Twin boundary migration in an individual platinum nanocrystal during catalytic CO oxidation

Jérôme Carnis,Maxime Dupraz,Longfei Wu,Tobias U Schülli,Aseem Rajan Kshirsagar,Nimrod Gazit,Ehud Almog,M Texier ,Lu Gao,S Labat ,Steven Leake ,O Thomas ,Freddy E Oropeza,Andréa Campos ,Emiel J M Hensen,Jan P Hofmann,Jean Sébastien Micha ,Roberta Poloni,Luc Favre,Eugen Rabkin,M.-I Richard

doi:10.1038/s41467-021-25625-0

Abstract

At the nanoscale, elastic strain and crystal defects largely influence the properties and functionalities of materials. The ability to predict the structural evolution of catalytic nanocrystals during the reaction is of primary importance for catalyst design. However, to date, imaging and characterising the structure of defects inside a nanocrystal in three-dimensions and in situ during reaction has remained a challenge. We report here an unusual twin boundary migration process in a single platinum nanoparticle during CO oxidation using Bragg coherent diffraction imaging as the characterisation tool. Density functional theory calculations show that twin migration can be correlated with the relative change in the interfacial energies of the free surfaces exposed to CO. The x-ray technique also reveals particle reshaping during the reaction. In situ and non-invasive structural characterisation of defects during reaction opens new avenues for understanding defect behaviour in confined crystals and paves the way for strain and defect engineering.

Highlights

At the nanoscale, elastic strain and crystal defects largely influence the properties and functionalities of materials
We demonstrate the capabilities of Bragg coherent diffraction imaging (BCDI) to reveal in 3D the local morphology, strain and defect evolution in a single Pt nanoparticle in situ during catalytic CO oxidation reaction at elevated temperatures (450 °C and 500 °C) under Ar, CO, and/or O2 atmosphere at near atmospheric pressure flow conditions
The BCDI measurements were performed by recording the intensity distribution in the vicinity of the specular 111 Pt Bragg reflection, which yields, for example, the 3D diffraction pattern displayed in Fig. 1b, the duration of the measurement being around 4 min 30 s The phase retrieval procedure used for spatial reconstruction of the a Out

Summary

Introduction

Elastic strain and crystal defects largely influence the properties and functionalities of materials. Its amplitude is related to the real space density or to Bragg electron density of the contributing crystal, whereas the phase is equivalent to the displacement field component projected on the Bragg diffraction vector. These two parameters can be resolved with a spatial resolution better than 10 nm[30,31,32]. We demonstrate the capabilities of BCDI to reveal in 3D the local morphology (faceting), strain and defect evolution in a single Pt nanoparticle in situ during catalytic CO oxidation reaction at elevated temperatures (450 °C and 500 °C) under Ar, CO, and/or O2 atmosphere at near atmospheric pressure flow conditions

Methods

Results

Conclusion