Imaging the kinetics of anisotropic dissolution of bimetallic core\u2013shell nanocubes using graphene liquid cells

Lei Chen,Jun Chen,Xingchen Ye,Michael Engel,Alberto Leonardi,Dong Su,Na Li,Muhan Cao,Qiao Zhang

doi:10.1038/s41467-020-16645-3

Abstract

Chemical design of multicomponent nanocrystals requires atomic-level understanding of reaction kinetics. Here, we apply single-particle imaging coupled with atomistic simulation to study reaction pathways and rates of Pd@Au and Cu@Au core-shell nanocubes undergoing oxidative dissolution. Quantitative analysis of etching kinetics using in situ transmission electron microscopy (TEM) imaging reveals that the dissolution mechanism changes from predominantly edge-selective to layer-by-layer removal of Au atoms as the reaction progresses. Dissolution of the Au shell slows down when both metals are exposed, which we attribute to galvanic corrosion protection. Morphological transformations are determined by intrinsic anisotropy due to coordination-number-dependent atom removal rates and extrinsic anisotropy induced by the graphene window. Our work demonstrates that bimetallic core-shell nanocrystals are excellent probes for the local physicochemical conditions inside TEM liquid cells. Furthermore, single-particle TEM imaging and atomistic simulation of reaction trajectories can inform future design strategies for compositionally and architecturally sophisticated nanocrystals.

Highlights

Chemical design of multicomponent nanocrystals requires atomic-level understanding of reaction kinetics
We report graphene liquid cell (GLC) transmission electron microscopy (TEM) imaging of oxidative dissolution of core–shell nanocubes composed of dissimilar metals
We investigated the reaction kinetics during dissolution of well-defined bimetallic core–shell nanocubes using real-time GLC TEM imaging and atomistic Monte Carlo (MC) simulations

Summary

Introduction

Chemical design of multicomponent nanocrystals requires atomic-level understanding of reaction kinetics. We apply single-particle imaging coupled with atomistic simulation to study reaction pathways and rates of Pd@Au and Cu@Au core-shell nanocubes undergoing oxidative dissolution. Quantitative analysis of etching kinetics using in situ transmission electron microscopy (TEM) imaging reveals that the dissolution mechanism changes from predominantly edge-selective to layer-by-layer removal of Au atoms as the reaction progresses. Several studies imaged dissolution events on individual monometallic nanocrystals with in situ liquid cell TEM techniques[18,19,21]. We report graphene liquid cell (GLC) TEM imaging of oxidative dissolution of core–shell nanocubes composed of dissimilar metals. A detailed mechanistic understanding of how the distinct reactivity between core and shell metals influences shape transformation pathways and dissolution kinetics is at present not available due to the lack of systematic single-particle experimental studies

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Conclusion