TY - JOUR

T1 - The Chemical Evolution of the La0.6Sr0.4CoO3−Δ Surface Under SOFC Operating Conditions and Its Implications for Electrochemical Oxygen Exchange Activity

AU - Opitz, Alexander Karl

AU - Rameshan, Christoph

AU - Kubicek, Markus

AU - Rupp, Ghislain M.

AU - Nenning, Andreas

AU - Götsch, Thomas

AU - Blume, Raoul

AU - Hävecker, Michael

AU - Knop-Gericke, Axel

AU - Rupprechter, Günther

AU - Klötzer, Bernhard

AU - Fleig, Jürgen

N1 - Publisher Copyright: © 2018, The Author(s).

PY - 2018/12/1

Y1 - 2018/12/1

N2 - Owing to its extraordinary high activity for catalysing the oxygen exchange reaction, strontium doped LaCoO3 (LSC) is one of the most promising materials for solid oxide fuel cell (SOFC) cathodes. However, under SOFC operating conditions this material suffers from performance degradation. This loss of electrochemical activity has been extensively studied in the past and an accumulation of strontium at the LSC surface has been shown to be responsible for most of the degradation effects. The present study sheds further light onto LSC surface changes also occurring under SOFC operating conditions. In-situ near ambient pressure X-ray photoelectron spectroscopy measurements were conducted at temperatures between 400 and 790 °C. Simultaneously, electrochemical impedance measurements were performed to characterise the catalytic activity of the LSC electrode surface for O2 reduction. This combination allowed a correlation of the loss in electro-catalytic activity with the appearance of an additional La-containing Sr-oxide species at the LSC surface. This additional Sr-oxide species preferentially covers electrochemically active Co sites at the surface, and thus very effectively decreases the oxygen exchange performance of LSC. Formation of precipitates, in contrast, was found to play a less important role for the electrochemical degradation of LSC.

AB - Owing to its extraordinary high activity for catalysing the oxygen exchange reaction, strontium doped LaCoO3 (LSC) is one of the most promising materials for solid oxide fuel cell (SOFC) cathodes. However, under SOFC operating conditions this material suffers from performance degradation. This loss of electrochemical activity has been extensively studied in the past and an accumulation of strontium at the LSC surface has been shown to be responsible for most of the degradation effects. The present study sheds further light onto LSC surface changes also occurring under SOFC operating conditions. In-situ near ambient pressure X-ray photoelectron spectroscopy measurements were conducted at temperatures between 400 and 790 °C. Simultaneously, electrochemical impedance measurements were performed to characterise the catalytic activity of the LSC electrode surface for O2 reduction. This combination allowed a correlation of the loss in electro-catalytic activity with the appearance of an additional La-containing Sr-oxide species at the LSC surface. This additional Sr-oxide species preferentially covers electrochemically active Co sites at the surface, and thus very effectively decreases the oxygen exchange performance of LSC. Formation of precipitates, in contrast, was found to play a less important role for the electrochemical degradation of LSC.

KW - Impedance spectroscopy

KW - NAP-XPS

KW - Oxygen reduction

KW - Perovskite-type electrode

KW - SOFC cathode

KW - Strontium segregation

UR - http://www.scopus.com/inward/record.url?scp=85055680288&partnerID=8YFLogxK

U2 - 10.1007/s11244-018-1068-1

DO - 10.1007/s11244-018-1068-1

M3 - Article

AN - SCOPUS:85055680288

VL - 61.2018

SP - 2129

EP - 2141

JO - Topics in catalysis

JF - Topics in catalysis

SN - 1022-5528

IS - 20

ER -