2015-06-11 - the 25th Rudolf Brdička Memorial Lecture (June 11, 2015)
The Institute has organized since 1991 annual Rudolf Brdička Memorial Lectures to commemorate the founder and first director of one of the constituent parts of the present Institute.
The 25th Annual Rudolf Brdička Lecture was held on June 11, 2015 at 14:00 in Brdička lecture hall of the Institute.
Institute of Applied Physics, TU Wien, Vienna, Austria diebold
iap.tuwien.ac.at (diebold[at]iap[dot]tuwien[dot]ac[dot]at)
With the advent of Scanning Tunneling Microscopy (STM) a dream has come true in surface chemistry: to directly watch how a single molecule adsorbs on a surface and undergoes a chemical transformation. Combined with first-principles theory, such measurements allow identifying specific surface sites, as well as reaction processes and mechanisms that are at the heart of heterogeneous, photo- and electrocatalysis.
In the talk I will give an overview of the insights gained from such combined STM/DFT investigations. I will mainly focus on TiO2, the prototypical system for surface science experiments on metal oxides; technologically important, yet fundamentally challenging materials. The semiconducting properties of TiO2 (and the fact that it is cheap, stable, readily available, and can be produced in a variety of nanostructures) make it popular in well-established fields, such as photocatalysis, and emerging technologies, such as memristive switching.
To be meaningful, surface science studies are best conducted on single-crystals in ultrahigh vacuum, although recent STM studies in aqueous solutions point towards the potential of using this technique in other environments as well. The surface geometrical and electronic structures of various facets and polymorphs of TiO2 are now well understood. An important aspect are surface defects, in particular O vacancies that form easily in reducible metal oxides. Such defects can be judiciously created by electron bombardment, and with STM one can inspect individual defects and even manipulate them. I will discuss adsorption, diffusion and photo-induced processes for various molecules. The results will be compared with other systems systems, e.g. iron oxides, where vacancies in the cation sublattice influence surface properties in a profound way.
References
U. Diebold, “The Surface Science of Titanium Dioxide”, Surface Science Reports, 48 (2003) 53 – 229
Y. He, A. Tilocca, O. Dulub, A. Selloni, and U. Diebold, “Local ordering and electronic signatures of submonolayer water on anatase TiO2(101)” Nature Materials 8 (2009) 585 - 589
M. Setvin, U. Aschauer, Ph. Scheiber, M. Schmid, A. Selloni, U. Diebold “Reaction of O2 with Subsurface Oxygen Vacancies on TiO2 Anatase (101)” Science, 341 (2013) 988
R. Bliem, E. McDermott, P. Ferstl, M. Setvin, O. Gamba, M. A. Schneider, M. Schmid, U. Diebold, P. Blaha, L. Hammer, G. S. Parkinson “Subsurface Cation Vacancy Stabilization of the Magnetite (001) Surface” Science, 346 (2014) 1215
