Determination of Electrode Oxygen Transport Kinetics Using Electrochemical Impedance Spectroscopy Combined with Three-Dimensional Microstructure Measurement: Application to Nd2NiO4+δ

KYLE YAKAL-KREMKI; L. MOGNI; A. CANEIRO; S. BARNETT

JOURNAL OF THE ELECTROCHEMICAL SOCIETY

ELECTROCHEMICAL SOC INC

Año: 2014 vol. 161 p. 1366 - 1374

0013-4651

Oxygen reduction kinetic parameters ? oxygen ion diffusion Dδ, molar surface exchange rate O and surface exchange coefficient k ? were determined for porous Nd2NiO4+δ 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+δ 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+δ at 700◦C and 0.2 atm oxygen pressure, Dδ = 5.6 · 10−8 cm2s−1, O = 2.5 · 10−8 mol · cm−2 s−1. The present Dδ and O values and their activation energies are slightly different to those previously reported for Nd2NiO4+δ using other measurement methodologies, and lower than typical state-of-the-art Co-rich perovskites. However, the average kδ = 1.0 10−5 cm ·s−1 at 700◦C is comparable to those of fast oxygen exchange rate perovskites. ©