Electrochemical analysis for the identification of electrode reaction in Ni-YSZ anode as for Solid oxide fuel cell

摘要

The impedance of Ni-YSZ cermet electrodes was investigated as a function of different partial pressure of hydrogen and water. The impedance spectra for the hydrogen/water reaction show two reactions by DRT analysis. Reaction at high-frequency region was assigned to transport of electrode - oxidation reaction within the electrode structure and the electrode / electrolyte interface. Whereas low frequency response is the adsorption of a gaseous H_2O molecule from the gas phase onto the active electrode site. The data are analyzed using an equivalent circuit representing two parallel RC. The values of activation overpotential are separated under the fixed current load, which are well-fitted to the Butler-Volmer equation. Under the current load, the variation of exchange current density ( i_0 ) with pO_2 indicated that the total reaction-rate is determined by charge transfer reaction at the high temperature.