Simulation of coarsening in three-phase solid oxide fuel cell anodes

Abstract

Coarsening of the nickel phase is known to occur in solid oxide fuel cell (SOFC) anodes consisting of Ni and yttria-stabilized zirconia (YSZ). However, the exact nature of the coarsening process is not known, nor how it affects three-phase boundaries (TPBs) and the resulting electrochemical performance. We apply a phase-field approach to simulate the microstructural evolution of Ni–YSZ anode functional layers. An experimentally obtained three-dimensional reconstruction of a functional layer from an anode-supported SOFC is used as the initial microstructure. The evolution of the microstructure is characterized quantitatively by examining the TPB density, interfacial area per unit volume, and tortuosity versus time. The assumed TPB contact angles are found to have a strong effect on the microstructural evolution; in particular, reducing the contact angle of nickel on YSZ yields less TPB reduction.