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제  목 : Surface analysis of catalysts by high-sensitivity Low Energy Ion Scattering (LEIS)

연  사 : Diplom. Philipp Bruner(IONTOF GmbH, Münster, Germany)

일  시 : 2021년 3월 4일(목) 오후 4시 30분

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방번호: 170 974 2739

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Surface analysis of catalysts by
high-sensitivity Low Energy Ion Scattering (LEIS)

Philipp Brüner¹, Thomas Grehl^1
 1IONTOF GmbH, Münster, Germany

The outermost atoms of a surface are the analytically relevant part of a catalyst. While other analytical tools (such as XPS) probe an average of many atomic layers, Low Energy Ion Scattering (LEIS) selectively analyses the outer atomic layer. It determines the elemental composition quantitatively, making it a unique tool in the understanding of catalysts.

With high-sensitivity LEIS, catalysts can be analysed under static (= non-destructive) conditions. The sensitivity (< 50 ppm of a monolayer for the heavier elements) is sufficient to easily detect low loadings of the active phase. This permits the analysis of both model and real-world catalysts. From the elemental composition of the outer atomic layer, further sample properties can be deducted: Average particle size, core-shell structure of nanoparticles, distinction of adsorption sites, unexpected contamination etc.

After an introduction of the technique, the focus will be on catalysts for which we gained valuable information that is difficult to obtain with other analytic techniques. This includes a single atom Pt catalyst on a CeO₂ support [1], where it is possible to measure the fraction of single Pt atoms. Even for loading up to 4 wt. %, a significant fraction of the Pt is present as single atoms available for catalysis. This and other examples will illustrate the application of LEIS to relevant catalyst materials.

References

[1] Kunwar et al., ACS Catal. 2019, 9, 3978−3990, DOI: 10.1021/acscatal.8b04885