An effective property model for infiltrated electrodes is reported that predicts the dependence of effective electronic conductivity and active TPB length on experimentally controllable and measurable parameters. The model uses results from percolation theory and geometric arguments to compute the properties of Ni-infiltrated anodes of solid oxide fuel cells. While the predicted electronic conductivity is comparable to that for a typical composite Ni anode, the predicted effective TPB length is approximately two orders of magnitude higher for a Ni infiltrated anode with a Ni volume fraction of less than 10%. The predictions of the developed model are compared and validated against three independent experimental datasets. Parametric studies using this model suggest that decreasing the particle sizes of the infiltrated film and the substrate, as well as the substrate porosity will increase the active TPB length. While decreasing substrate particle size also increases the effective electronic conductivity of the electrode, decreasing substrate porosity has the opposite effect. Finally, a methodology is presented to quantitatively relate an experimentally observed degradation in effective electronic conductivity of infiltrated electrodes to a reduction in active TPB length as a function of time.

SOFC anodes fabricated by Ni-impregnation of porous YSZ support have a microstructure distinct from the much studied/modeled conventional Ni-YSZ composite anodes. The Ni-infiltrated anode forms a semi-continuous network of electron conducting Ni-phase on the YSZ support framework. In this study, the Ni phase was modeled as a two-dimensional film on the porous YSZ structure and percolation theory was utilized to evaluate the following features that are unique to Ni-impregnated YSZ anodes - (i) the electrical conductivity of a semi-continuous film of nickel formed on the YSZ support framework, and (ii) the active TPBs in a nickel impregnated system based on the semi-continuous nature of the nickel phase. The effect of Ni loading relative to the total pore volume on electronic conductivities and TPB densities is evaluated and compared to literature.

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