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Title: In situ study of nucleation and growth dynamics of Au nanoparticles on MoS 2 nanoflakes
Two-dimensional (2D) substrates decorated with metal nanoparticles offer new opportunities to achieve high-performance catalytic behavior. However, little is known on how the substrates control the nucleation and growth processes of the nanoparticles. This paper presents the visualization of dynamic nucleation and growth processes of gold nanoparticles on ultrathin MoS 2 nanoflakes by in situ liquid-cell transmission electron microscopy (TEM). The galvanic displacement resulting in Au nuclei formation on MoS 2 was observed in real time inside the liquid cell. We found that the growth mechanism of Au particles on pristine MoS 2 is in between diffusion-limited and reaction-limited, possibly due to the presence of electrochemical Ostwald ripening. A larger size distribution and more orientation variation is observed for the Au particles along the MoS 2 edge than on the interior. Differing from pristine MoS 2 , sulfur vacancies on MoS 2 induce Au particle diffusion and coalescence during the growth process. Density functional theory (DFT) calculations show that the size difference is because the exposed molybdenum atoms at the edge with dangling bonds can strongly interact with Au atoms, whereas sulfur atoms on the MoS 2 interior have no dangling bonds and weakly interact with gold atoms. In addition, S vacancies on MoS 2 generate strong nucleation centers that can promote diffusion and coalescence of Au nanoparticles. The present work provides key insights into the role of 2D materials in controlling the size and orientation of noble metal nanoparticles vital to the design of next generation catalysts.  more » « less
Award ID(s):
1809439 1809085
Author(s) / Creator(s):
; ; ; ; ; ; ;
Date Published:
Journal Name:
Page Range / eLocation ID:
15809 to 15818
Medium: X
Sponsoring Org:
National Science Foundation
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