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When More Is Less: Nonmonotonic Trends in Adsorption on Clusters in Alloy Surfaces

preprint
revised on 14.08.2020 and posted on 17.08.2020 by Abigale Monasterial, Calla Hinderks, Songkun Viriyavaree, Matthew Montemore
Single-atom alloys can be effective catalysts and have been compared to supported single-atom catalysts. To rationally design single-atom alloys and other surfaces with localized ensembles, it is crucial to understand variations in reactivity when varying the dopant and the ensemble size. Here, we examined hydrogen adsorption on surfaces embedded with localized clusters and discovered general trends. Counterintuitively, increasing the amount of a more reactive metal sometimes makes a surface site less reactive. This behavior is due to the hybridization and splitting of narrow peaks in the electronic density of states of many of these surfaces, making them analogous to free-standing nanoclusters. When a single-atom alloy has a peak just below the Fermi energy, the corresponding two-dopant cluster often has weaker adsorption than the single-atom alloy due to splitting of this peak across the Fermi energy. Further, single-atom alloys have qualitatively different behavior than larger ensembles. Specifically, the adsorption energy is a U-shaped function of the dopant’s group for single atom alloys. Additionally, adsorption energies on single atom alloys correlate more strongly with the dopant’s p-band center than the d-band center.

Funding

NSF DMR-1852274

Louisiana Board of Regents LEQSF(2019-22)-RD-A-20

History

Email Address of Submitting Author

mmontemore@tulane.edu

Institution

Tulane University

Country

United States

ORCID For Submitting Author

0000-0002-4157-1745

Declaration of Conflict of Interest

No conflict of interest

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