SOFC LSM:YSZ cathode degradation induced by moisture: An impedance spectroscopy study

The cause of the degradation effect of moisture during operation of LSM cathode based SOFCs has been investigated by means of a detailed impedance characterization on LSM:YSZ composite cathode based SOFCs. Further the role of YSZ as cathode composite material was studied by measurements on SOFCs with a LSM:CGO composite cathode on a CGO interdiffusion barrier layer. It was found that both types of cathodes showed similar electrochemical characteristics towards the presence of moisture during operation. Upon addition and removal of moisture in the fed air the impedance study showed a change in the high frequency cathode arc, which is associated with the charge transport/transfer at the LSM/YSZ interface. On prolonged operation with the presence of moisture an ongoing increase in the high frequency cathode arc resulted in a permanent loss of cathode/electrolyte contact and thus increase in the serial resistance and the high and low frequency cathode arcs. On the basis of these results and reports within literature a mechanism for the effect of moisture was proposed, which attribute to moisture the role of participating in an enhanced removal of manganese from the LSM/YSZ interface and thus eventually a decomposition of LSM.

Research highlights
► The effect of air moisture on LSM:YSZ based SOFCs was characterized by EIS.
► Moisture effect is similar for SOFCs with LSM:YSZ and a LSM:CGO cathode respectively.
► The study indicates a decomposition of LSM at the LSM/YSZ interface due to moisture.
► Enhanced removal of Mn from the LSM/YSZ TPB and interface is attributed to moisture.