Busse, P.; Yin, Z.; Mierwaldt, D.; Scholz, J.; Kressdorf, B.; Glaser, L.; Miedema, P.; Rothkirch, A.; Viefhaus, J.; Jooss, C.; Techert, S.; Risch, M.: Probing the Surface of La0.6Sr0.4MnO3 in Water Vapor by In Situ Photon-In / Photon-Out Spectroscopy. The Journal of Physical Chemistry C 124 (2020), p. 7893-7902
10.1021/acs.jpcc.0c00840
Open Accesn Version (available 01.03.2021)

Abstract:
Resonant inelastic X-ray scattering (RIXS) is a promising method for elucidating detailed electronic structure of materials in a broad range of chemical and physical applications. Here, we use the fine fluorescence energy resolution of a RIXS spectrometer to obtain various proxies of the Mn-L edge X-ray absorption spectra (XAS) of the perovskite La0.6Sr0.4MnO3 (LSMO) as a model catalyst for the oxygen evolution reaction (OER) and evaluate the suitability for in situ surface studies of this electrocatalyst. We conclude that the inverse partial fluorescence yield (IPFY) of the O 2p-1s transition and the partial fluorescence yield of the 3s-2p transition (3s-PFY) are most suitable for determining changes at the surface of the perovskite, because distortions at grazing incidence measurements are low. In particular, the negligible angular dependence of the 3s-PFY spectra can be perfectly simulated using a fluorescence model in the thin sample limit which is justified by low reabsorption of 3s-photons. Remarkably, the 3s-PFY reveals an influence of water vapor on the electronic reconstruction of the LSMO surface. Thus, our work paves the road for quantitative distortion-free X-ray spectroscopy of transition metal oxide surfaces under in situ conditions, which is needed to understand fundamental chemical processes such as corrosion and catalysis.