Mass Transfer in Functionally Graded Solid Oxide Fuel Cell Electrodes

A 1-D computational model is presented in which performance of a solid oxide fuel cell with functionally graded electrodes can be predicted. The model calculates operational cell voltages with varying geometric and operational parameters. The model accounts for losses from mass transport through the porous electrodes, ohmic losses from current flow through the electrodes and electrolyte, and activation polarization. It also includes a model for the full or partial internal reforming of methane. The model was applied to investigate the effect of electrode porosity distribution on performance. Specifically the physical phenomena that occur when the electrode is designed with a change in microstructure along its thickness is studied. The general trends that occur are investigated to find the arrangement for which the minimal polarization occurs. Both diluted hydrogen fuel and partially reformed methane streams are investigated. It is concluded that performance benefits are seen when the electrodes are given an increase in porosity near the electrolyte interface.