Preparation and electrochemical characterisation of supporting SOFC–Ni–YZT anodes

Symmetrical cells consisting of Ni–Y0.20Ti0.18Zr0.62O1.90 (Ni–YZT) cermet electrodes on a Ni–YSZ support have been investigated with respect to the hydrogen/water partial pressures. Impedance spectra at open circuit potential were obtained as function of temperature and analysed in terms of a fractal finite length Gerischer Impedance. For fine and coarse microstructures of the Ni–YZT electrodes, a consistent set of model parameters could be obtained. The results indicate that surface diffusion rather than bulk diffusion plays a role in the hydrogen/water reaction but also that a fine-grained fraction in the mixed conducting YZT phase is advantageous for the overall electrode performance and the surface exchange reaction.