CFD-simulation of effective carbon gasification strategies from high temperature SOFC Ni-YSZ cermet anodes

Carbon formation during internal reforming and irreversible nickel re-oxidation are main performance degradation sources of high temperature nickel-yttrium stabilized zirconia (Ni-YSZ) cermet anodes. In order to prolong the lifetime of electrodes and of solid oxide fuel cells (SOFCs), it is of key importance to find strategies to effectively and permanently gasify carbon deposits, that exclude the re-oxidation risk. Thus, this computational fluid dynamics (CFD) study scrutinizes four fundamentally diverse carbon gasification strategies, including carbon removal of a polarized cell, in the temperature range of 400-800 °C for their implementation in SOFC applications. Surface species that are precursors to before-mentioned degradation phenomena are temporally and spatially identified and resolved. Pure CO2, and a mixture of CO2 and O2 showed high carbon gasification rates. Nevertheless, a high nickel re-oxidation potential was identified. It is highlighted that humidified hydrogen and our novel approach of a polarized cell provided a safe gasification process by creating a reducing surface condition preventing from re-oxidation. These two methods can be used to extend a cell's lifetime and bring SOFCs closer to commercialization.