In operando Raman spectroscopy as a tool for investigation of solid oxide electrodes

Solid oxide electrodes are important in a number of technologies including solid oxide fuel cells, solid oxide electrolysis cells, gas sensors and electrochemical gas purification. The electrodes operate at elevated temperatures (300-900 °C), while they are subjected to gas flow and electrical polarisation. Conventionally, the solid oxide electrodes have been studied by electrochemical techniques during operation, and then analyzed post-mortem using electron microscopy, elemental analyses etc. However, accurate interpretation of the electrochemical response from the electrodes requires careful in situ monitoring with techniques capable of resolving specific chemical changes that occur in real time. For instance Raman spectroscopy may yield insight into the presence of segregated oxide species or contaminating impurities on the electrodes during operation. In the work presented here, Raman spectroscopy has been applied in operando to study electrochemical gas purification that results from electrochemical reduction of NOx, on lanthanum strontium manganite (LSM) electrodes. One LSM electrode was modified with Ba, and in operando Raman studies revealed the presence of a new oxide phase that showed a strong dependence on the applied electrical potential. These results illustrate how in operando Raman spectroscopy expands our understanding of why Ba-modified LSM electrodes show higher NOx conversion during electrochemical gas purification compared to un-modified LSM electrodes. Due to the great potential of combining in operando Raman spectroscopy with electrochemical characterisation, DTU Energy Conversion decided in 2014 to invest in a set-up dedicated to this purpose, At the end of the talk a short description will be given of this set-up, and the future plans will be described for combined in operando Raman spectroscopy and electrochemical characterisation at DTU Energy Conversion.