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An atomic-scale view of single-site Pt catalysis for low-temperature CO oxidation

Abstract

Single-atom catalysts have attracted great attention in recent years due to their high efficiencies and cost savings. However, there is debate concerning the nature of the active site, interaction with the support, and mechanism by which single-atom catalysts operate. Here, using a combined surface science and theory approach, we designed a model system in which we unambiguously show that individual Pt atoms on a well-defined Cu2O film are able to perform CO oxidation at low temperatures. Isotopic labelling studies reveal that oxygen is supplied by the support. Density functional theory rationalizes the reaction mechanism and confirms X-ray photoelectron spectroscopy measurements of the neutral charge state of Pt. Scanning tunnelling microscopy enables visualization of the active site as the reaction progresses, and infrared measurements of the CO stretch frequency are consistent with atomically dispersed Pt atoms. These results serve as a benchmark for characterizing, understanding and designing other single-atom catalysts.

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Fig. 1: Characterization of CO stretch frequencies at Pt single atoms and nanoparticles.
Fig. 2: TPD studies of CO oxidation by Pt supported on the ‘29’ copper oxide.
Fig. 3: Visualization of the CO oxidation mechanism by STM and rationalization by DFT.
Fig. 4: Electronic structure characterization of oxide-supported Pt atoms.

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Acknowledgements

The surface science work at Tufts was supported by the Department of Energy Basic Energy Sciences programme under grant number DE-FG02-05ER15730. M.D.M. thanks Tufts Chemistry for an Illumina Fellowship. Financial support at Washington State University was provided by the National Science Foundation Early-concept Grants for Exploratory Research programme under contract number CBET-1552320 and the CAREER programme under contract number CBET-1653561. Our thanks also go to the donors of the American Chemical Society Petroleum Research Fund. A portion of the computer time for the computational work was performed at the Environmental Molecular Sciences Laboratory—a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research and located at the Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is a multi-programme national laboratory operated for the US Department of Energy by Battelle.

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A.J.T. carried out the sample preparation as well as the STM, STS, TPD, XPS and RAIRS experiments, and assisted with writing the manuscript. A.J.R.H. carried out the DFT calculations and assisted with writing the manuscript. M.D.M. assisted with the TPD and STM experiments. R.Z. assisted with the DFT calculations. F.R.L. assisted with the STM imaging and STS experiments. B.C. and A.C.S. assisted with the STM imaging and XPS experiments. J.-S.M. oversaw and guided the DFT calculations and assisted with writing the manuscript. E.C.H.S. conceived the project, directed the study and assisted with writing the manuscript.

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Correspondence to Jean-Sabin McEwen or E. Charles H. Sykes.

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Supplementary Discussion, Supplementary Figures 1–7, Supplementary Table 1 and Supplementary References

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Therrien, A.J., Hensley, A.J.R., Marcinkowski, M.D. et al. An atomic-scale view of single-site Pt catalysis for low-temperature CO oxidation. Nat Catal 1, 192–198 (2018). https://doi.org/10.1038/s41929-018-0028-2

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