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Counting electrons on supported nanoparticles

Abstract

Electronic interactions between metal nanoparticles and oxide supports control the functionality of nanomaterials, for example, the stability, the activity and the selectivity of catalysts1,2,3,4,5. Such interactions involve electron transfer across the metal/support interface. In this work we quantify this charge transfer on a well-defined platinum/ceria catalyst at particle sizes relevant for heterogeneous catalysis. Combining synchrotron-radiation photoelectron spectroscopy, scanning tunnelling microscopy and density functional calculations we show that the charge transfer per Pt atom is largest for Pt particles of around 50 atoms. Here, approximately one electron is transferred per ten Pt atoms from the nanoparticle to the support. For larger particles, the charge transfer reaches its intrinsic limit set by the support. For smaller particles, charge transfer is partially suppressed by nucleation at defects. These mechanistic and quantitative insights into charge transfer will help to make better use of particle size effects and electronic metal–support interactions in metal/oxide nanomaterials.

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Figure 1: Structural characterization of the Pt/CeO2(111) model catalyst.
Figure 2: ‘Counting’ the electrons transferred owing to the EMSI.
Figure 3: Summary of density functional calculations.

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Acknowledgements

This work was financially supported by the European Community (FP7-NMP.2012.1.1-1 project ChipCAT, Reference No. 310191), by the ‘Deutsche Forschungsgemeinschaft’ (DFG) within the Excellence Cluster ‘Engineering of Advanced Materials’ in the framework of the Excellence Initiative, by Spanish MINECO (grant CTQ2012-34969), by the Generalitat de Catalunya (grants 2014SGR97 and XRQTC), and by the Czech Science Foundation (grant 15-06759S). The authors also acknowledge the CERIC-ERIC Consortium for access to experimental facilities and financial support and the COST Action CM1104 for additional support. Computer resources and assistance were provided by the Red Española de Supercomputación. S.M.K. is grateful to Spanish Ministerio de Educación for a pre-doctoral FPU Grant AP2009-3379. The authors thank A. Kaftan for his contribution to the numerical analysis procedure for XPS.

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Authors

Contributions

S.M.K. performed the density functional calculations. S.M.K., S.F. and K.M.N. analysed the calculated data and were involved in the preparation of the manuscript. K.M.N. supervised the theoretical work. Y.L., T.S. and N.T. performed the RPES experiments. Y.L., T.S., A.N. and J.L. were involved in the analysis of the experimental data and the preparation of the manuscript. J.L. and V.M. supervised the experimental work. A.T., V.S., F.D., V.J. and J.M. performed STM and XPS experiments.

Corresponding authors

Correspondence to Konstantin M. Neyman or Jörg Libuda.

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Lykhach, Y., Kozlov, S., Skála, T. et al. Counting electrons on supported nanoparticles. Nature Mater 15, 284–288 (2016). https://doi.org/10.1038/nmat4500

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