Particle size dependence of polarization of Ni/YSZ cermet anodes for solid oxide fuel cells

A Monte Carlo simulation and the steady-state anodic polarization measurement have been performed to examine the particle size dependence of the polarization of nickel yttria-stabilized zirconia (Ni/YSZ) cermet anodes for solid oxide fuel cells. The triple-phase boundary (TPB) length in the model system is estimated by a Monte Carlo simulation using a simple cubic lattice model. The estimated TPB length is concave with respect to the nickel-volume fraction X for all particle-size combinations, and the maximal TPB length decreases as the size of the nickel or that of YSZ increases. The current–potential curve of the electrode reaction of the cermet anode has been estimated as a function of the sizes of the nickel particles and the YSZ particles on the basis of the calculated TPB length and the experimental data at X = 0.44 and at 1273 K. In the design of the SOFC anode, the estimated relation between polarization and particle size can be practically applicable to the range in which secondary particles do not form.

► We examine the triple-phase boundary(TPB) of Ni/YSZ cermet by computer simulation. ► The length is a concave function of the Ni-volume fraction with a maximal value. ► The maximal TPB length reduces with increasing the particle size of Ni or that of YSZ. ► We derive a steady-state current–potential curve as a function of particle sizes.