Evaluation of electrochemical reaction mechanisms of La0.6Sr0.4CoO3-δ-Gd0.1Ce0.9O2-δ composite cathodes by 3D numerical simulation

In the present study, electrochemical reaction mechanisms of La0.6Sr0.4CoO3-δ (LSC)-Gd0.1Ce0.9O2-δ (GDC) composite cathodes for solid oxide fuel cell (SOFC) were evaluated by a Lattice Boltzmann Method (LBM) with 3D reconstructed cathode microstructures. Two electrochemical reactions, i.e. one which scales with the LSC surface area and the other with the triple phase boundary (TPB) length, were considered in the simulation. The exchange current density of the surface reaction was fitted with an experimental result of pure LSC cathode, and the TPB reaction exchange current density was fitted using the experimental results of LSC-GDC composites with various volume ratios. It is found for the LSC-GDC composite cathodes that the contribution from the TPB reaction dominates and that the effective reaction thickness elongates as the volume fraction of GDC is increased. It is considered that the performance enhancement of LSC-GDC composite cathode is attributed to both the improvement in effective ionic conductivity and the additional contribution from the TPB reaction.