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Journal of the Electrochemical Society, Vol.161, No.14, F1366-F1374, 2014
Determination of Electrode Oxygen Transport Kinetics Using Electrochemical Impedance Spectroscopy Combined with Three-Dimensional Microstructure Measurement: Application to Nd2NiO4+delta
Oxygen reduction kinetic parameters - oxygen ion diffusion Dd, molar surface exchange rate O and surface exchange coefficient k -were determined for porous Nd2NiO4+delta solid oxide fuel cell cathodes as a function of temperature and oxygen partial pressure by analyzing electrochemical impedance spectroscopy data using the Adler-Lane-Steele model. Electrode microstructural data used in the model calculations were obtained by three-dimensional focused ion beam-scanning electron microscope tomography. Cathodes were fabricated using Nd2NiO4+delta powder derived from a sol-gel method and were tested as symmetrical cells with LSGM electrolytes. The oxygen surface exchange rate exhibited a power-law dependency with oxygen partial pressure, whereas the oxygen diffusivity values obtained varied only slightly. The present analysis suggests that the O-interstitial diffusion has a bulk transport path, whereas the surface exchange process involves dissociative adsorption on surface sites followed by O-incorporation. For Nd2NiO4+delta+ d at 700 degrees C and 0.2 atm oxygen pressure, Dd = 5.6.10(-8) cm(2)s(-1), O = 2.5 . 10(-8) mol . cm(-2) s(-1). The present Dd and O values and their activation energies are slightly different to those previously reported for Nd2NiO4+delta using other measurement methodologies, and lower than typical state-of-the-art Co-rich perovskites. However, the average kd = 1.0 10(-5) cm.s(-1) at 700 degrees C is comparable to those of fast oxygen exchange rate perovskites. (C) The Author(s) 2014. Published by ECS. All rights reserved.