XAS Spectroscopy: Related Techniques and Combination with Other Spectroscopic and Scattering Methods

Lamberti, Carlo; Borfecchia, Elisa; Bokhoven, Jeroen A. van; Fernández, M.

doi:10.1002/9781118844243.ch12

Cited by 9 publications

(6 citation statements)

References 285 publications

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“…These findings have important potentiali mplications in the field of catalysis. [47][48][49][50] Evolution as af unction of temperature in the presence of CO of: part a) the intensity of the IR absorptionband at 1365 cm À1 ,w hich is characteristico ft he acetate ligands;p art b) features A( shift in energy) and B (change in intensity) of the derivative XANES spectra (seearrows in the inset of Figure 6a); part c) average particle size as obtained from analysiso ft he SAXS data showninF igure6b.…”

Section: Discussionmentioning

confidence: 99%

The Pyridyl Functional Groups Guide the Formation of Pd Nanoparticles Inside A Porous Poly(4‐Vinyl‐Pyridine)

et al. 2015

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The reactivity of palladium acetate inside a poly(4‐vinylpyridine‐co‐divinylbenzene) polymer is strongly influenced by the establishment of interaction between the Pd precursor and the pyridyl functional group in the polymer. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and simultaneous X‐ray absorption near edge structure (XANES) and small angle X‐ray scattering (SAXS) techniques have been applied to monitor the reactivity of palladium acetate in the presence of H2 and CO as a function of temperature. H2 reduces palladium acetate to Pd nanoparticles and acetic acid. The pyridyl groups in the polymer play a vital role both in stabilizing the formed acetic acid, thus allowing its detection by means of DRIFTS, and the final Pd nanoparticles, which are extremely small and mono‐dispersed. On the contrary, CO does not reduce palladium acetate. Rather, it forms Pd2+ carbonyl adducts, which favor the detachment of the acetate ligands and their thermal degradation. These adducts are well observable by means of SAXS because they cause an important local change of the electronic density.

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Section: Discussionmentioning

confidence: 99%

The Pyridyl Functional Groups Guide the Formation of Pd Nanoparticles Inside A Porous Poly(4‐Vinyl‐Pyridine)

et al. 2015

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“…This issue, however, can be addressed by scanning the energy of the incident X-rays and employing the anomalous X-ray scattering, as discussed above. 399 Recently, PDF analysis was employed to probe the structure of Co 3 O 4 catalysts for OER, 400 to probe rearrangements of the constituent atoms in Pt–Ni catalysts for ORR, 401 , 402 and distributions of different species in Pt–Ir–Co catalysts for ORR. 403 …”

Section: From Descriptors To Physical Models Of Electrocatalyst Strucmentioning

confidence: 99%

“…While the sensitivity of EXAFS is limited to short-range interactions, PDF analysis of scattering data allows one to probe atomic ordering at much longer length scales. ,,− Normally, the X-ray scattering-based PDF analysis lacks the element-sensitivity of EXAFS. This issue, however, can be addressed by scanning the energy of the incident X-rays and employing the anomalous X-ray scattering, as discussed above . Recently, PDF analysis was employed to probe the structure of Co 3 O 4 catalysts for OER, to probe rearrangements of the constituent atoms in Pt–Ni catalysts for ORR, , and distributions of different species in Pt–Ir–Co catalysts for ORR …”

Section: From Descriptors To Physical Models Of Electrocatalyst Struc...mentioning

confidence: 99%

In Situ/Operando Electrocatalyst Characterization by X-ray Absorption Spectroscopy

2020

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During the last decades, X-ray absorption spectroscopy (XAS) has become an indispensable method for probing the structure and composition of heterogeneous catalysts, revealing the nature of the active sites and establishing links between structural motifs in a catalyst, local electronic structure, and catalytic properties. Here we discuss the fundamental principles of the XAS method and describe the progress in the instrumentation and data analysis approaches undertaken for deciphering X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. Recent usages of XAS in the field of heterogeneous catalysis, with emphasis on examples concerning electrocatalysis, will be presented. The latter is a rapidly developing field with immense industrial applications but also unique challenges in terms of the experimental characterization restrictions and advanced modeling approaches required. This review will highlight the new insight that can be gained with XAS on complex real-world electrocatalysts including their working mechanisms and the dynamic processes taking place in the course of a chemical reaction. More specifically, we will discuss applications of in situ and operando XAS to probe the catalyst’s interactions with the environment (support, electrolyte, ligands, adsorbates, reaction products, and intermediates) and its structural, chemical, and electronic transformations as it adapts to the reaction conditions.

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“…d-PDF was obtained by subtracting the PDF signal of the support (i.e., SiO 2 ) from the PDF data of the entire catalyst (Figures 2A and S22). 37,38 S21 and 2B (data collected at 230 °C). The reciprocal space data of the activated catalysts showed broad, yet clear Bragg peaks for all of the catalysts that can be indexed, independent of the Ni:Ga ratio, as a face-centered cubic (fcc)type structure (Supporting Information Figure S21).…”

Section: Structure Of the Catalysts After In Situ Activationmentioning

confidence: 99%

Structure and Role of a Ga-Promoter in Ni-Based Catalysts for the Selective Hydrogenation of CO₂ to Methanol

Zimmerli,

Rochlitz,

Checchia

et al. 2024

JACS Au

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Supported, bimetallic catalysts have shown great promise for the selective hydrogenation of CO 2 to methanol. In this study, we decipher the catalytically active structure of Ni−Ga-based catalysts. To this end, model Ni−Ga-based catalysts, with varying Ni:Ga ratios, were prepared by a surface organometallic chemistry approach. In situ differential pair distribution function (d-PDF) analysis revealed that catalyst activation in H 2 leads to the formation of nanoparticles based on a Ni−Ga face-centered cubic (fcc) alloy along with a small quantity of GaO x . Structure refinements of the d-PDF data enabled us to determine the amount of both alloyed Ga and GaO x species. In situ X-ray absorption spectroscopy experiments confirmed the presence of alloyed Ga and GaO x and indicated that alloying with Ga affects the electronic structure of metallic Ni (viz., Ni δ− ). Both the Ni:Ga ratio in the alloy and the quantity of GaO x are found to minimize methanation and to determine the methanol formation rate and the resulting methanol selectivity. The highest formation rate and methanol selectivity are found for a Ni−Ga alloy having a Ni:Ga ratio of ∼75:25 along with a small quantity of oxidized Ga species (0.14 mol GaO x mol Ni −1). Furthermore, operando infrared spectroscopy experiments indicate that GaO x species play a role in the stabilization of formate surface intermediates, which are subsequently further hydrogenated to methoxy species and ultimately to methanol. Notably, operando XAS shows that alloying between Ni and Ga is maintained under reaction conditions and is key to attaining a high methanol selectivity (by minimizing CO and CH 4 formation), while oxidized Ga species enhance the methanol formation rate.

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XAS Spectroscopy: Related Techniques and Combination with Other Spectroscopic and Scattering Methods

Cited by 9 publications

References 285 publications

The Pyridyl Functional Groups Guide the Formation of Pd Nanoparticles Inside A Porous Poly(4‐Vinyl‐Pyridine)

The Pyridyl Functional Groups Guide the Formation of Pd Nanoparticles Inside A Porous Poly(4‐Vinyl‐Pyridine)

In Situ/Operando Electrocatalyst Characterization by X-ray Absorption Spectroscopy

Structure and Role of a Ga-Promoter in Ni-Based Catalysts for the Selective Hydrogenation of CO₂ to Methanol

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XAS Spectroscopy: Related Techniques and Combination with Other Spectroscopic and Scattering Methods

Cited by 9 publications

References 285 publications

The Pyridyl Functional Groups Guide the Formation of Pd Nanoparticles Inside A Porous Poly(4‐Vinyl‐Pyridine)

The Pyridyl Functional Groups Guide the Formation of Pd Nanoparticles Inside A Porous Poly(4‐Vinyl‐Pyridine)

In Situ/Operando Electrocatalyst Characterization by X-ray Absorption Spectroscopy

Structure and Role of a Ga-Promoter in Ni-Based Catalysts for the Selective Hydrogenation of CO2 to Methanol

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Structure and Role of a Ga-Promoter in Ni-Based Catalysts for the Selective Hydrogenation of CO₂ to Methanol