Imaging the Kinetics of Anisotropic Dissolution of Bimetallic Core–Shell Nanocubes Using Graphene Liquid Cells
Lei Chen,1,2 Alberto Leonardi,3 Jun Chen,2 Muhan Cao,2 Na Li,4,5 Dong Su,4 Qiao Zhang,1,* Michael Engel3,* & Xingchen Ye2,*
1Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, 215123 Suzhou, China.
2Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.
3Institute for Multiscale Simulation, IZNF, Friedrich-Alexander University Erlangen-Nürnberg, 91058 Erlangen, Germany.
4Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA.
5Frontier Institute of Chemistry, Frontier Institute of Science and Technology jointly with College of Science, Xi’an Jiaotong University, 710054 Xi’an, Shanxi, China.
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.