In Situ Synchrotron X-ray Spectroscopy of Lanthanum Manganite Solid Oxide Fuel Cell Electrodes

We investigated the underlying physical and chemical causes of the improvement of electrochemical activity of the cathode in solid oxide fuel cells (SOFC) under long term cathodic or anodic polarization, termed 'current conditioning', through in situ X-ray absorption spectroscopy (XAS). The electrodes were powder La0.8Sr0.2MnO3 (LSM) made with spray pyrolysis and thin films of LSM and La0.8Ca0.2MnO3 (LCM) grown by pulsed laser deposition (PLD), all on single crystal Yttria stablized Zirconia (YSZ) substrates. Changes in the XAS of the Mn K, La L3 as well as the Sr K edge for LSM during current conditioning were studied. Our results shows no significant oxidation state changes for the Mn, but instead suggests that the redistribution of cation concentration profiles inside the pervoskite electrode may be the important factor in current conditioning.