The electrochemical behavior of Ni-based SOFC anodes with different microst
ructures was studied. The anodes consisted either of a Ni gauze, a Ni patte
rn, a Ni paste, or a Ni-YSZ cermet. According to electrochemical impedance
spectroscopy (EIS) measurements, the anodes are dominated by two main proce
sses. The high frequency process decreases exponentially with an applied ov
erpotential and is thermally activated with an activation energy of around
1 eV. The process could be attributed to the adsorption of hydrogen includi
ng charge transfer. The low frequency impedance arc arises only under a hig
h overpotential applied between the working and the reference anode. The im
pedance of this process increases the higher the overpotential and is therm
ally activated with an activation energy of 0.5 eV. This process is assigne
d to the desorption of water.