Importance of Anode Microstructure in Modeling Solid Oxide Fuel Cells

A one-dimensional button-cell model is developed and applied to explore the influence of anode microstructure on solid oxide fuel cell (SOFC) performance. The model couples porous-media gas transport and elementary electrochemical kinetics within a porous Ni-YSZ cermet anode, a dense YSZ electrolyte membrane and a composite LSM-YSZ cathode. In all cases the fuel is humidified H2 and air is the oxidizer. The effects of porosity, tortuosity, and other microstructural geometric factors are evaluated with respect to their overpotential contributions. The model is used to assist interpretation of the experimental results reported by Zhao and Virkar (J. Power Sources, 141:79-95, 2005). It is shown that there must be a physically reasonable positive correlation between porosity and tortuosity. The results also show that reducing anode porosity, which increases mass-transfer resistance, can significantly increase the thickness of the electrochemically active region.