Effects of water on oxygen surface exchange and degradation of mixed conducting perovskites

The effects of water on oxygen surface exchange kinetics and its degradation of dense La0.6Sr0.4CoO3−δ (LSC) thin films on yttria-stabilized zirconia (YSZ) are investigated by impedance spectroscopy and X-ray photoelectron spectroscopy (XPS). Two distinguishable effects of water on oxygen surface exchange are identified. While humidification of the oxidant accelerates the oxygen incorporation in the short-term range, the long-term stability of the cathode decreases substantially. XPS analysis indicates that the accelerated LSC degradation rate under wet conditions originated from an increased change of the surface cation composition.

► Two distinguishable effects of water on oxygen surface exchange of mixed conducting perovskites are identified.
► The experimental results clearly show that at short time the oxygen surface exchange coefficient of La0.6Sr0.4CoO3−δ (LSC) thin films can be increased by the water addition.
► On the other hand, the degradation rate is also accelerated under wet conditions due to increased cation composition changes at the surface.