In Situ TEM Studies of Catalysts Using Windowed Gas Cells

Fan, Yi; Xu, Mingjie; Dai, Sheng; Tieu, Peter; Ren, Xiaobing; Pan, Xiaoqing

doi:10.3390/catal10070779

Cited by 29 publications

(16 citation statements)

References 107 publications

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“…With the advent of high-pressure gas cells and TEM aberration correction, ETEM nowadays enables structural dynamics to be followed in gas conditions up to atmospheric pressure with resolution down to the atomic scale. [23,24] Additionally, ab initio molecular dynamics (AIMD) has been shown to be an efficient method for exploring the conformational three-dimensional complexity of metal NPs in presence of gas adsorbates, [25] providing dynamic trajectories that links different possible structural changes. In this work, the structural dynamics of Au NPs with sizes ranging from 7 nm to 1.5 nm supported on anatase-type titanium oxide (Figure S1, Supporting Information) was examined for the first time, by ETEM at the atomic scale upon exposure to H 2 at atmospheric pressure and at various temperatures.…”

Section: Introductionmentioning

confidence: 99%

Revealing Size Dependent Structural Transitions in Supported Gold Nanoparticles in Hydrogen at Atmospheric Pressure

Nassereddine

Wang

Loffreda

et al. 2021

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activity of Au NPs with size smaller than 5 nm has been often attributed to sizedependent physical features such as the fraction of surface atoms. [5][6][7] For instance, in reactions of hydrogenation, it is widely accepted that surface atoms on small particles are much more active than those on large particles since the fraction of low coordinated sites, that is, at edges and corners, which are the hydrogen activation sites, increases when size decreases. [8][9][10][11] This concept has been largely adopted for studying the reactivity of Au NPs, especially by theoreticians and surface science researchers. [12] The common practice is to consider Au nanoparticles as perfect model crystals with well-defined symmetry and static surface facets interacting with low coverage of gas molecules. However, the effect of adsorbates, which induces surface changes, is generally neglected in these studies. [13][14][15] This is a serious drawback that may prevent reliable description of the catalyst reactivity that mainly depends on the configuration of the surface. Aside from structural effects, quantum size effects are also frequently invoked to explain the exceptional activity of Au NPs. [16,17] For instance, using Density Functional Theory, Illas et al. have reported that the minimum energy pathway of O 2 dissociation for different Au NPs is chemically similar whichThe enhancement of the catalytic activity of gold nanoparticles with their decreasing size is often attributed to the increasing proportion of low-coordinated surface sites. This correlation is based on the paradigmatic picture of working gold nanoparticles as perfect crystal forms having complete and static outer surface layers whatever their size. This picture is incomplete as catalysts can dynamically change their structure according to the reaction conditions and as such changes can be eventually size-dependent. In this work, using aberration-corrected environmental electron microscopy, size-dependent crystal structure and morphological evolution in gold nanoparticles exposed to hydrogen at atmospheric pressure, with loss of the face-centered cubic crystal structure of gold for particle size below 4 nm, are revealed for the first time. Theoretical calculations highlight the role of mobile gold atoms in the observed symmetry changes and particle reshaping in the critical size regime. An unprecedented stable surface molecular structure of hydrogenated gold decorating a highly distorted core is identified. By combining atomic scale in situ observations and modeling of nanoparticle structure under relevant reaction conditions, this work provides a fundamental understanding of the size-dependent reactivity of gold nanoparticles with a precise picture of their surface at working conditions.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202104571.

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Section: Introductionmentioning

confidence: 99%

Revealing Size Dependent Structural Transitions in Supported Gold Nanoparticles in Hydrogen at Atmospheric Pressure

Nassereddine

Wang

Loffreda

et al. 2021

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“…After reaching 950 °C, the switch to O2 atmosphere promote Compared to the ex situ STEM observations for the actual aged catalyst (Figure 1), the in situ observations in vacuum (Figure 2) varied slightly, while those in N 2 or 1% O 2 (balance N 2 ) (Figure 6) exhibited greater similarity. This result shows that the gas cell is effective in the observation of real conditions, and the beam effects should be eliminated in in situ TEM studies for catalytic analysis [20].…”

Section: In Situ Tem Observation In N2 and O2 Atmospheresmentioning

confidence: 89%

In Situ TEM Study of Rh Particle Sintering for Three-Way Catalysts in High Temperatures

Nakayama

Nagata²,

Abe

et al. 2020

Catalysts

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One of the main factors in the deterioration of automobile three-way catalysts is the sintering of platinum group metals (PGMs). In this study, we used in situ tunneling electron microscopy (TEM) to examine the sintering of Rh particles as the temperature increases. Two types of environmental conditions were tested, namely, vacuum atmosphere with heating up to 1050 °C, and N2 with/without 1% O2 at 1 atm and up to 1000 °C. Under vacuum, Rh particles appeared to be immersed in ZrO2. In contrast, at 1 atm N2 with or without 1% O2, the sintered Rh particles appeared spherical and not immersed in ZrO2. The latter trend of Rh sintering resembles the actual engine-aged catalyst observed ex situ in this study. In the N2 atmosphere, the sintering of support material (ZrO2 or Y-ZrO2) was first observed by in situ TEM, followed by Rh particle sintering. The Rh particle size was slightly smaller on Y-ZrO2 compared to that on ZrO2. To better understand these experimental results, density functional theory was used to calculate the systems’ junction energies, assuming three layers of Rh(111) 4 × 4 structures joined to the support material (ZrO2 and Y-ZrO2). The calculated energies were consistent with the in situ TEM observations in the N2 atmosphere.

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“…[1] In the past decade, there has been a surge of interest in developing and employing in situ/operando electron microscopic techniques for atomic-scale and nanoscale visualization of the active sites of catalysts under the heterogeneous reaction conditions that are relevant to clean and sustainable energy reactions. Some of the important aspects of the progress have been highlighted by several outstanding and comprehensive reviews on the development of transmission electron microscopy (TEM) based in situ/operando techniques, [2][3][4][5][6][7][8][9][10][11] including the in situ and operando TEM techniques for studying energy-related reactions, [11] and the structural reconstruction under controlled atmosphere, [12][13][14][15][16][17][18][19][20][21] which provided excellent coverages on in situ TEM methods and scientific merits in terms of the reaction cell design, catalyst synthesis, and selected catalytic reactions. In heterogeneous catalysis, one of the most fundamental focal points is the understanding of the dynamic surface-active sites of a solid catalyst under the specific catalytic reaction condition, which has made significant progress in recent years as a result of the advancement of in situ/operando TEM techniques.…”

Section: Introductionmentioning

confidence: 99%

Insights into Heterogeneous Catalysts under Reaction Conditions by In Situ/Operando Electron Microscopy

Cheng

Wang

Chen

et al. 2022

Advanced Energy Materials

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The advancement of clean energy and environment depends strongly on the development of efficient catalysts in a wide range of heterogeneous catalytic reactions, which has benefited from transmission electron microscopic techniques in determining the atomic‐scale morphologies and structures. However, it is the morphology and structure under the catalytic reaction conditions that determine the performance of the catalyst, which has captured a surge of interest in developing and applying in situ/operando transmission electron microscopic techniques in heterogeneous catalysis. The major theme of this review is to highlight some of the most recent insights into heterogeneous catalysts under the relevant reaction conditions using in situ/operando transmission electron microscopic techniques. Rather than a comprehensive overview of the basic principles of in situ/operando techniques, this review focuses on the insights into the atomic‐scale/nanoscale details of various catalysts ranging from single‐component to multicomponent catalysts under heterogeneous catalytic, electrocatalytic, and photocatalytic reaction conditions involving both gas–solid and liquid–solid interfaces. This focus is coupled with discussions of the correlation of the atomic, molecular, and nanoscale morphology, composition, and structure with the catalytic properties under the reaction conditions, shining light on the challenges and opportunities in design of nanostructured catalysts for clean and sustainable energy applications.

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In Situ TEM Studies of Catalysts Using Windowed Gas Cells

Cited by 29 publications

References 107 publications

Revealing Size Dependent Structural Transitions in Supported Gold Nanoparticles in Hydrogen at Atmospheric Pressure

Revealing Size Dependent Structural Transitions in Supported Gold Nanoparticles in Hydrogen at Atmospheric Pressure

In Situ TEM Study of Rh Particle Sintering for Three-Way Catalysts in High Temperatures

Insights into Heterogeneous Catalysts under Reaction Conditions by In Situ/Operando Electron Microscopy

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