A numerical investigation of nitridation in solid oxide fuel cell stacks operated with ammonia

Operating solid oxide fuel cell (SOFC) stacks with ammonia induces the risk of nitriding in the fuel electrode and other metallic surfaces in the stack. This study aims to investigate the nitriding in the fuel electrode of an ammonia-fueled SOFC stack using a 3D Multiphysics model of a full stack. Based on the resulting species concentrations, a so-called nitriding potential is determined and compared to its critical level for various operating conditions and design modifications. The effects of the gas inflow temperatures, counter-flow configuration, and nickel coating over the inlet header of the stack are investigated. The results show that nitriding occurs in the first few centimeters of the fuel electrode for all investigated operating conditions considered in this study. Moreover, it is indicated that higher gas inflow temperatures and counter-flow configuration reduce the nitriding in the fuel electrode. Furthermore, the model illustrates the nitriding in the fuel active electrode for the gas inflow temperatures up to 700 °C. Finally, a significant reduction in nitriding in the fuel electrode is shown for a proposed nickel coating over the metallic inlet header due to a spreading of the ammonia decomposition.