TY - JOUR

T1 - Surface and Defect Chemistry of Porous La0.6Sr0.4FeO3−δ Electrodes on Polarized Three-Electrode Cells

AU - Nenning, Andreas

AU - Reuter, Stefan

AU - Schlesinger, Richard

AU - Summerer, Harald

AU - Ramehsan, Raffael

AU - Lindenthal, Lorenz

AU - Holzmann, Manuel

AU - Huber, Tobias Martin

AU - Rameshan, Christoph

AU - Fleig, Jürgen

AU - Opitz, Alexander Karl

PY - 2022/9/20

Y1 - 2022/9/20

N2 - Even though solid oxide fuel/electrolysis cells (SOFC/SOEC) are already commercially available, the effect of electrochemical polarization on the electrochemical properties and overpotentials of individual electrodes is largely unexplored. This is partly due to difficulties in separating anode and cathode impedance features and overpotentials of operating fuel cells. For this, we present a novel three-electrode geometry to measure single-electrode impedance spectra and overpotentials in solid oxide cells. With this new design, we characterise polarised porous La0.6Sr0.4FeO3−δ (LSF) electrodes by simultaneous impedance spectroscopy and ambient pressure XPS measurements. With physically justified equivalent circuit models, we can show how the overpotential-dependent changes in the impedance and XPS spectra are related to oxygen vacancy and electronic point defect concentrations, which deterimine the electrochemical properties. The results are overall in very good agreement with the key findings of several previous studies on the bulk defect chemistry and surface chemistry of LSF. They show for example the exsolution of Fe0 particles during cathodic polarisation in H2 + H2O atmosphere that decrease the polarization resistance by roughly one order of magnitude.

AB - Even though solid oxide fuel/electrolysis cells (SOFC/SOEC) are already commercially available, the effect of electrochemical polarization on the electrochemical properties and overpotentials of individual electrodes is largely unexplored. This is partly due to difficulties in separating anode and cathode impedance features and overpotentials of operating fuel cells. For this, we present a novel three-electrode geometry to measure single-electrode impedance spectra and overpotentials in solid oxide cells. With this new design, we characterise polarised porous La0.6Sr0.4FeO3−δ (LSF) electrodes by simultaneous impedance spectroscopy and ambient pressure XPS measurements. With physically justified equivalent circuit models, we can show how the overpotential-dependent changes in the impedance and XPS spectra are related to oxygen vacancy and electronic point defect concentrations, which deterimine the electrochemical properties. The results are overall in very good agreement with the key findings of several previous studies on the bulk defect chemistry and surface chemistry of LSF. They show for example the exsolution of Fe0 particles during cathodic polarisation in H2 + H2O atmosphere that decrease the polarization resistance by roughly one order of magnitude.

U2 - 10.1149/1945-7111/ac908b

DO - 10.1149/1945-7111/ac908b

M3 - Article

VL - 169.2022

JO - Journal of the Electrochemical Society

JF - Journal of the Electrochemical Society

SN - 0013-4651

IS - 9

M1 - 094508

ER -