Cyclic polarization enhances the operating stability of La0.57Sr0.38Co0.18Fe0.72Nb0.1O3-δ oxygen electrode of reversible solid oxide cells

Abstract

Reversing the direction of polarization current is essential for reversible solid oxide cells technologies, but its effect on cobaltite based perovskite oxygen electrodes is largely unknown. Herein, we report the operating stability and microstructure at the electrode/electrolyte interface of La0.57Sr0.38Co0.18Fe0.72Nb0.1O3-d (LSCFN) oxygen electrodes assembled on barrier-layer-free Y2O3–ZrO2 electrolyte under cyclic anodic/cathodic polarization mode at 0.5 A cm-2 and 750 °C. During the cyclic polarization, the electrocatalytic activity of LSCFN electrode is drastically deteriorated in cathodic mode, but the performance loss is largely recoverable in anodic mode. This is due to the fact that the surface segregation of Sr and accumulation at the electrode/electrolyte interface by cathodic polarization can be remarkably mitigated by anodic polarization. The time period in each cycle plays a key role in determining the accumulation of Sr species at the electrode/electrolyte interface. A full cell operating in a time period of 12 h fuel-cell/12 h electrolysis is reversible for a duration of 240 h, in contrast to the performance degradation in a shorter time period of 4 h fuel cell/4 h electrolysis. The present study sheds lights on applying cobaltite based perovskite oxygen electrodes on barrier-layer-free YSZ electrolyte for reliable solid oxide cells.