Atomic-scale electron microscopy at ambient pressure

Creemer, J.F.; Helveg, Stig; Hoveling, G.H.; Ullmann, S.; Molenbroek, A.M.; Sarro, P.M.; Zandbergen, H.W.

doi:10.1016/j.ultramic.2008.04.014

Cited by 314 publications

(309 citation statements)

References 26 publications

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“…As this is the same size as many iron oxide crystallites which make up the catalyst, 52 STXM alone has insufficient spatial resolution to probe compositional variations within individual catalyst nanoparticles. However, the 35 nanoreactor used in this study was originally designed for the electron microscope, 56 and future in situ EELS studies may be able to provide complimentary information on a finer length scale. 40 Many systems are hydrated in their native state, and these have also benefited from the introduction of nanoreactors which allow controlled humidity, keeping samples hydrated throughout the experiment.…”

Section: Gas Cells and Fischer-tropsch Catalystsmentioning

confidence: 99%

Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution

et al. 2015

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Two powerful and complementary techniques for chemical characterisation of nanoscale systems are electron energy-loss spectroscopy in the scanning transmission electron microscope, and X-ray absorption spectroscopy in the scanning transmission X-ray microscope. A correlative approach to spectromicroscopy may not only bridge the gaps in spatial and spectral resolution which exist between the two instruments, but also offer unique opportunities for nanoscale characterisation. This review will discuss 10 the similarities of the two spectroscopy techniques and the state of the art for each microscope. Case studies have been selected to illustrate the benefits and limitations of correlative electron and X-ray microscopy techniques. In situ techniques and radiation damage are also discussed. IntroductionGrowth in the development and applications of nanotechnology 15 brings with it an increasing need for characterisation methods capable of providing both structural and chemical analysis on the nanometre scale. Most laboratory based characterisation techniques such as ultra-violet and infra-red spectroscopies, mass spectrometry and thermogravimetric analysis provide spatially 20 averaged information from comparatively large volumes of sample. While these techniques provide a representative overview of the sample, their averaged signals often probe not only the nanomaterial of interest, but also any support material, debris and impurities in heterogeneous structures. In addition, averaged 25 properties miss statistical outliers, which may be critical for the function of the nanomaterial. For characterisation of interfaces or individual nanostructures, techniques with much higher spatial resolutions are essential.There are few available techniques capable of providing 30 chemical information on the nanometre scale. This review will discuss two such methods: electron energy-loss spectroscopy in the scanning transmission electron microscope (STEM-EELS) and X-ray absorption spectroscopy in the scanning transmission X-ray microscope (STXM-XAS). These spectroscopies study the 35 primary processes of inelastic electron scattering or X-ray absorption to obtain chemical information, from chemical speciation analysis to local bonding environments and electronic structure. While the secondary process of X-ray emission also provides chemical information in the electron and X-ray 40 microscopes (by energy dispersive X-ray spectroscopy and X-ray probe X-ray micro-and nano-analysis respectively), these techniques, whilst being very sensitive to low concentrations, are limited to elemental analysis, and they will not be discussed in this review. Although the probe-specimen interactions of EELS 45 and XAS differ (electron scattering and photon absorption, respectively), they provide remarkably similar chemical information. Due to recent advances in diffractive optics for soft (100 eV to 2 keV 1 ) X-rays, as well as monochromators and aberration correctors for electron microscopes, the spatial and 50 spectral resolutions of STXM-XAS...

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Section: Gas Cells and Fischer-tropsch Catalystsmentioning

confidence: 99%

Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution

et al. 2015

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“…This has led to an explosion of interest in in situ TEM, where materials are studied under more realistic environmental conditions 21, 22, 23. Dedicated environmental transmission electron microscope (ETEM) systems allow for atomic resolution imaging at moderate temperature but are limited to pressures of less than ≈50 mbar 24, 25, 26.…”

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confidence: 99%

“…The concomitant multiple scattering which ensues can prevent even light elements from being resolved. As a consequence, most in situ (S)TEM experiments of supported catalysts to date have not used the spectroscopy capabilities of the instrument but have focused on monometallic or model catalyst systems 23, 24, 25. In particular, those with a high atomic number difference between the support and the nanoparticle so that imaging alone can distinguish morphological changes.…”

mentioning

confidence: 99%

In Situ Industrial Bimetallic Catalyst Characterization using Scanning Transmission Electron Microscopy and X‐ray Absorption Spectroscopy at One Atmosphere and Elevated Temperature

Prestat

Kulzick²,

Dietrich³

et al. 2017

ChemPhysChem

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We have developed a new experimental platform for in situ scanning transmission electron microscope (STEM) energy dispersive X‐ray spectroscopy (EDS) which allows real time, nanoscale, elemental and structural changes to be studied at elevated temperature (up to 1000 °C) and pressure (up to 1 atm). Here we demonstrate the first application of this approach to understand complex structural changes occurring during reduction of a bimetallic catalyst, PdCu supported on TiO2, synthesized by wet impregnation. We reveal a heterogeneous evolution of nanoparticle size, distribution, and composition with large differences in reduction behavior for the two metals. We show that the data obtained is complementary to in situ STEM electron energy loss spectroscopy (EELS) and when combined with in situ X‐ray absorption spectroscopy (XAS) allows correlation of bulk chemical state with nanoscale changes in elemental distribution during reduction, facilitating new understanding of the catalytic behavior for this important class of materials.

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“…However, surfaces of most materials tend to restructure in reactive gas environments and such changes have a profound feedback on catalysts' properties. It has therefore remained an important milestone in catalysis and surface sciences to functionalize electron microscopy for operando studies in which the catalyst surface structure and properties are simultaneously evaluated at the atomic-scale and under relevant reaction conditions.Here, we report on a nanoreactor system that enables combined electron microscopy and functional measurements of catalysts [2][3][4][5][6] and is available from Thermo Fisher Scientific. The nanoreactor is a micro-electro-mechanical system device integrating a 5-µm-high, one-pass and bypass-free gas-flow channel, a microheater and an array of 15-nm-thick electron-transparent windows of silicon nitride (Figure 1) [4].…”

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confidence: 99%

Atomic-Resolution Imaging of Heterogeneous Catalysts at Work

Helveg¹,

Elkjcer²,

Jespersen³

et al. 2018

Microsc Microanal

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Transmission electron microscopy (TEM) has become indispensable in the study of heterogeneous catalysts. The ability to acquire atomic-resolution images of catalysts opens up for unprecedented new information about the catalyst surface that benefits the understanding of structure-sensitivity in catalysis [1]. However, surfaces of most materials tend to restructure in reactive gas environments and such changes have a profound feedback on catalysts' properties. It has therefore remained an important milestone in catalysis and surface sciences to functionalize electron microscopy for operando studies in which the catalyst surface structure and properties are simultaneously evaluated at the atomic-scale and under relevant reaction conditions.Here, we report on a nanoreactor system that enables combined electron microscopy and functional measurements of catalysts [2][3][4][5][6] and is available from Thermo Fisher Scientific. The nanoreactor is a micro-electro-mechanical system device integrating a 5-µm-high, one-pass and bypass-free gas-flow channel, a microheater and an array of 15-nm-thick electron-transparent windows of silicon nitride (Figure 1) [4]. This nanoreactor is operational with variable gas flows (0-0.1 sccm/min), ambient pressure levels (> 1 bar) and elevated temperatures (25-700 o C), while maintaining the inherent 1Å resolution in modern electron microscopes. Moreover, mass spectrometry of gas exiting the reaction zone is made possible by the small reaction volume of ca. 0.3 nL and reaction calorimetry is accessed from the power compensation used for isothermal operation of the microheater [6].The nanoreactor performance and application will be showcased by observations of Pt nanoparticles under oxidizing and reducing reaction conditions. Specifically, high-resolution TEM images were acquired of the Pt nanoparticles under exposure to reactive gas environments synchronously with mass spectrometry and calorimetry data. Based on such observations, structure-activity relationship will be outlined for e.g. the steady-state and oscillatory catalytic oxidation of carbon monoxide over Pt nanoparticles [6]. These examples demonstrate exciting possibilities for including information about the exposed surface sites into the description of dynamic properties and functions of catalysts.

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Atomic-scale electron microscopy at ambient pressure

Cited by 314 publications

References 26 publications

Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution

Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution

In Situ Industrial Bimetallic Catalyst Characterization using Scanning Transmission Electron Microscopy and X‐ray Absorption Spectroscopy at One Atmosphere and Elevated Temperature

Atomic-Resolution Imaging of Heterogeneous Catalysts at Work

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