Passivation and activation of La_0.6Sr_0.4FeO₃ thin film electrodes

The oxygen exchange activity of thin dense La_0.6Sr_0.4FeO₃ electrodes prepared by pulsed laser deposition was investigated by electrochemical impedance spectroscopy and electrical conductivity relaxation below 600 °C. The value of the surface exchange coefficient (k_chem) measured at 491 °C decreased from an initial 4.4 × 10^-6 cm s^-1 to 1.7 × 10^-7 cm s^-1 after aging for 7 days. The rapid decrease in the oxygen exchange rate was accompanied by the increase in the surface concentration of 'non-lattice strontium' detected by X-ray photoelectron spectroscopy. Subsequent electrochemical tests over 40 days showed that the electrode performance could be recovered by rinsing the passivated electrode in deionized water. Repeated treatments eventually also led to improved stability of electrochemical performance.