Recent Progresses on Structural Reconstruction of Nanosized Metal Catalysts via Controlled-Atmosphere Transmission Electron Microscopy: A Review

Abstract

Metal catalysts are of great importance in the modern chemical industry. It is well-known that the structures of metal catalysts determine their properties. However, recent studies suggested that the structures of metal catalysts change dynamically under reaction conditions, resulting in the deactivation or activation of metal catalysts. This Review summarizes the latest research progresses in the structural reconstruction of metal catalysts via controlled-atmosphere transmission electron microscopy. The stateof-the-art research technologies and crucial factors affecting the nanosized metal catalyst reconstruction are discussed. Various types of reconstruction phenomena are reviewed, including sintering and dispersion, reshaping, composition evolution, surface reconstruction of metal oxides, and strong metal−support interactions. Moreover, recent studies of the structure−property relationship of metal catalysts are also reviewed. Finally, we highlight current challenges and provide the perspectives for future research of this topic. We hope this Review provides insights for the rational design of highperformance metal catalysts.

Confinement Effects in Individual Carbon Encapsulated Nonprecious Metal‐Based Electrocatalysts

“…For example, advanced in situ scanning tunneling microscopy or TEM could provide the information on the structure, composition, and morphology of the catalysts, while in situ photoemission electron microscopy could obtain the information on the spatial distribution of adsorbates and on reaction processes. [203,204] Moreover, electronic/geometric structure, coordination environment, structural reconstruction, and catalyst-reactant/intermediate interaction could be performed by in situ X-ray absorption spectroscopy, during both the synthesis process and ongoing reaction. The in situ Raman and infrared spectroscopy could also provide the information on chemical state and phase transition, and surface adsorbates/reaction intermediates.…”

Synthesis of Carbon Nanotubes by Floating Catalyst Chemical Vapor Deposition and Their Applications

“…This could cover a wide pressure range from ≈10 −5 Pa to atmospheric pressure, allowing for a better understanding under near-reactive conditions. [193] With ETEM, there is clear evidence of several phenomena, such as multiple nucleation processes [194] and correlations between particle size and tube diameter, [195] which are two of the key questions in understanding the FCCVD CNT growth mechanism. Additionally, because of the technical difficulty in directly resolving and tracking a flying catalyst particle and nanotube under a fast and random dynamical process, a model catalyst (or growth promoter) and analogous environments could be designed to mimic the floating catalysts for CNT growth.…”

Tracking the redox reaction-induced reconstruction of NiAu nanoparticles via environmental scanning transmission electron microscopy

“…With the emergence and development of identical location scanning transmission electron microscopy (IL-STEM) and environmental scanning transmission electron microscopy (E-STEM) in the past few decades, the dynamic behaviors of bimetallic catalysts have been directly observed. 13,14 They are more persuasive and time-saving compared with the tra-ditional post-mortem or ex situ methods for the structural characterization of catalysts, which mainly focus on the initial and final states without focusing on a same sample region. 15,16 When further equipped with spherical aberration correctors, details of atmosphere-related structure reconstruction can be imaged at the atomic scale.…”