Ni-based SOFC anodes: Microstructure and electrochemistry

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.