Enhanced Performances of Structured Oxygen Electrodes for High Temperature Steam Electrolysis

Authors


  • Paper presented at the 10th European SOFC Forum 2012, June 26–29, 2012 held in Lucerne, Switzerland. Organized by the European Fuel Cell Forum – www.efcf.com

Abstract

The present study is focused on alternative structured oxygen electrodes for solid oxide electrolysis cells (SOEC). The Ln2NiO4+δ (Ln = La or Pr) nickelate oxides were selected as innovative electrode materials with respect to their mixed electronic and ionic conductivity. A thin interfacial ceria-based layer was added in between the electrode and the zirconia-based electrolyte to improve mechanical and electrochemical properties and to limit the chemical reactivity. These structured cells were characterized by electrochemical impedance spectroscopy on symmetrical cells, under zero dc conditions and anodic polarization. Low polarization resistance RP and improved anodic overpotential ηA versus current density curves were obtained for the Pr2NiO4+δ electrode with Ce0.8Y0.2O2–δ interlayer: RP is decreased down to 0.06 Ω cm2 at 800 °C, under air and zero dc conditions. Then, complete hydrogen electrode-supported cells including Pr2NiO4+δ as oxygen electrode were electrochemically characterized. At 800 °C, when the inlet gas composition is 90 vol.% H2O–10 vol.% H2 at the hydrogen electrode, air being swept at the oxygen electrode, the current density determined at 1.28 V reaches –0.9 A cm–2, the corresponding steam to hydrogen conversion ratio being 58%. These results are compared to those obtained with a reference cell including the oxygen deficient perovskite La0.6Sr0.4Fe0.8Co0.2O3–δ as oxygen electrode.

Ancillary