Structure of the catalytically active copper–ceria interfacial perimeter

Abstract

Cu/CeO2 catalysts are highly active for the low-temperature water–gas shift—a core reaction in syngas chemistry for tuning the H2/CO/CO2 proportions in feed streams—but the direct identification and quantitative description of the active sites remain challenging. Here we report that the active copper clusters consist of a bottom layer of mainly Cu+ atoms bonded on the oxygen vacancies (Ov) of ceria, in a form of Cu+–Ov–Ce3+, and a top layer of Cu0 atoms coordinated with the underlying Cu+ atoms. This atomic structure model is based on directly observing copper clusters dispersed on ceria by a combination of scanning transmission electron microscopy and electron energy loss spectroscopy, in situ probing of the interfacial copper–ceria bonding environment by infrared spectroscopy and rationalization by density functional theory calculations. These results, together with reaction kinetics, reveal that the reaction occurs at the copper–ceria interfacial perimeter via a site cooperation mechanism: the Cu+ site chemically adsorbs CO whereas the neighbouring Ov–Ce3+ site dissociatively activates H2O.

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Fig. 1: Identification of copper clusters on ceria in the Cu-473 catalyst.
Fig. 2: Geometric structures of copper clusters on ceria in the Cu-773 catalyst.
Fig. 3: Binding environment of the copper–ceria interface probed by in situ infrared spectroscopy.
Fig. 4: Atomic structure of the copper–ceria interfacial perimeter.
Fig. 5: WGS reaction over the Cu-T catalysts.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

This work is supported by the National Natural Science Foundation of China (grant numbers 91645107, 21533009, 21621063 and 21761132031), the Deutsche Forschungsgemeinschaft (WA 2535/2-1), the ‘Science and Technology of Nanosystems’ Programme (grant no. 432202) of Germany and the EU-H2020 research and innovation programme (grant no. 654360 NFFA-Europe). X.Y. and C.Y. thank PhD fellowships sponsored by the China Scholarship Council.

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A.C., J.N., C.J. and Y.L. prepared the catalysts and conducted the reaction tests. X.Y., C.Y., A.N., C.W. and Y.W. performed the UHV infrared analysis. S.K. and J.S. performed chemical titrations and reaction tests. Y.Z., S.M., J.L., T.A. and S.H. conducted the STEM and EELS analyses. M.F.C. and S.F. performed the DFT calculations on the interfacial structure. S.F. and C.W. contributed to thorough discussions on this work. Y.Z., J.S., Y.W. and W.S. designed the experiments, analysed the data and wrote the paper.

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Correspondence to Yan Zhou or Jens Sehested or Yuemin Wang or Wenjie Shen.

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Supplementary Methods, Supplementary Discussion, Supplementary Figures 1–13, Supplementary Tables 1–6, Supplementary References

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Chen, A., Yu, X., Zhou, Y. et al. Structure of the catalytically active copper–ceria interfacial perimeter. Nat Catal 2, 334–341 (2019). https://doi.org/10.1038/s41929-019-0226-6

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