Exploring remedies for PH_3 poisoning of a Ni-YSZ anode in coal-syngas fuel

摘要

Ni-YSZ cermet is commonly used as the anode of a solid oxide fuel cell (SOFC) because it has excellent electrochemical performance and is a cost effective anode material for coal-syngas fuel. However, coal-syngas contains trace contaminants, such as phosphine (PH_3), hydrogen sulfur (H_2S), arsine (AsH_3) and stibine (SbH_3), and these can cause degradation of the SOFC. Ni-YSZ anode-supported SOFCs were exposed to syngas and H_2 fuel, while co-feeding PH_3 and chlorine Cl_2 impurities under a constant current load at 800°C. The cell degradation was postponed in syngas and highly mitigated in H_2. In another test, a Ni-based filter was used to remove the PH_3 impurity. The results show that the filter can effectively remove 20 ppm PH_3 to a level which does not significantly degrade the SOFC over 400 h. The poisoning effects were evaluated by current-voltage scans and impedance spectroscopy, in addition to thermodynamic and chemical analyses. The postmortem analyses of the cell and filter were performed by means of XRD and SEM/EDS.