Operation of a bending magnet beamline in large energy bandwidth mode for non-resonant X-ray emission spectroscopy

Dikaya, Olga; Nachtegaal, Maarten; Szlachetko, Jakub; Ebner, Kathrin; Saveleva, Viktoriia A.; Weder, Nicola; Probst, Benjamin; Alberto, Roger; Serebrennikov, D. A.; Clementyev, E. S.; Maksimova, Ksenia; Goikhman, Alexander; Smolentsev, Grigory

doi:10.1016/j.rinp.2020.103212

Cited by 4 publications

(3 citation statements)

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“…minutes by combining energy-dispersive setups [34] and a high incident X-ray flux. [35] Thus, herein we demonstrate the capability of XES to quantify the average, ex situ spin state of a series of Fe-based M/N/C catalysts (Fe/N/Cs). Furthermore, we show for the first time that XES can track potentialinduced effects on this variable under experimental conditions relevant to the oxygen reduction reaction.…”

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confidence: 90%

“…This need for techniques that can discriminate oxidation‐ from spin state could potentially be fulfilled by non‐resonant X‐ray emission spectroscopy (XES), [31–33] which additionally allows in situ experiments requiring acquisition over a few minutes by combining energy‐dispersive setups [34] and a high incident X‐ray flux [35] . Thus, herein we demonstrate the capability of XES to quantify the average, ex situ spin state of a series of Fe‐based M/N/C catalysts (Fe/N/Cs).…”

Section: Figurementioning

confidence: 99%

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Potential‐Induced Spin Changes in Fe/N/C Electrocatalysts Assessed by In Situ X‐ray Emission Spectroscopy

Saveleva

Ebner

et al. 2021

Angewandte Chemie

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confidence: 90%

Section: Figurementioning

confidence: 99%

Potential‐Induced Spin Changes in Fe/N/C Electrocatalysts Assessed by In Situ X‐ray Emission Spectroscopy

Saveleva

Ebner

et al. 2021

Angewandte Chemie

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“…Non-resonant XES does not require a monochromatic incident beam, which considerably relaxes the constraints on the X-ray source. At a synchrotron radiation source or freeelectron laser one can use a 'pink' beam with an energy bandwidth much larger than the core-hole lifetime broadening (Dikaya et al, 2020). High-quality Bragg optics have become available at a reasonable cost which has led to the development of instruments by many research groups.…”

Section: Introductionmentioning

confidence: 99%

The five-analyzer point-to-point scanning crystal spectrometer at ESRF ID26

Glatzel¹,

Harris²,

Marion³

et al. 2021

J Synchrotron Rad

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X-ray emission spectroscopy in a point-to-point focusing geometry using instruments that employ more than one analyzer crystal poses challenges with respect to mechanical design and performance. This work discusses various options for positioning the components and provides the formulas for calculating their relative placement. Ray-tracing calculations were used to determine the geometrical contributions to the energy broadening including the source volume as given by the beam footprint on the sample. The alignment of the instrument is described and examples are given for the performance.

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Potential‐Induced Spin Changes in Fe/N/C Electrocatalysts Assessed by In Situ X‐ray Emission Spectroscopy

Saveleva

Ebner

et al. 2021

Angew Chem Int Ed

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The commercial success of the electrochemical energy conversion technologies required for the decarbonization of the energy sector requires the replacement of the noble metal-based electrocatalysts currently used in (co-)electrolyzers and fuel cells with inexpensive, platinum-group metal-free analogs. Among these, Fe/N/C-type catalysts display promising performances for the reduction of O 2 or CO 2 , but their insufficient activity and stability jeopardize their implementation in such devices. To circumvent these issues, a better understanding of the local geometric and electronic structure of their catalytic active sites under reaction conditions is needed. Herein we shed light on the electronic structure of the molecular sites in two Fe/N/C catalysts by probing their average spin state with X-ray emission spectroscopy (XES). Chiefly, our in situ XES measurements reveal for the first time the existence of reversible, potential-induced spin state changes in these materials.Platinum-group metal (PGM-) free catalysts of the M/N/Ctype (whereby M corresponds to a 3d transition metal) hold great potential as inexpensive replacements for conventional, noble-metal-based materials. Originally developed as electrocatalysts for the oxygen reduction reaction (ORR, relevant to fuel cells [1,2] and metal-air batteries [3][4][5] ), these materials have recently been successfully employed in other catalytic processes, like CO 2 -electroreduction [6,7] or the oxidation of benzene to phenol. [8,9] Nevertheless, their commercial implementation requires further improvements in their activity and stability [1,10] that call for a better understanding of the reactions mechanism and their relation to the operando oxidation-, spin-state and orbital configuration of the Ncoordinated metal sites (M-N x ) regarded as their active centers. [11][12][13][14] These properties have been generally assessed using Mçssbauer [12,15,16] and X-ray absorption [17][18][19] spectroscopy (MS, XAS), which are highly sensitive techniques but also suffer from certain drawbacks. MS, on the one hand, allows distinguishing the chemical environment of the metal species present in iron-based M/N/C catalysts, which have been shown to be the most ORR-active among this material class; however, their heterogeneous composition results in complex spectra requiring a careful deconvolution. The latter is occasionally complemented by the assignment of spin-and oxidation-states to these deconvolution components, based on similarities between the Mçssbauer parameters of the Fe-N x sites in these Fe/N/C catalysts and those of compounds with resembling but better defined M-N 4 centers (like porphyrins or phthalocyanines). [12] However, the long-range structures and electronic properties of these reference compounds are likely to differ from those of the catalysts active sites, thus making a full conclusive analysis difficult. Furthermore, the combination of the low temporal resolution of MS and the low metal contents of M-N x sites (typically < 2 wt. %) in M/N/C catalysts le...

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Operation of a bending magnet beamline in large energy bandwidth mode for non-resonant X-ray emission spectroscopy

Cited by 4 publications

References 56 publications

Potential‐Induced Spin Changes in Fe/N/C Electrocatalysts Assessed by In Situ X‐ray Emission Spectroscopy

Potential‐Induced Spin Changes in Fe/N/C Electrocatalysts Assessed by In Situ X‐ray Emission Spectroscopy

The five-analyzer point-to-point scanning crystal spectrometer at ESRF ID26

Potential‐Induced Spin Changes in Fe/N/C Electrocatalysts Assessed by In Situ X‐ray Emission Spectroscopy

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