Numerical Study on Mass Transfer and Electrical Performance of Anode-Supported Planar Solid Oxide Fuel Cells with Gradient Porosity Anode

Microstructure modification of thick anode is an effective way to enhance cell performance of the anode-supported planar solid oxide fuel cells (SOFCs). In this work, the influence of multilayer anode microstructure with gradient porosity on cell mass transfer and electrical performance is numerically investigated. The coupled phenomena of fluid flow, multicomponent mass transfer, charge transport, and electrochemical reactions of SOFC, in three-dimensions (3D), are simulated by using the finite element computational fluid dynamics approach. Quantitative analyses of hydrogen concentration and anodic overpotentials are conducted to better understand the effect mechanism of the gradient porosity anode on the cell performance. The effect of gradient porosity distribution on the cell performance is also systematically discussed. It is found that the gradient porosity anode can significantly enhance the cell mass transfer performance to reduce the anodic concentration overpotential. The combined effects of activation, concentration, and ohmic overpotentials can effectively improve the cell electrical performance. For the cases studied, porosity gradient and porosity of anode functional layer 2 (AFL2) both range from 0.1 to 0.3. Results indicate that increasing the porosity gradient or porosity of AFL2 can enhance the cell mass transfer performance. As the porosity of AFL2 is higher than 0.2, the gradient porosity anode design is beneficial to improve the cell electrical performance.