Computational fluid dynamics modeling of anode-supported solid oxide fuel cells using triple-phase boundary-based kinetics

Fuel oxidation in the solid oxide fuel cell occurs at the triple-phase boundary where electronic, ionic, and gas phases simultaneously interact. A quantitative knowledge of the triple-phase boundary density is therefore important in analyzing the fuel cell performance as well as designing the electrode structures and materials. In this work, the triple-phase boundary-based kinetics, developed from the patterned anode experiments are used in a computational fluid dynamics model to assess the performance of anode-supported nickel-yttria stabilized zirconia cells. The simulation results suggested that the effective triple-phase boundary density required to carry out the electrochemical oxidation reactions is several orders of magnitude lower when compared with the physical triple-phase boundary density of similar cermet anodes. The anode concentration gradients are found to be larger near the anode/electrolyte interface compared to that of fuel channel that is ascribed to the electrochemical reactions taking place in the anode active region and mass transport resistance of the microporous structure. The cell voltage decreased rapidly at high current density due to fuel starvation and subsequent drop of the exchange-current density. Furthermore, the effects of triple-phase boundary density and operating temperature on the cell performance are also studied and discussed.