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  The puzzle of rapid hydrogen oxidation on Pt(111)

Borodin, D., Schwarzer, M., Hahn, H. W., Fingerhut, J., Wang, Y., Auerbach, D. J., et al. (2021). The puzzle of rapid hydrogen oxidation on Pt(111). Molecular Physics, In Press; e1966533. doi:10.1080/00268976.2021.1966533.

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 Creators:
Borodin, D.1, Author           
Schwarzer, M., Author
Hahn, H. W., Author
Fingerhut, J., Author
Wang, Y., Author
Auerbach, D. J.2, Author           
Guo, H., Author
Schroeder, J.1, Author           
Kitsopoulos, T. N.2, Author           
Wodtke, A. M.2, Author           
Affiliations:
1Department of Dynamics at Surfaces, MPI for Biophysical Chemistry, Max Planck Society, ou_persistent22              
2Department of Dynamics at Surfaces, MPI for biophysical chemistry, Max Planck Society, ou_578600              

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Free keywords: Heterogeneous catalysis; Hydrogen oxidation; Platinum; Molecular beams; Velocity resolved kinetics
 Abstract: We have known for over 200 years that hydrogen undergoes rapid oxidation to water on Pt catalysts; yet the reaction mechanism remains unclear. Here, we report high temporal resolution measurements of the production rate of H2O from hydrogen oxidation catalysed by a Pt (111) single crystal surface with a known concentration of adsorbed oxygen atoms and a step density of approximately 0.002 ML. We obtain two rate constants describing the rise, and fall of the reaction rate between 350 and 470 K and compare our observations to modern ab initio predictions of the reaction rates in surface chemistry. Remarkably, a mechanism based on a standard set of elementary reaction steps with energies and barrier heights obtained from Density Functional Theory (DFT), predicts a rate that is four orders of magnitude smaller than observed experimentally. Furthermore, the theoretically predicted reaction rate follows first-order kinetics, whereas the experimental observations clearly show a second-order reaction. The theoretical predictions are robust – six different exchange–correlation functionals lead to similar predictions. We suggest that the reason for these disagreements is that the active sites of the catalyst and the associated elementary reactions have, so far, not been properly identified.

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Language(s): eng - English
 Dates: 2021-08-20
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1080/00268976.2021.1966533
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Title: Molecular Physics
Source Genre: Journal
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Pages: - Volume / Issue: - Sequence Number: In Press; e1966533 Start / End Page: - Identifier: -