Advantages of ionic conductors over electronic conductors as infiltrates in solid oxide fuel cell cathodes

Abstract

To investigate the difference between ionic and electronic conductors as infiltrates in solid oxide fuel cells (SOFCs), high-throughput and high-performance finite element simulations were carried out on 51 different cathode microstructures. Five cathode backbones, reconstructed from a commercial SOFC, were infiltrated computationally with varying number densities of nanoscale electronically or ionically conducting particles. Local electrochemical quantities were computed within the volumetric meshes that represent the complex 3D microstructural morphologies that include the infiltrated particles. As infiltrates, ionic conductors improve the performance more than electronic conductors. By differentiating transport and reaction pathways originating from backbone phases and infiltrates, we show that new ionic transport pathways opened by the ionically conducting infiltrates are the origin of this difference. These new transport paths redistribute current throughout the cathode, thereby increasing (decreasing) the available local activation (Ohmic) overpotential at triple phase boundaries and rendering them more active than for the case of electronic conductors as infiltrates. These results give us insight to engineering improved electrodes for SOFCs via infiltration with surface active nano-particles.