Atomic-Scale Mechanism on Nucleation and Growth of Mo 2 C Nanoparticles Revealed by in Situ Transmission Electron Microscopy

• Published in: Nano letters Vol. 16; no. 12; pp. 7875 - 7881
• Main Authors: Fei, Linfeng, Ng, Sheung Mei, Lu, Wei, Xu, Ming, Shu, Longlong, Zhang, Wei-Bing, Yong, Zehui, Sun, Tieyu, Lam, Chi Hang, Leung, Chi Wah, Mak, Chee Leung, Wang, Yu
• Format: Journal Article
• Language: English
• Published: United States 14-12-2016
• Subjects: nucleation; Transmission electron microscopy; nanoparticles; crystal growth; in situ heating; molybdenum carbide
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.6b04160

With a similar electronic structure as that of platinum, molybdenum carbide (Mo
C) holds significant potential as a high performance catalyst across many chemical reactions. Empirically, the precise control of particle size, shape, and surface nature during synthesis largely determines the catalytic performance of nanoparticles, giving rise to the need of clarifying the underlying growth characteristics in the nucleation and growth of Mo
C. However, the high-temperature annealing involved during the growth of carbides makes it difficult to directly observe and understand the nucleation and growth processes. Here, we report on the use of advanced in situ transmission electron microscopy with atomic resolution to reveal a three-stage mechanism during the growth of Mo
C nanoparticles over a wide temperature range: initial nucleation via a mechanism consistent with spinodal decomposition, subsequent particle coalescence and monomer attachment, and final surface faceting to well-defined particles with minimum surface energy. These microscopic observations made under a heating atmosphere offer new perspectives toward the design of carbide-based catalysts, as well as the tuning of their catalytic performances.