Mechanism and kinetics of oxygen reduction on porous Nd2NiO4+δ electrodes with different microstructures.

L. MOGNI; A. MONTENEGRO HERNANDEZ; K. YAKAL-KREMSKI; A. CANEIRO; S. BARNETT

Mount Holyoke

Congreso; Gordon Research Conference: Solid State Studies in Ceramics; 2014

Gordon Conference

Measurement of the oxygen transport kinetics of MIEC oxides is important to select the appropriate materials and tounderstand their performance in solid oxide fuel cells (SOFCs). Particularly, the nickelates belonging to the RuddlesdenPopperphases Nd2NiO4+δ(NNO) have been proposed as oxygen electrode for fuel and electrolyze cells [1]. This oxide hasthe particularly of to exhibit O-ion transport by an O-interstitials mechanism.The diffusion (D) and surface exchange (k) coefficients of the NNO oxides have been evaluated by oxygen isotopicexchange [2] and conductivity relaxation [3]. However, these results are not fully reliable because, among other issuesassociated with these techniques, it is difficult to obtain dense single-phase NNO samples required for thesemeasurements. This is due to the high sintering temperatures (1350 °C), which induce Ni evaporation.In this work, the D and k coefficients for NNO nickelates were evaluated by applying a method where the kineticsparameters are obtained from electrochemical measurements on as used electrode materials. This method is based on theAdler-Lane-Steele (ALS) model for the electrochemical response of a macro-homogeneous porous electrode [4] utilizing asinput both the EIS data and the electrode morphology information [5-6].The same analysis is applied to three NNO samples obtained by different routes and with characteristic microstructures [7]with the aim of to identify the validity of the method and the confiability of the results.