X-ray absorption: Principles, applications, techniques of EXAFS, SEXAFS, and XANES

Jones, Robert G.

doi:10.1016/0160-9327(88)90177-9

Cited by 143 publications

(253 citation statements)

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“…Moreover, the operando XAS can provide the electronic information during the reaction, which further studies the changes occurring on the EMSI during the reaction. [64] Firstly, taking Fe-N-C for example, Guo et al designed a catalyst with ultrasmall cluster and single-atom Fe sites supported by g-C 3 N 4 , called I-FeN x /g-C 3 N 4 for oxidation reactions. As the results from XANES (Figure 7a) show, the white line peak of I-FeN x /g-C 3 N 4 is much higher than that of Fe foil, which indicates that the occupy of 3d orbital in I-FeN x /g-C 3 N 4 is much less and more electron transfers from the Fe atom to the surrounding N atoms.…”

Section: X-ray Absorption Spectroscopymentioning

confidence: 99%

Electronic Metal–Support Interaction of Single‐Atom Catalysts and Applications in Electrocatalysis

et al. 2020

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between the electronic structure and catalytic efficiency of heterogenous catalysts. Dating back to 1930s, the concept of "electronic factor" was proposed by G. M. Schwab to describe the influence of electronic interaction on catalytic behavior of supported catalyst and divided the interaction into two parts, structural and synergetic ones. [4] Electrons transferring between the metal and the support was first under consideration when it came to the catalysis. After that, S. J. Tauster used the term of "strong metal-support interaction" (SMSI) to describe the chemisorption properties of group VIII elements supported by a metal oxide (e.g. SiO 2 , MgO) in 1978. [5] Later the concept was broadened to interaction between any metallic species and support, based on the experimental phenomena. [6] Till that time, based on the early characterization of surface science, researchers had realized that the active site might change during the process from metallic to an SMSI state, which was indicated to be covered or encapsulated by the support. [7] Among many hypotheses concerning the mechanism of SMSI, electron transfer between the metal and the support has been adapted by many researchers, and was confirmed by Rodriguez based on X-ray crystallography and UV photoemission spectroscopy in 1990s. [8] Then almost at the same time that the term of SACs was formally put forward, C. T. Campbell proposed the concept of "electronic metal-support interaction" (EMSI). As Campbell described, the chemical and catalytic properties might be affected by the electronic perturbations (i.e., shifts in the energy of d-band center) due to the EMSI. [9] In other words, the EMSI gave a much more detailed explanation of the enhanced properties of supported catalysts than SMSI, indicating that the study on catalysis was finally pushed to the electronic scale after so many years. [9b,c,10] Unfortunately, for metal particles or clusters, the accurate identification of electronic state is often difficult or even impossible. [11] The most reliable way to overcome the barrier above is to develop the catalyst based on single-atom metal that avoids intrinsic metal effects, including the electronic quantum size effect as well as structure-sensitivity geometrical effect. [12] Therefore, the rise of SACs provides a nearly perfect model to study the EMSI. As the supported metal species downsize to the single atom, the interaction between active site and support is always uniform, which can be much easier to be characterized by both experiment and theoretical calculation. [13] With the help of advanced techniques, for instance, X-ray absorption spectroscopy (XAS), the information about electronic The electronic metal-support interaction (EMSI), which acts as a bridge between theoretical electronic study and the design of heterogenous catalysts, has attracted much attention. Utilizing the interaction between the metal and the support is one of the most essential strategies to enhance electrocatalytic efficiency due to structural and synergetic promotion. To ...

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Section: X-ray Absorption Spectroscopymentioning

confidence: 99%

Electronic Metal–Support Interaction of Single‐Atom Catalysts and Applications in Electrocatalysis

et al. 2020

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“…XAS is a synchrotron-based characterization which consists of X-ray absorption near edge structure (XANES) and extended Xray absorption fine structure (EXAFS). [46] The XAS has acted as a proper choice to obtain the information about the active site on SACs due to its high testing efficiency and atomic scale resolution. [47] Therefore, many works have been focused on the using XAS to identify the active sites on SACs, which is very crucial to construct the relationship between the catalytic efficiency and micro structure.…”

Section: X-ray Absorption Spectroscopy (Xas)mentioning

confidence: 99%

Identifying the Types and Characterization of the Active Sites on M−X−C Single‐Atom Catalysts

Yang

Wang

2020

ChemPhysChem

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Single atom catalysts (SACs) have attracted much attention in recent years. As an essential group in SACs, MÀ XÀ C (X = nonmetallic element) materials have been demonstrated to be efficient in many reactions. However, identifying the active sites on MÀ XÀ C, especially under working conditions, is still challenging, which is crucial for chemists to further understand the mechanism underlying the reaction and better design proper SACs for specific reactions. Herein, the types and characterization of MÀ XÀ C are comprehensively summarized and discussed in this review. In addition to the basic information above, the challenges and opportunities remaining in this field will be also proposed to present a perspective to the research on the next step.

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“…Some excellent textbooks and reviews on X-ray absorption spectroscopy have been published. Therefore, we only present here some essential principles and theoretical elements evolving the XAFS technique [ 12 , 24 , 25 , 26 , 27 , 28 , 29 ].…”

Section: Physical Principle Of Xafsmentioning

confidence: 99%

“…The amplitude and frequency of sinusoidal modulation of μ ( E ) depend respectively on the number and type of neighboring atoms and their distances from the absorber atom. This simple description of the physical phenomenon associated with the EXAFS oscillations was formulated in a general theory that presupposes the existence of simple backscatter processes between the absorber atom and the first neighboring atoms, shorter photoelectron wavelengths, a localized spherical wave and the study of the structure within a short-range distance [ 24 , 25 , 26 , 27 , 28 , 29 ].…”

Section: Physical Principle Of Xafsmentioning

confidence: 99%

“…In the case of energies 50 eV above the absorption edge and the case of systems with the thermal and static disorder, the EXAFS oscillations, χ(k ), can be described as [ 10 , 28 ]:

where f j is the backscattering amplitude of each neighbor N j atom type j . This equation contains terms corresponding to a damping disorders such as Gaussian with a Debye-Waller factor σ 2 , and the term exp (−2 R j /λ(k )) related to inelastic losses in the diffusion process where λ ( k ) is the mean free path of the ejected electron, and S 0 ( k ) is the reduction term due to multi-electron effects.…”

Section: Physical Principle Of Xafsmentioning

confidence: 99%

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X-ray Absorption Fine Structure (XAFS) Studies of Oxide Glasses—A 45-Year Overview

Mastelaro

Zanotto

2018

Materials

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X-ray Absorption Fine Structure (XAFS) spectroscopy has been widely used to characterize the short-range order of glassy materials since the theoretical basis was established 45 years ago. Soon after the technique became accessible, mainly due to the existence of Synchrotron laboratories, a wide range of glassy materials was characterized. Silicate glasses have been the most studied because they are easy to prepare, they have commercial value and are similar to natural glasses, but borate, germanate, phosphate, tellurite and other less frequent oxide glasses have also been studied. In this manuscript, we review reported advances in the structural characterization of oxide-based glasses using this technique. A focus is on structural characterization of transition metal ions, especially Ti, Fe, and Ni, and their role in different properties of synthetic oxide-based glasses, as well as their important function in the formation of natural glasses and magmas, and in nucleation and crystallization. We also give some examples of XAFS applications for structural characterization of glasses submitted to high pressure, glasses used to store radioactive waste and medieval glasses. This updated, comprehensive review will likely serve as a useful guide to clarify the details of the short-range structure of oxide glasses.

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X-ray absorption: Principles, applications, techniques of EXAFS, SEXAFS, and XANES

Cited by 143 publications

References 0 publications

Electronic Metal–Support Interaction of Single‐Atom Catalysts and Applications in Electrocatalysis

Electronic Metal–Support Interaction of Single‐Atom Catalysts and Applications in Electrocatalysis

Identifying the Types and Characterization of the Active Sites on M−X−C Single‐Atom Catalysts

X-ray Absorption Fine Structure (XAFS) Studies of Oxide Glasses—A 45-Year Overview

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