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Synthesis and Performance of Sol-Gel Prepared Ni-YSZ Cermet SOFC Anodes

2005; Institute of Physics; Volume: 152; Issue: 3 Linguagem: Inglês

10.1149/1.1855875

1945-7111

Peter Keech, Danielle E. Trifan, Viola Birss,

Fuel Cells and Related Materials

Sol-gel derived (SD) NiO-YSZ particles were formed from metallic nitrate and butoxide precursors, and after heat-treatment at 1000°C, the NiO and yttria-stabilized zirconia (YSZ) average particle sizes were found to be less than 50 and 30 nm, respectively, as measured using X-ray diffraction and transmission electron microscopy. In both cases, small particles were observed as larger agglomerates, up to 100 nm in size. The SD powders were suspended in ethanol and sprayed onto YSZ disks, roughened with a thin layer of pure SD YSZ to improve active layer adhesion. Electrochemical evaluation (low- and high-field cyclic voltammetry and impedance spectroscopy) was carried out in a half-cell configuration at 800°C in a 3% mixture. The exchange current density, obtained from all three methods, was found to agree only if a two-step hydrogen oxidation reaction was assumed, and the relatively low Tafel slope obtained suggests that the second electron-transfer step may be rate limiting. By comparison with ceramic grade (CG) Ni-YSZ, our results indicate an initial tenfold higher performance for the SD Ni-YSZ. However, a gradual loss of performance was observed for the SD electrodes that was not seen with the CG materials, possibly attributed to the thinness of the SD active layer. © 2005 The Electrochemical Society. All rights reserved.