In-situ X-ray Diffraction Studies of Nanoparticle Model Catalysts
by
Prof.Dr. Andreas Stierle(DESY NanoLab and University of Hamburg)
→
Europe/Stockholm
FB55
FB55
Description
The atomic structure determination of nano-objects with dimensions in the sub-100 nm regime is a formidable task for today’s diffraction, imaging and scanning probe techniques. Such a detailed structural and compositional analysis is mandatory for a correlation with the nano-object’s functionality e.g. as heterogeneous catalysts, magnetic storage material or light emitting device. In conventional x-ray diffraction experiments on powder samples the structural analysis is hampered by a random nanoparticle orientation and often by background scattering from the supporting material. We have therefore focused on the development of model systems based on epitaxial metal nanoparticles on single crystal oxide supports, which are stable under ambient pressure catalytic reaction conditions. Here I will present different ensemble averaging in-situ synchrotron radiation based x-ray diffraction schemes delivering quantitative information on the nanoparticle size, shape and facet surface structures under varying gas surroundings:
First I will discuss high resolution reciprocal space mapping from epitaxial Rh, Pd and Pt-Rh nanoparticles under oxidizing and reducing conditions, as well as during CO oxidation at near atmospheric pressures [1]. As a second approach I will present a combinatorial high energy x-ray diffraction scheme (85 keV photon energy) allowing a systematical screening of particle size or composition under identical reaction conditions, which we used to follow the CO oxidation induced sintering process of PtRh nanoparticles as a function of their composition [2]. Finally, I will demonstrate how graphene templated growth of nanoparticles with diameter < 2 nm opens the door for x- ray diffraction experiments with high crystallographic precision and monitoring of nanoparticle / gas molecule interactions [3,4].
[1] P. Nolte, A. Stierle, N. Y. Jin-Phillipp, N. Kasper, T. U. Schulli, H. Dosch, Science 321, 1654-1658 (2008).
[2] U. Hejral, P. Müller, O. Balmes, D. Pontoni, A. Stierle, Nature Communications 7, 10964 (2016).
[3] D. Franz, S. Runte, C. Busse, S. Schumacher, T. Gerber, T. Michely, M. Mantilla, V. Kilic, J. Zegenhagen, und A. Stierle, Phys. Rev. Lett. 110, 065503 (2013).
[4] D. Franz, N. Blanc, J. Coraux, G. Renaud, S. Runte, T. Gerber, C. Busse, T. Michely, P. Feibelman, U. Hejral, A. Stierle, Phys. Rev. B 93, 4 (2016).
