Ni/GDC Fuel Electrode for Low-Temperature SOFC and its Aging Behavior Under Accelerated Stress

The microstructural integrity of Ni-based fuel electrodes is important for long-term solid oxide fuel cell (SOFC) operation.
Degradation due to microstructural changes such as Ni-agglomeration, coarsening, and densification must be prevented by an
appropriate microstructure. Here, the performance of four types of nickel-ceria-based fuel electrodes, which differ concerning layer
sequence and manufacturing processes, was evaluated by electrochemical impedance spectroscopy at the nominal operating
temperature of 600 °C. Electrodes produced through screen-printed GDC exhibited an acceptable polarization resistance (0.260
Ωcm2 ), whereas electrodes with an additional printed Ni/GDC layer demonstrated inferior performance (0.550 Ωcm2 ). Electrodes
formed through infiltration of GDC into the printed GDC-layer displayed unreproducible performance values ranging from 0.16 to
1.20 Ωcm 2 despite similar processing. Conversely, electrodes with an extra layer of GDC infiltrated into the Ni-backbone exhibited
good performance (0.195 Ωcm 2 ) and stability. Accelerated degradation tests under OCV at increased operating temperatures of 700
and 900 °C were performed on the sample based on a GDC infiltrated Ni-backbone that performed best among reproducible
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samples. The polarization resistance at 600 °C recorded at the beginning and the end of life increased by up to 100%.
Microstructural analysis of the electrodes at different aging states revealed strong microstructural changes of fine-infiltrated GDC
structures and Ni agglomeration at higher operating temperature.