Lee Hsun Lecture Series

Topic: Heterogeneous Catalysts – The Presence of Local Structures and their Temporal Evolution

Speaker: Dr. Thomas Lunkenbein

         Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany

Abstract:

A heterogeneous catalyst is a metastable material. Similar to other solids heterogeneous catalysts exhibit a rich defect chemistry in their bulk and surface structures, which can modulate their catalytic performance.[1] However, for prospective rational catalyst design, which also includes a sufficient long-term stability, the impact of such local structures on the catalytic turnover has to be fully understood. To achieve this goal an unprecedented insight into these structures on the local scale is required.

Although information on the bulk and surface structure can be obtained by integral methods, such as X-ray diffraction and/or X-ray photoelectron spectroscopy, important local deviations from the ideal structure may be overlooked. Nowadays, local insights can be obtained by modern transmission electron microscopes (TEM). Recent developments in the field of electron microscopy have rendered this technique as the tool to locally describe the nano- and mesoscale of heterogeneous catalysts also under working conditions.[2]

In this lecture the local complexity in structure and composition of different heterogeneous catalysts will be addressed.[3] It will be shown how heterogeneous a macroscopic homogeneous sample can be. In addition, the temporal evolution of such local structures during the catalytic reaction was tracked by ex situ, quasi in situ, and operando electron microscopy techniques implying the occurrence of structural and morphological changes on the atomic and mesoscale.[4]

References

[1] H. S. Taylor, Proceedings of the Royal Society of London Series a-Containing Papers of a Mathematical and Physical Character 1925, 108, 105-111.

[2] S. B. Vendelbo, C. F. Elkjaer, H. Falsig, I. Puspitasari, P. Dona, L. Mele, B. Morana, B. J. Nelissen, R. van Rijn, J. F. Creemer, P. J. Kooyman, S. Helveg, Nature Materials 2014, 13, 884-890.

[3] L. Masliuk, M. Heggen, J. Noack, F. Girgsdies, A. Trunschke, K. E. Hermann, M. G. Willinger, R. Schlogl, T. Lunkenbein, Journal of Physical Chemistry C 2017, 121, 24093-24103; T. Lunkenbein, F. Girgsdies, A. Wernbacher, J. Noack, G. Auffermann, A. Yasuhara, A. Klein-Hoffmann, W. Ueda, M. Eichelbaum, A. Trunschke, R. Schlogl, M. G. Willinger, Angewandte Chemie-International Edition 2015, 54, 6828-6831; T. Lunkenbein, J. Schumann, M. Behrens, R. Schlogl, M. G. Willinger, Angewandte Chemie-International Edition 2015, 54, 4544-4548.

[4] L. Masliuk, M. Swoboda, G. Algara-Siller, R. Schlogl, T. Lunkenbein, Ultramicroscopy 2018, 195, 121-128; T. Lunkenbein, F. Girgsdies, T. Kandemir, N. Thomas, M. Behrens, R. Schlogl, E. Frei, Angewandte Chemie-International Edition 2016, 55, 12708-12712.