Electrode cermet

Clearly, the effective conductivity of a porous cermet electrode with a given composition (Ni to YSZ ratio) and phase distribution changes with porosity. When NiO particle size was reduced, the porosity of the cermet would be decreased as well [31,32] Equation (2.1) suggests that the effective conductivity increases as the porosity is reduced [15],... 

Jiang SP and Badwal SPS. An electrode kinetics study of H2 oxidation on Ni/Y203-Zr02 cermet electrode of the solid oxide fuel cell. Solid State Ionic 1999 123 209-224. 

Matsuzaki Y and Yasuda I. Effect of a sulfur-containing impurity on electrochemical properties of a Ni-YSZ cermet electrode. In Yokokawa H, Singhal SC, editors. Proceedings of the Seventh International Symposium on Solid Oxide Fuel Cells (SOFC-VII), Pennington, NJ The Electrochemical Society, 2001 2001(16) 769-779. 

Wang, L.S. et ah, Sputter deposition of yttria-stabilized zirconia and silver cermet electrodes for SOFC applications, Solid State Ionics, 52, 261-267 (1992). 

In the NGASE operation both the anode gas (methane-steam) and cathode gas (hydrogen-steam) are reducing (low ), and thus both electrode materials must be capable of low Po stability. A Ni-based cermet electrode for both anode and cathode will be appropriate for this mode of operation. The authors have observed erosion of zirconia electrolyte at temperatures above 700°C under these conditions. This phenomenon may limit the usefulness of the NGASE process. 

At temperatures below 1000°C the doped ceria has a considerable larger polarisation resistance, Rp, even in case of cermet with nickel. (The reaction rate is proportional to 1/Rp). At the lower temperatures the reaction may be accelerated by addition of fine Ni particle to the surface of the doped ceria. Impedance spectra at 850°C of Ni/Ceo jGdo iO, 95 cermet electrodes with and without small amounts of fine Ni particles (probably of nanometer size) are given in Fig. 15.13. The impedance is significantly affected. The dominant low frequency arc (fsummit = 1 Hz)... 

Figure 15.13. Impedance spectra for Ni/Ceo9Gdo.iOi 95 (CGI) cermet electrodes on YSZ foils at 850°C in Hj + 3% H2O after correction for active electrode area, as sintered, and after addition of 3 w/o fine Ni.

Key words Combustion Synthesis/Strontium Titanate/Cermet/Electrode Fuel Cell... 

A DIRECT METHANOL FUEL CELL USING CERMET ELECTRODES IN LOW TEMPERATURE COFIRE CERAMICS... 

A Direct Methanol Fuel Cell Using Cermet Electrodes... 

In this work, a cermet electrode structure is developed for the anode structure using a porous borosilicate structure as the mechanical base for the anode structure coated with a thin silver film from the reduction of Ag resinate film to provide a conductive base. The electrode catalysts were added by the reduction of a mixture of platinum/ruthenium resinate. 

Figure 9-2 shows the discharge curve of borosilicate electrode versus the standard carbon electrode of the H-Tec fuel cell. The load across the fuel cell for this test is 10 Q, resulting in a discharge of 100 mA cm. The cermet electrode demonstrates minimal increases of impedance over the discharge period and the higher overall voltage. The maximum developed by borosihcate substrate is 0.3489 V. This demonstrates that Ag metallization with a platinum/ruthenium catalyst can be developed as a cathode structure in DMFCs. 

Figure 9-7a,b is SEM images of the cermet electrode at high and low magnification. 

Figure 9-9. Selected area electron diffraction pattern of Ag cermet electrode...

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. 

B. de Boer. SOEC Anode hydrogen oxidation at porous nickel and nickel/yttria stabilized zirconia cermet electrodes. Ph.D. thesis. University of Twente, The Netherlands 1998. 

Mogensen et al. [24] investigated Ni/YSZ cermet electrodes at 1273 K and found the electrode impedance to be formed by a low-fiequency contribution, with resistance decreased by increasing both the partial pressure of hydrogen and water, and a high-frequency contribution with resistance and capacitance almost independent of the partial pressures of hydrogen and water. The proposed model does not respect the stoichiometry of the electrochemical reaction ... 

Sonn V, Leonide A, Ivers-Tiffee E. Combined deconvolution and CNLS fitting approach applied on the impedance response of technical Ni/8YSZ cermet electrodes. J Electrochem Soc 2008 155(7) B675. 

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... 

Boer, B.d. PhD Thesis, Hydrogen oxidation at porous nickel and nickel/yltriastabilised zirconia cermet electrodes, in Inorganic Materials- Faculty of Chemical Engineering)99S, University of Twente ISBN 90-36511909. 

Matsuzaki, Y. and Yasuda, I., Electrochemical characteristics of aNi-YSZ cermet electrode of YSZ in a H2-H2O-CO-CO2 system, inProceedings of Solid Oxide Fuel Cells VI, S.C. Singhal and M. Dokiya (Eds.), 1999, p. 560. 

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