Steric Hindrance of NH3 Diffusion on Pt(111) by Co-Adsorbed O-Atoms
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Date
2022Author
Borodin, Dmitriy
Galparsoro Larraza, Oihana
Rahinov, Igor
Fingerhut, Jan
Schwarzer, Michael
Horandl, Stefan
Auerbach, Daniel J.
Kandratsenka, Alexander
Schwarzer, Dirk
Kitsopoulos, Theofanis N.
Wodtke, Alec M.
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Journal of the American Chemical Society 144(47) : 21791-21799 (2022)
Abstract
A detailed velocity-resolved kinetics study of NH3 thermal desorption rates from p(2 x 2) O/Pt(111) is presented. We find a large reduction in the NH3 desorption rate due to adsorption of O-atoms on Pt(111). A physical model describing the interactions between adsorbed NH3 and O-atoms explains these observations. By fitting the model to the derived desorption rate constants, we find an NH3 stabilization on p(2 x 2) O/Pt(111) of 0.147-0.014 +0.023 eV compared to Pt(111) and a rotational barrier of 0.084-0.022 +0.049 eV, which is not present on Pt(111). The model also quantitatively predicts the steric hindrance of NH3 diffusion on Pt(111) due to co-adsorbed O-atoms. The derived diffusion barrier of NH3 on p(2 x 2) O/Pt(111) is 1.10-0.13 +0.22 eV, which is 0.39-0.14 +0.22 eV higher than that on pristine Pt(111). We find that Perdew Burke Ernzerhof (PBE) and revised Perdew Burke Ernzerhof (RPBE) exchange-correlation functionals are unable to reproduce the experimentally observed NH3-O adsorbate-adsorbate interactions and NH3 binding energies at Pt(111) and p(2 x 2) O/Pt(111), which indicates the importance of dispersion interactions for both systems.