The oxygen exchange kinetics and the surface chemistry of epitaxially grown, dense La0.6Sr0.4CoO3−δ (LSC) thin films in three different orientations, (001), (110), and (111), were investigated by means of in situ impedance spectroscopy during pulsed laser deposition (i-PLD) and near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). i-PLD measurements showed that pristine LSC surfaces exhibit very fast surface exchange kinetics but revealed no significant differences between the specific orientations. However, as soon as the surfaces were in contact with acidic, gaseous impurities, such as S-containing compounds in nominally pure measurement atmospheres, NAP-XPS measurements revealed that the (001) orientation is substantially more susceptible to the formation of sulfate adsorbates and a concomitant performance decrease. This result is further substantiated by a stronger increase of the work function on (001)-oriented LSC surfaces upon sulfate adsorbate formation and by a faster performance degradation of these surfaces in ex situ measurement setups. This phenomenon has potentially gone unnoticed in the discussion of the interplay between the crystal orientation and the oxygen exchange kinetics and might have far-reaching implications for real solid oxide cell electrodes, where porous materials exhibit a wide variety of differently oriented and reconstructed surfaces.
Bibliographische NotizFunding Information:
Open Access is funded by the Austrian Science Fund (FWF).
The authors acknowledge financial support and open access funding provided by the Austrian Science Fund Projects P31654-N37 and P31165-N37. M.S. was also partly supported by the Competence CEST in the framework of the COMET scheme of the Austrian Research Promotion Agency (Project 865864). This research has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation programme, Grant Agreement 755744/ERC─Starting Grant TUCAS.
© 2023 The Authors. Published by American Chemical Society.