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In situ structural evolution of model catalysts imaged by Bragg coherent X-ray diffraction

​Mardi 17 novembre 2020 
Publié le 17 novembre 2020

​By Marie-Ingrid Richard

Characterising the structural properties (strain gradients, chemical composition, crystal orientation and defects) inside nanostructures is a grand challenge in materials science. Bragg coherent diffraction imaging (Bragg CDI) can be utilised to address this challenge for crystalline nanostructures. A resolution of the structural properties of less than 10 nm is achieved up-to-date [1, 2]. The capabilities of the Bragg CDI technique will be demonstrated on single nanoparticles for enhanced catalysis.
As an example, the Bragg CDI technique [3, 4] allows understanding the interplay between shape, size, strain, faceting [5], composition and defects at the nanoscale. We will demonstrate that Bragg CDI on a single particle model catalyst makes it possible to map its local strain/defect field and directly image strain build-up close to the facets. We will also show results obtained during in situ [6, 7] and operando Bragg CDI measurements: it was possible to track a single particle in gas or liquid phase environments to monitor its facet changes and to measure its strain/defect response to reaction.
This technique opens pathways to determine and control the internal structure of nanoparticles to tune and optimise them during catalytic and other chemical reactions. This technique should benefit from a unique opportunity: the ESRF EBS Upgrade. This should revolutionise imaging by making it possible to map evolving physico-chemical processes in a slow-motion movie.


​Références 

[1] S. Labat, M.-I. Richard, M. Dupraz, M. Gailhanou, G. Beutier, M. Verdier, F. Mastropietro, T. W. Cornelius, T. U. Schülli, J. Eymery, and O. Thomas, Inversion Domain Boundaries in GaN Wires Revealed by Coherent Bragg Imaging, ACS Nano 9, 9210 (2015).
[2] N. Li, S. Labat, S. J. Leake, M. Dupraz, J. Carnis, T. W. Cornelius, G. Beutier, M. Verdier, V. Favre-Nicolin, T. U. Schülli, O. Thomas, J. Eymery, and M.-I. Richard, Mapping Inversion Domain Boundaries along Single GaN Wires with Bragg Coherent X-Ray Imaging, ACS Nano 14, 10305 (2020).
[3] J. Carnis, L. Gao, S. Labat, Y. Y. Kim, J. P. Hofmann, S. J. Leake, T. U. Schülli, E. J. M. Hensen, O. Thomas, and M.-I. Richard, Towards a Quantitative Determination of Strain in Bragg Coherent X-Ray Diffraction Imaging: Artefacts and Sign Convention in Reconstructions, Sci Rep 9, 1 (2019).
[4] N. Li, M. Dupraz, L. Wu, S. J. Leake, A. Resta, J. Carnis, S. Labat, E. Almog, E. Rabkin, V. Favre-Nicolin, F.-E. Picca, F. Berenguer, R. van de Poll, J. P. Hofmann, A. Vlad, O. Thomas, Y. Garreau, A. Coati, and M.-I. Richard, Continuous Scanning for Bragg Coherent X-Ray Imaging, Sci Rep 10, 12760 (2020).
[5] M.-I. Richard, S. Fernández, J. Eymery, J. P. Hofmann, L. Gao, J. Carnis, S. Labat, V. Favre-Nicolin, E. J. M. Hensen, O. Thomas, T. U. Schülli, and S. J. Leake, Crystallographic Orientation of Facets and Planar Defects in Functional Nanostructures Elucidated by Nano-Focused Coherent Diffractive X-Ray Imaging, Nanoscale 10, 4833 (2018).
[6] M.-I. Richard, S. Fernández, J. P. Hofmann, L. Gao, G. A. Chahine, S. J. Leake, H. Djazouli, Y. De Bortoli, L. Petit, P. Boesecke, S. Labat, E. J. M. Hensen, O. Thomas, and T. Schülli, Reactor for Nano-Focused x-Ray Diffraction and Imaging under Catalytic in Situ Conditions, Review of Scientific Instruments 88, 093902 (2017).
[7] S. Fernández, L. Gao, J. P. Hofmann, J. Carnis, S. Labat, G. A. Chahine, A. J. F. van Hoof, M. W. G. M. (Tiny) Verhoeven, T. U. Schülli, E. J. M. Hensen, O. Thomas, and M.-I. Richard, In Situ Structural Evolution of Single Particle Model Catalysts under Ambient Pressure Reaction Conditions, Nanoscale 11, 331 (2019).