Functional grading design of solid oxide fuel cell anodes: Insights from fabrication to operation simulations

Functional graded (FG) electrodes can enhance the performance of solid oxide fuel cells (SOFCs). In this work, a numerical framework is proposed for optimizing the microstructure of FG composite anodes in SOFCs. The processes of powder packing, powder sintering, and electrochemical reactions for the anodes are simulated using the discrete element method, kinetic Monte Carlo, and finite volume method, respectively. The influences of different porosity, particle size and composition gradients on the performance of the anodes were studied. The results demonstrate the significance of the microstructure near the electrolyte region to the electrochemical performance. With the increase of the gradient exponent P will enhance the gas diffusion capacity of the anodes with porosity gradient and size gradient. Furthermore, the performance of the porosity-graded anodes will improve with the increase of P, while the particle size-graded anodes may have different performance influence trends due to the level of current density. The research further pointed out that when the porosity near the electrolyte region decreased to below 0.3, the improvement of anode performance was not obvious, while the particle size decreased to 0.3 μm significantly enhanced it. The study also found that an increase in YSZ content could promote ion transport, thereby significantly improving anode performance, whereas the composition gradient had little effect. The proposed numerical framework can potentially be extended and adapted for the rational design of functionally graded SOFC cathodes and other electrodes with different material systems, by optimizing the fabrication process of SOFCs.