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Issue 31, 2018
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Identifying site-dependent reactivity in oxidation reactions on single Pt particles

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Abstract

Catalytic nanoparticles are heterogeneous in their nature and even within the simplest particle various surface sites exist and influence the catalytic reactivity. Thus, detailed chemical information at the nanoscale is essential for understanding how surface properties and reaction conditions direct the reactivity of different surface sites of catalytic nanoparticles. In this work, hydroxyl-functionalized N-heterocyclic carbene molecules (NHCs) were anchored to the surface of Pt particles and utilized as chemical markers to detect reactivity variations between different surface sites under liquid and gas phase oxidizing conditions. Differences in the chemical reactivity of surface-anchored NHCs were identified using synchrotron-radiation-based infrared nanospectroscopy with a spatial resolution of 20 nanometers. By conducting IR nanospectroscopy measurements, along with complementary spatially averaged IR and X-ray spectroscopy measurements, we identified that enhanced reactivity occurred on the particles' periphery under both gas and liquid phase oxidizing conditions. Under gas phase reaction conditions the NHCs' hydroxyl functional groups underwent preferential oxidization to the acid along the perimeter of the particle. Exposure of the sample to harsher, liquid phase oxidizing conditions induced modification of the NHCs, which was mostly identified at the particle's periphery. Analysis of X-ray absorption spectroscopy measurements revealed that exposure of the sample to oxidizing conditions induced aromatization of the NHCs, presumably due to oxidative dehydrogenation reaction, along with reorientation of the NHCs from perpendicular to parallel to the Pt surface. These results, based on single particle measurements, demonstrate the high reactivity of surface sites that are located at the nanoparticle's periphery and the influence of reaction conditions on site-dependent reactivity.

Graphical abstract: Identifying site-dependent reactivity in oxidation reactions on single Pt particles

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Publication details

The article was received on 30 Apr 2018, accepted on 03 Jul 2018 and first published on 03 Jul 2018


Article type: Edge Article
DOI: 10.1039/C8SC01956H
Citation: Chem. Sci., 2018,9, 6523-6531
  • Open access: Creative Commons BY-NC license
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    Identifying site-dependent reactivity in oxidation reactions on single Pt particles

    S. Dery, S. Kim, D. Haddad, A. Cossaro, A. Verdini, L. Floreano, F. D. Toste and E. Gross, Chem. Sci., 2018, 9, 6523
    DOI: 10.1039/C8SC01956H

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