Overstoichiometric oxides Ln2NiO4+δ (Ln = La, Pr or Nd) as oxygen anodic electrodes for solid oxide electrolysis application

Improving the oxygen electrode performances of the single solid oxide electrolysis cell (SOEC) is of peculiar interest as it contributes to a large extent to the cell polarization resistance. The present study focuses on alternative oxygen electrode materials: the oxygen overstoichiometric rare-earth nickelate oxides Ln(2)NiO(4+delta) (Ln = La, Pr or Nd). Their electrochemical properties are measured on three-electrode symmetrical half-cells under zero dc conditions and under anodic polarization. The electrochemical characteristics are compared to those of the usual perovskite La0.6Sr0.4Fe0.8Co0.2O3-delta (LSFC) electrode. Under polarization, in the temperature range from 600 degrees C to 800 degrees C, the Pr2NiO4+delta-based cells exhibit the highest performances. At the same anodic overpotential of 0.15 V/Pt/air, the current densities measured through Pr2NiO4+delta nickelate-based cells are more than ten times larger than those obtained with a cell based on LSCF. The modeling of the anodic overpotential phenomena (activation and concentration terms) occurring at the oxygen electrode is achieved and discussed. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.