March 2012Sr-doped LaMnO3 is the commonly used cathode material for solid oxide fuel cells. During cell operation significant changes of cation surface concentrations occur resulting in crucial effect on the cell performance. The presented experiment focusses on in situ observation of surface composition changes induced by electrochemical polarization applying spatially resolving surface analysis techniques like XPS, SPEM and SIMS and their influence on the cell performance. The figure shows SPEM images of a LSCrM surface after cathodic (left) and anodic polarization (right). The anodically polarized electrode shows small surface areas with enhanced strontium concentrations. During the cathodic polarization the strontium islands disappear and a re-segregation of Sr onto the LSCrM surface occurs with applied anodic bias. The formation of inhibiting SrO surface species under anodic polarization deactivates the electrode whereas the incorporation of the SrO surface layer into the LSM lattice under anodic polarization facilitates the oxygen surface exchange reaction, resulting in an electrochemical activation of the cell. Further information about the electrochemical driven surface segregation processes and their influence on the cell performance of perovskite electrodes for SOFCs offers the following, recently published article: A.-K. Huber, M. Falk, M. Rohnke, B. Luerssen, L. Gregoratti, A. Matteo, J. Janek, In situ study of electrochemical activation and surface segregation of the SOFC electrode material La0.75Sr0.25Cr0.5Mn0.5O3±δ, Phys. Chem. Chem. Phys., 2012, 14, 751–758. (Picture submitted by Anne-Katrin Huber.) https://www.uni-giessen.de/en/faculties/f08/departments/physchem/janek/gallerypotm/gallery-of-pictures-from-2012/PoM0312a/viewhttps://www.uni-giessen.de/@@site-logo/logo.png
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March 2012
Sr-doped LaMnO3 is the commonly used cathode material for solid oxide fuel cells. During cell operation significant changes of cation surface concentrations occur resulting in crucial effect on the cell performance. The presented experiment focusses on in situ observation of surface composition changes induced by electrochemical polarization applying spatially resolving surface analysis techniques like XPS, SPEM and SIMS and their influence on the cell performance. The figure shows SPEM images of a LSCrM surface after cathodic (left) and anodic polarization (right). The anodically polarized electrode shows small surface areas with enhanced strontium concentrations. During the cathodic polarization the strontium islands disappear and a re-segregation of Sr onto the LSCrM surface occurs with applied anodic bias. The formation of inhibiting SrO surface species under anodic polarization deactivates the electrode whereas the incorporation of the SrO surface layer into the LSM lattice under anodic polarization facilitates the oxygen surface exchange reaction, resulting in an electrochemical activation of the cell. Further information about the electrochemical driven surface segregation processes and their influence on the cell performance of perovskite electrodes for SOFCs offers the following, recently published article: A.-K. Huber, M. Falk, M. Rohnke, B. Luerssen, L. Gregoratti, A. Matteo, J. Janek, In situ study of electrochemical activation and surface segregation of the SOFC electrode material La0.75Sr0.25Cr0.5Mn0.5O3±δ, Phys. Chem. Chem. Phys., 2012, 14, 751–758. (Picture submitted by Anne-Katrin Huber.)
