The catalytic activity of metals supported on oxides depends on their charge and oxidation state. Yet, the determination of the degree of charge transfer at the interface remains elusive. Here, by combining density functional theory and first-principles molecular dynamics on Pt single atoms deposited on the CeO2 (100) surface, we show that the common representation of a static metal charge is oversimplified. Instead, we identify several well-defined charge states that are dynamically interconnected and thus coexist. The origin of this new class of strong metal–support interactions is the relative position of the Ce(4f) levels with respect to those of the noble metal, allowing electron injection to (or recovery from) the support. This process is phonon-assisted, as the Ce(4f) levels adjust by surface atom displacement, and appears for other metals (Ni) and supports (TiO2). Our dynamic model explains the unique reactivity found for activated single Pt atoms on ceria able to perform CO oxidation, meeting the Department of Energy 150 °C challenge for emissions.
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This research has been supported by the Ministerio de Economía y Competitividad (CTQ2015-68770-R). The authors acknowledge BSC-RES and BIFI for providing generous computational resources. We also thank A. Bruix for critically reading the manuscript, and T. Schäfer for help with the random phase approximation (RPA) methodology.
The authors declare no competing interests.
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Supplementary Notes 1–6, Figs. 1–14, Tables 1–9, video captions 1–4 and references 1–5
Molecular dynamics simulation of polaron-induced electron transfer between a single Pt atom and its support—a (2 × 2) CeO2 supercell with a 2O termination.
Molecular dynamics simulation of polaron-induced electron transfer between a single Pt atom and its support—a (2 × 2) CeO2 supercell with a 3O termination.
Molecular dynamics simulation of polaron-induced electron transfer between a single Pt atom and its support—a (2 × 2) CeO2 supercell with a 4O termination.
Molecular dynamics simulation of polaron-induced electron transfer between a single Pt atom and its support—a (3 × 3) CeO2 supercell with a 2O termination.
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Daelman, N., Capdevila-Cortada, M. & López, N. Dynamic charge and oxidation state of Pt/CeO2 single-atom catalysts. Nat. Mater. 18, 1215–1221 (2019). https://doi.org/10.1038/s41563-019-0444-y
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