Atomic-Scale Explanation of O2 Activation at the Au-TiO2 Interface

Siemer, N. and Lüken, A. and Zalibera, M. and Frenzel, J. and Muñoz-Santiburcio, D. and Savitsky, A. and Lubitz, W. and Muhler, M. and Marx, D. and Strunk, J.

Volume: 140 Pages: 18082-18092
DOI: 10.1021/jacs.8b10929
Published: 2018

By a combination of electron paramagnetic resonance spectroscopy, finite-temperature ab initio simulations, and electronic structure analyses, the activation of molecular dioxygen at the interface of gold nanoparticles and titania in Au/TiO2 catalysts is explained at the atomic scale by tracing processes down to the molecular orbital picture. Direct evidence is provided that excess electrons in TiO2, for example created by photoexcitation of the semiconductor, migrate to the gold particles and from there to oxygen molecules adsorbed at gold/titania perimeter sites. Superoxide species are formed more efficiently in this way than on the bare TiO2 surface. This catalytic effect of the gold nanoparticles is attributed to a weakening of the internal O-O bond, leading to a preferential splitting of the molecule at shorter bond lengths together with a 70% decrease of the dissociation free energy barrier compared to the non-catalyzed case on bare TiO2. The findings are an important step forward in the clarification of the role of gold in (photo)catalytic processes. © 2018 American Chemical Society.

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