H2 oxidation on Ni/Y-TZP cermet electrodes -: a comparison of electrode behaviour by GCI and EIS techniques

Reaction order and activation energy for H(2), oxidation on Ni/3 mol.% Y(2)O(3)-ZrO(2) (Ni/Y-TZP) cermet electrodes have been evaluated by galvanostatic current interruption (GCI) and electrochemical impedance spectroscopy (EIS) techniques. GCI data show a reaction order in P(H2O) of 0.4 and activation energy of 76 kJ mol(-1). In contrast, a first order with respect to P(H2O) and an activation energy of 169 kJ mol(-1) are obtained from EIS data. During GCI measurements, the actual H(2)O content or P(H2O)/P(H2) ratio at the electrode/electrolyte interface region could be significantly higher than that in the bulk electrode as H(2)O, the product of the reaction, remains in the gas phase. On the other hand, the H(2)O content at the interface region is very close to that in the bulk during EIS measurements under open circuit, It has been shown that H(2)O produced at the interface region during GCI measurements enhances the H, oxidation reaction, resulting in the shifting of the reaction rate dependency on H(2)O and activation energy to lower values as compared to those measured by EIS, (C) 1999 Published by Elsevier Science B.V. All rights reserved.