Observing surface reactions under ambient conditions
From fine chemical synthesis over combustion control to electrode design – the majority of chemical reactions rely on catalysts to improve energy and material efficiency. Yet, the atomic-scale processes underlying a catalytic reaction at elevated pressures are far less well-understood than one might expect. Indeed, the successful optimization of industrial catalysts is typically achieved by ‘trial and error’. If we precisely understood the correlation between catalyst dynamics and activity, we could instead design stable, yet intrinsically dynamic (i.e. structurally fluxional) catalysts, drastically reduce our waste of noble metals by using only the most active particles and replace rare and toxic materials.
Our approach to tackle this challenge lies in a fundamental and systematic investigation of heterogeneous catalysis in action. Our aim is to map the pressure and temperature range in which supported particle catalysts are stable, and correlate particle size and support morphology with dynamics and stability. To this purpose, we perform surface dynamics studies by video-rate scanning tunneling microscopy (FastSTM) under near ambient pressure (NAP) conditions on oxide-supported size-selected clusters. Video-rate NAP-STM allows us to observe catalyst dynamics such as sintering, adsorbate spillover onto the support, dynamic structural fluxionality of clusters and support roughening as a function of reactant partial pressure and temperature. By studying size-selected clusters, defined to the exact number of atoms, under realistic reaction conditions, we aim to tune their reactivity by controlling dynamics and stability on structurally and electronically optimized oxide supports. X-ray photoelectron spectroscopy under the same conditions (NAP-XPS) supplies complementary information about chemical changes occurring in cluster and support, which we typically perform at beamlines at the ALS, Lawrence Berkeley Lab and European synchrotrons. We hope that the knowledge gained by our fundamental investigations will contribute to the targeted design of more active and efficient catalysts for specific applications.
We closely collaborate with the VT-STM group at the Chair of Physical Chemistry.
S. Kaiser, F. Maleki, K. Zhang, W. Harbich, U. Heiz, S. Tosoni, B. A. J. Lechner, G. Pacchioni, F. Esch, "Cluster Catalysis with Lattice Oxygen: Tracing Oxygen Transport from a Magnetite (001) Support onto Small Pt Clusters", ACS Catal. 11, 9519-9529 (2021).
B. Arndt, B. A. J. Lechner, A. Bourgund, E. Grånäs, M. Creutzburg, K. Krausert, J. Hulva, G. S. Parkinson, M. Schmid, V. Vonk, F. Esch, A. Stierle, “Order-disorder phase transition of the subsurface cation vacancy reconstruction on Fe3O4(001)”, Phys. Chem. Chem. Phys., 22, 8336-8343 (2020)
A. Bourgund, B. A. J. Lechner, M. Meier, C. Franchini, G. S. Parkinson, U. Heiz, F. Esch, “Influence of local defects on the dynamics of O-H bond breaking and formation on a magnetite surface”, J. Phys. Chem. C, 123, 19742-19747 (2019).
C. Dri, M. Panighel, D. Tiemann, L. L. Patera, G. Troiano, Y. Fukamori, F. Knoller, B. A. J. Lechner, G. Cautero, D. Giuressi, G. Comelli, J. Fraxedas, C. Africh, F. Esch, “The new FAST module: A portable and transparent add-on module for time-resolved investigations with commercial scanning probe microscopes”, Ultramicroscopy, 205, 49-56 (2019).
B.A.J. Lechner, F. Knoller, A. Bourgund, U. Heiz, F. Esch, “A microscopy approach to investigating the energetics of small supported metal clusters”, J. Phys. Chem. C, 122, 22569-22576 (2018).
B. Zugic, L. Wang, C. Heine, D. N. Zakharov, B. A. J. Lechner, E. A. Stach, J. Biener, M. Salmeron, R. J. Madix, C. M. Friend, “Dynamic restructuring drives catalytic activity on nanoporous gold-silver alloy catalysts”, Nat. Mater. 16, 558-564 (2017).
B. A. J. Lechner, X. Feng, P. J. Feibelman, J. I. Cerdà, M. Salmeron, “Scanning tunneling microscopy study of the structure and interaction between carbon monoxide and hydrogen on the Ru(0001) surface”, J. Phys. Chem. B 122, 649 (2017).
P. Rotter, B. A. J. Lechner, A. Morherr, D. M. Chisnall, D. Ward, A. P. Jardine, J. Ellis, W. Allison, B. Eckhardt, G. Witte, “Coupling between diffusion and orientation of pentacene molecules on an organic surface”, Nat. Mater. 15, 397-400 (2016).
S. Maier, B. A. J. Lechner, G. A. Somorjai, M. Salmeron, “Growth and structure of the first layers of ice on Ru(0001) and Pt(111)”, J. Am. Chem. Soc. 138, 3145-3151 (2016).
B. A. J. Lechner, H. Hedgeland, J. Ellis, W. Allison, M. Sacchi, S. J. Jenkins, B. J. Hinch, “Quantum influences in the diffusive motion of pyrrole/Cu(111)”, Angew. Chem. Int. Ed. 52, 5085-5088 (2013).