Effect of Cathodic Polarization on the La0.6Sr0.4Co0.2Fe0.8O3-δ - Cathode/Gd-Doped Ceria-Interlayer/YSZ Electrolyte Interfaces of Solid Oxide Fuel Cells

Evaluation of the interfaces is critical for improved long-term stability and performance of solid oxide fuel cells (SOFC) under required operating conditions. In this work, cells consisting of LSCF-cathode vertical bar GDC-interlayer vertical bar 8YSZ-electrolyte vertical bar Pt-anode were tested under open-circuit voltage (OCV) and cathodic polarization at a constant current of -0.3 A at 800 degrees C for 300 h in air. Dense GDC films by pulsed laser deposition (PLD) were used as reaction barrier layers. The results showed that after cell tests, SrZrO3 formed at the LSCF/GDC interface in consequence of the fast Zr migration in the PLD-grown GDC interlayers. However, SrZrO3 formation and GDC microstructural feature differ between OCV and cathodic polarization. Under OCV, SrZrO3 laterally formed at the O-2/LSCF/GDC triple phase boundary with GDC interlayer showing increased porosity near the YSZ electrolyte. Both of these led to a drastic increase in polarization resistance with time. Under cathodic polarization, localized transverse growth of SrZrO3 was observed, and an apparent pore elimination occurred in GDC. Cells also showed no performance degradation under cathodic polarization. Based on the above observation, a plausible cation diffusion behavior and oxygen transport is discussed. (C) 2017 The Electrochemical Society. All rights reserved.