Effects of cathode thickness and microstructural properties on the performance of protonic ceramic fuel cell (PCFC) : a 3D modelling study

Abstract

Protonic Ceramic Fuel Cells (PCFCs) are promising power sources operating at an intermediate temperature. Although plenty of experimental studies focusing on novel material development are available, the design optimization of PCFC through numerical modelling is limited. In this study, a 3D PCFC model focusing on the cathode thickness and microstructure design is developed due to the high overpotential loss of the cathode. Unlike the 1D/2D models, the rib-size effects on the PCFC performance are fully considered when optimizing the cathode structure. Different from 1D/2D models suggesting thin cathode thickness, this study finds that the optimal cathode thickness is about 120–200 μm. In a thin cathode, weak O2 diffusion from the channel to the rib-covered cathode can lead to O2 depletion under the rib and very low local cell performance. By adjusting the cathode porosity from 0.3 to 0.5, nearly 9% performance improvement and 22.5% improvement in gas distribution uniformity can be achieved. When the cathode particle size changes from 0.1 μm to 0.2 μm, the O2 concentration under the rib increases nearly 50%. The optimal electronic phase volume fraction is suggested to be around 50–60% for achieving a balance between ohmic resistance and reaction sites. This model elucidates the relationship between cathode microstructure and PCFC performance comprehensively and can serve as a guiding tool for cell fabrication and future novel interconnect structure design.