A detailed velocity-resolved kinetics study of NH3 thermal desorption rates from p(2 × 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 × 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 × 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 × 2) O/Pt(111), which indicates the importance of dispersion interactions for both systems.
Bibliographical noteFunding Information:
D.B., J.F., A.K., and T.N.K. acknowledge support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. ). O.G. acknowledges financial support by the Spanish Ministerio de Ciencia e Innovación [Grant no. PID2019-107396GB-I00/AEI/10.13039/501100011033]. I.R. gratefully acknowledges the support by Israel Science Foundation, ISF (grant No. 2187/19), and by the Open University of Israel Research Authority (grant No. 31044). M.S. thanks the BENCh graduate school, funded by the DFG (389479699/GRK2455).
Open access funded by Max Planck Society.
© 2022 The Authors. Published by American Chemical Society.