Characterization of Ni-YSZ anode degradation for substrate-type solid oxide fuel cells

Substrate-type planar solid oxide fuel cells with an effective electrode area of 10 cm(2) and reference electrodes were fabricated and run for 211 and 1015 h to investigate Ni-YSZ anode degradation. An Ni-YSZ anode degradation of 14 mu V/h at a current density of 0.3 A/cm(2) was determined by impedance analysis. Mercury porosimetry revealed that the Ni-YSZ anode substrate had two pore distribution peaks in the radius ranges of 10 to 200 and 200 to 50,000 nm before testing; the pore distribution peak in the radius ranges of 10 to 200 nm shifted so far in the direction of large pore radius ranges that it almost disappeared after 1015 h. Scanning electron microscopy-electron probe microanalysis observations showed that the diameter of Ni particles in Ni-YSZ anode substrates was about 0.1 to 1 mu m before running and after 211 h, whereas they increased up to 10 mu m after 1015 h. According to these results, Ni-YSZ anode degradation was due to a decrease of the specific surface area of Ni particles caused by Ni sintering in the Ni-YSZ anode substrate.