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Communication Dans Un Congrès Année : 2018

2D and Fast 3D in situ study of the calcination and reduction of Pd nanocatalysts supported on Alumina in Environmental Transmission Electron Microscopy (ETEM)

Résumé

2D AND FAST 3D IN SITU CALCINATION AND REDUCTION OF Pd NANOCATALYSTS SUPPORTED ON ALUMINA IN ENVIRONMENTAL TRANSMISSION ELECTRON MICROSCOPY Thierry Epicier1, Siddardha Koneti1, Lucian Roiban1, Anne-Sophie Gay2, Priscilla Avenier2 1Université de Lyon, MATEIS, INSA de Lyon, UCB Lyon 1, UMR 5510 CNRS, 69621 Villeurbanne Cedex, France 2IFP Energies nouvelles, Rond-point de l'échangeur de Solaize, BP 3, 69360 Solaize, France Environmental Transmission Electron Microscopy (ETEM) has recently open the way to operando studies of nanomaterials down to the atomic resolution in temperature and under a gaseous atmosphere that may reproduce more or less its real environmental conditions of use for real applications [1]. This is especially relevant in the field of nanoparticles (NPs) used in heterogeneous catalysis. The present work concerns the dynamic evolution of Pd small NPs (1-3 nm in size) supported on delta-Al2O3 platelets during the catalysis preparation process. This system has important applications, for example in petrochemistry or environmental catalysis. The calcination and reduction steps are followed under O2 and H2 up to 500°C in a FEI TITAN-ETEM microscope operated at 300 kV. Nowadays attention is paid to the “identical location” approach in TEM [2], where the same Region of Interest (ROI) is studied ‘before’ and ‘after’ a solicitation (heat treatment, exposure to gas…) performed outside the microscope. Typical results will show that this strategy is implicit in ETEM: the same ROI is naturally tracked at any stage during its dynamic evolution. One of the main key features insuring the catalytic efficiency of NPs is their resistance to sintering and their ability to remain homogeneously distributed during the calcination and reduction processes. The first point has been quantified through size measurements at different stages of the preparation process. The second point requires evaluating the localization of NPs in 3D using Electron Tomography (ET). Conventional ET, either in the Scanning or Bright Field TEM modes, consists in acquiring 2D projections over a large angular range, a time-consuming process hardly compatible with an in situ approach. We have thus developed a fast ET procedure [3] allowing rapid acquisitions of tilt series for volume reconstruction in only 1 or 2 minutes and a few seconds in the best cases [4]. Therefore, several tomograms of the same area are recorded in situ without critical irradiation damage of the sample shortly exposed to the electron beam. Typical examples will be shown including statistical distribution parameters, such as the inter-NPs distances measured in different states [5]. [1] ‘Controlled Atmosphere Transmission Electron Microscopy’, ed. T.W. Hansen, J.B. Wagner, Springer, New York (2016) 332 p. [2] K.J.J. Mayrhofer et al., Chem. Comm. 10 (2008) 1144-1147. [3] L. Roiban et al., J. of Microscopy, 269 (2018) 117-126. [4] H. Banjak et al., Ultramicroscopy, 189 (2018) 109-123. [5] CLYM (www.clym.fr) is acknowledged for access to the ETEM which was financially supported by the CNRS, the Région Rhône-Alpes, the ‘GrandLyon’ and the French Ministry of Research and Higher Education. This work is supported by the French National Research Agency ANR (3DCLEAN project n°15-CE09-0009-01).
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Dates et versions

hal-01934081 , version 1 (25-11-2018)

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  • HAL Id : hal-01934081 , version 1

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Thierry Epicier, Siddardha Koneti, Lucian Roiban, Anne-Sophie Gay, Amandine Cabiac, et al.. 2D and Fast 3D in situ study of the calcination and reduction of Pd nanocatalysts supported on Alumina in Environmental Transmission Electron Microscopy (ETEM). Matériaux 2018, Nov 2018, Strasbourg, France. ⟨hal-01934081⟩
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