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Adlayer structure and lattice size effects on catalytic rates predicted from KMC simulations: NO oxidation on Pt(111)

Papanikolaou, KG; Darby, MT; Stamatakis, M; (2018) Adlayer structure and lattice size effects on catalytic rates predicted from KMC simulations: NO oxidation on Pt(111). Journal of Chemical Physics , 149 (18) , Article 184701. 10.1063/1.5048787. Green open access

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Abstract

Repulsive and/or attractive interactions between surface adsorbates have an important effect on the structure of the adsorbate layer and consequently on the rate of heterogeneous catalytic reactions. Thus, developing reaction models that take into account adsorbate-adsorbate interactions is crucial for making accurate predictions of the catalytic rate and surface coverage during reaction. In the present work, we employ kinetic Monte Carlo (KMC) simulation to model the catalytic NO oxidation on Pt (111), adopting a cluster expansion (CE) Hamiltonian approach for treating the aforementioned interactions. We investigate CEs of increasing complexity, ranging from pairwise 1st nearest neighbor (1NN) to long-range and many-body terms. We show that energetics models incorporating solely short-range interactions result in ordered adlayer structures, which are disrupted by anti-phase boundaries and defective regions when the size of the periodic lattice is non-commensurate to the structure of the stable adlayer. We find that O2 dissociates on sites located in these defective regions, which are predominantly responsible for the activity, and the predicted catalytic rate is strongly depended on the lattice size. Such effects are absent when employing non-periodic lattices, whereon the catalytic activity appears more intense on edges/corner sites. Finally, inclusion of long-range interactions in the model Hamiltonian induces relative disorder in the adsorbate layer, which is ascribed to the “softening” of the repulsive interactions between adspecies. Under these circumstances, the distribution of activation energies for O2 dissociation is broader as compared to short-range interaction models and on this basis we explain the disparate catalytic rate predictions when using different CEs.

Type: Article
Title: Adlayer structure and lattice size effects on catalytic rates predicted from KMC simulations: NO oxidation on Pt(111)
Open access status: An open access version is available from UCL Discovery
DOI: 10.1063/1.5048787
Publisher version: https://doi.org/10.1063/1.5048787
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Catalysis, Nanoparticles, Adsorption, Reaction rate constants, Activation energies, Crystallographic defects, Monte Carlo methods, Statistical thermodynamics
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/10060045
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