Operando Catalysis Studies from Model Systems to Real Catalysts

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. 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 can be studied under ambient pressure catalytic reaction conditions. In the first part of my talk I will present different ensemble averaging synchrotron radiation based x-ray diffraction schemes. They deliver quantitative information on the nanoparticle size, shape and facet surface structures under operando reaction conditions for CO oxidation using high resolution reciprocal space mapping and high energy x-ray diffraction [1-4]. In the second part I will focus on experiments overcoming the ensemble average by single nanoparticle imaging and I will discuss future possibilities exploiting the high coherence of high energy photons available at fourth generation synchrotron radiation sources [5].<br/><br/><b>References:</b><br/><br/>[1] P. Nolte, A. Stierle, N. Y. Jin-Phillipp, N. Kasper, T. U. Schulli, H. Dosch, Science 321, 1654-1658 (2008).<br/>[2] U. Hejral, D. Franz, S. Volkov, S. Francoual, J. Strempfer, and A. Stierle, Phys. Rev. Lett. 120, 126101 (2018).<br/>[3] J. Gustafson, M. Shipilin, C. Zhang, A. Stierle, U. Hejral, U. Ruett, O. Gutowski, P.-A. Carlsson, M. Skoglundh, E. Lundgren, Science 343, 758 (2014).<br/>[4] U. Hejral, P. Müller, O. Balmes, D. Pontoni, A. Stierle, Nature Communications 7, 10964 (2016).<br/>[5] Y. Y. Kim, T. F. Keller, T. J. Goncalves, M. Abuin, H. Runge, L. Gelisio, J. Carnis, V. Vonk, P. N. Plessow, I. A. Vartaniants, A. Stierle, Sci. Adv. 7 eabh0757 (2021).