Performance and stability of large planar solid oxide fuel cells using phosphine contaminated hydrogen fuel

Coal syngas, a potential fuel for SOFCs, contains impurities like PH3, which rapidly degrade Ni-based SOFC anodes. Past research showed significant reconstruction of Ni anodes in button cells with degradation rates of similar to 0.5 mV.h(-1). It is not evident that these rates correspond to actual stack applications due to major differences in fuel utilization and delivery. Herein, a single planar repeat unit with an active area of 32.64 cm(2) is constructed using a Haynes (R) 242 manifold. The cell operates at 800 degrees C using dry H-2 with and without 10 ppm PH3. The cell employs a co-flow configuration with a fuel utilization of 12.5%. The performance of the cell is evaluated over 440 h by voltage-current measurements and electrochemical impedance spectroscopy. The post-run analysis of the contaminated cell is conducted via XRD, XPS and SEM. The degradation rate for the cell is found to be 3 x 10(-3) mV.h(-1), which is far lower than that reported previously. The cell shows low evidence of significant PH3 poisoning and there is no reconstruction of the Ni-anode microstructure, as seen in button cell testing. Some basic electrochemical and thermodynamic modeling, and microstructural/chemical characterization are presented and related to the cell's relatively stable performance observed in this work.