Heterogeneous catalysis of photocatalytically active perovskite nanoparticles like LaFeO3 occurs by the interaction of molecules with active sites of the particle surface. While the crystalline core is resolved using conventional X-ray diffraction (XRD), structural changes of the boundary layer during catalytic activity are accessible by In situ X-ray spectroscopy (XAS) .
Since nanoparticles have a high ratio of surface to volume atoms, a large fraction of the measured signal originates from the surface. By Reverse Monte Carlo (RMC) analysis, pair distribution functions can be retrieved from XAS measurements which contain the structural evolution and information of the local structure of the particle and its surface.
To constrain the RMC model, it is important that the initial single particle model closely represents measured particles. Since in situ XAS is an ensemble measurement over thousands of individual nanoparticles, the measured nanoparticles must be phase pure, monodisperse, very small, highly crystalline and dispersible. The requirements of colloidal perovskite photocatalytic nanoparticles for in situ probing of the structure-activity-relationships are discussed and first ex situ measurements using RMC analysis will be presented.
 Sandmann, A., Kompch, A., Mackert, V., Liebscher, C. H. & Winterer, M. Interaction of L-Cysteine with ZnO: Structure, Surface Chemistry, and Optical Properties. Langmuir : the ACS journal of surfaces and colloids 31, 5701–5711 (2015).
This work is supported by the German Research Foundation (DFG) through the Collaborative Research Center 247, Projekt B01. The authors gratefully acknowledge the provision of XAS beamtime at Diamond and the Advanced Photon Source and support by Fred Mosselmans and Sungsik Lee at beamlines I20 and 12-BM-B.
5:00 PM–7:00 PM Apr 23, 2019 (US - Arizona)
PCC North, 300 Level, Exhibit Hall C-E