (Sunde [1997,2000]). Although this work focused on nickel/zirconia anodes, the methodology is equally valid for other composite electrodes. The first step was to use the Monte Carlo... 

Holtappels P, Vinke IC, de Haart LGJ, Slimming U (1999) Reaction of hydrogen/water mixtures on nickel-zirconia cermet electrodes. 2. AC polarization characteristics. J Electrochem Soc 146 2976-2982... 

Takenaka ct al. studied the activity of various catalysts for carbon monoxide methanation in the absence of carbon dioxide [342]. From the different active species on a silica carrier, 5 wt.% ruthenium, 10wt% nickel and 10 wt.% cobalt were significantly more active than iron, palladium or platinum, each prepared with an active species content of 10 wt.%. Then Takenaka tested nickel, ruthenium and cobalt catalysts on different carrier materials, namely, alumina, silica, titania and zirconia. The formulations most active were nickel/zirconia and mthenium/ titania catalysts. The best performing catalyst was the 5 wt.% mthenium/titania, which converted the carbon monoxide apart from less than 20 ppm from a feed mixture containing 60 vol.% hydrogen, 15 vol.% carbon dioxide, 0.9 vol.% steam, 0.5 vol.% carbon monoxide, with a balance of helium at 220 °C. The space velocity was rather high at 300 L (hgcat) -... 

Choudhary and Goodman performed methane cracking over nickel/zirconia catalysts [102]. Two reactors had be switched in parallel for this process. Both the methane and the steam feed had to be switched between the two reactors, as shown in Figure 5.19. The optimum switching time between the processes was determined to... 

Coyle CA, Marina OA, Thomsen EC, Edwards DJ, Cramer CD, Coffey GW, Pederson LR (2009) Interactions of nickel/zirconia solid oxide fuel cell anodes with coal gas containing arsenic. J Power Sources 193 730-738... 

Marina OA, Pederson LR, Thomsen EC, Coyle CA, Yoon KJ (2010) Reversible poisoning of nickel/zirconia solid oxide fuel cell anodes by hydrogen chloride in coal gas. J Power Soinces... 

Faes A, Hessler-Wyser A, Presvytes D, Vayenas CG, Van Herle J (2009) Nickel-Zirconia anode degradation and triple phase botmdary quantification from microstmctural analysis. Fuel Cells 9 841-851... 

A.S. Ferlauto, D.Z. Deflorio, F.C. Fonseca, V. Esposito, R. Muccillo, and E. Traversa, Composites of Nickel, Zirconia and Carbon Nanotubes. In Solid Oxide Fuel Cells Vlll - Proceedings of the 8th International Symposium, ed. by S.C. Singhal, M. Dokiya. The Electrochemical Society Inc., New York, 2002 643-654... 

Bruce, L.A., Hope, G.J., and Mathews, J.F. (1983) The activity of cobalt-zirconia and cobalt-nickel-zirconia preparations in the Fischer-Tropsch reaction. Appl. Catai, 8 (3), 349-358. 

Empirical development of the nickel-zirconia anode over several decades has led to solid oxide fuel cells with adequate service life and performance, but fuel reforming is still required to operate with commercially available hydrocarbon fuels. It has become evident that the anode reactions are dominated by the three-phase boundary and that the microstructure of the composite cermet anodes is pivotal. Consequently, the processing methods used for making the anode powders, and the fabrication techniques used for deposition on the electrolyte are critical in making high performance anodes. Anode-supported cells with very thin electrolyte films are becoming interesting for operation at lower temperatures. 

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