Lattice Boltzmann modelling of the coupling between charge transport and electrochemical reactions in a solid oxide fuel cell with a patterned anode

A fundamental understanding of the electrochemical reactions and the associated transport processes in electrodes of solid oxide fuel cells (SOFCs) is critical to the development of new electrode materials. To date, however, our understanding of the electrode processes is still very limited due to the lack of well-designed experiments and carefully-validated predictive models. To facilitate studies in this area, we have developed a numerical model that has taken into consideration of the coupling between the transport of mobile charged species (e.g., ions and electrons) in conducting phases and the electrochemical reactions at the three phase boundaries of an SOFC anode. The validity of this model has been confirmed by the electrochemical performance of test cells with a patterned anode consisting of well-defined electronic and ionic conducting phases. The model is then applied to quantifying the factors that critically influence the performance of a patterned anode, resulting in three key dimensionless parameters governing the coupling of transport and reactions in the anode: the ratio of electronic-to-ionic conductivity (σ_el/σ_ion), the dimensionless exchange current density (i_ex/i₀), and the dimensionless electric potential (Fϕ₀/RT). In particular, it is found that only i_ex/i₀ and Fϕ₀/RT play a significant role under typical SOFC operating conditions: anode performance increases with the increase in i_ex/i₀ and Fϕ₀/RT. Accordingly, we have constructed a phase map to demonstrate the combined effect of i_ex/i₀ and Fϕ₀/RT, which is helpful for rational design and operation of SOFC patterned electrodes of different materials and geometries. More importantly, our present model is also applicable to the study of actual porous SOFC electrodes with known 3D microstructures.