I20-Scanning-X-ray spectroscopy (XAS/XES)
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Biao
He
,
Pouya
Hosseini
,
Daniel
Escalera-López
,
Jonas
Schulwitz
,
Olaf
Rudiger
,
Ulrich
Hagemann
,
Markus
Heidelmann
,
Serena
Debeer
,
Martin
Muhler
,
Serhiy
Cherevko
,
Kristina
Tschulik
,
Tong
Li
Diamond Proposal Number(s):
[28433]
Open Access
Abstract: An atomic-scale understanding of how electrocatalyst surfaces reconstruct and transform during electrocatalytic reactions is essential for optimizing their activity and longevity. This is particularly important for the oxygen evolution reaction (OER), where dynamic and substantial structural and compositional changes occur during the reaction. Herein, a multimodal method is developed by combining X-ray fine structure absorption and photoemission spectroscopy, transmission electron microscopy, and atom probe tomography with electrochemical measurements to interrogate the temporal evolution of oxidation states, atom coordination, structure, and composition on Co2MnO4 and CoMn2O4 cubic spinel nanoparticle surfaces upon OER cycling in alkaline media. Co2MnO4 is activated at the onset of OER due to the formation of ≈2 nm Co-Mn oxyhydroxides with an optimal Co/Mn ratio of ≈3. As OER proceeds, Mn dissolution and redeposition occur for the CoMn oxyhydroxides, extending the OER stability of Co2MnO4. Such dynamic dissolution and redeposition are also observed for CoMn2O4, leading to the formation of less OER-active Mn-rich oxides on the nanoparticle surfaces. This study provides mechanistic insights into how dynamic surface reconstruction and transformation affect the activity and stability of mixed CoMn cubic spinels toward OER.
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Oct 2024
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Yuvraj
Vaishnav
,
Rohit K.
Rai
,
Walid
Al Maksoud
,
Fumitaka
Takeiri
,
Shusaku
Hayama
,
Hiroshi
Yaguchi
,
Samy
Ould-Chikh
,
Marcell
Toth
,
Raza Ullah Shah
Bacha
,
Bambar
Davaasuren
,
Maxim
Avdeev
,
Genki
Kobayashi
,
Yoji
Kobayashi
Diamond Proposal Number(s):
[31497]
Abstract: High-entropy materials have gained significant interest in many applications, but structural investigations of the effect on anions in the crystal structure are still scarce. Here, we study the effect of multicomponent cation disorder in the case of mixed-anion compounds. The distribution of mixed anions among various coordination sites is important given their implications for properties such as ionic conductivity and bulk diffusion in catalysis. Structural analysis in the fluorite-type (La,Ce,Pr,Nd,Y)H1.5O0.75 reveals that the disordered cationic effects create new interstitial sites, occupied selectively by hydride despite oxide and hydride disorder in other compositions and sites. In contrast, single-lanthanide oxyhydrides of analogous anion content, such as LaH1.5O0.75, or SmH2O0.5 lack the complex interstitial structure. Hydride ion conductivity measurements and bond valence sum energy maps show a considerably low activation energy of hydride migration due to the additional interstitial sites induced by high entropy. Such interstitials can be crucial in applications that involve hydride ion diffusion, such as ammonia synthesis catalysis and solid-state ionics, as further high-entropy compositions are explored.
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Oct 2024
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[29024]
Open Access
Abstract: Reversible anion binding to lanthanide complexes in aqueous solution has emerged as an effective method for anion sensing. Through careful design of the organic ligand, luminescent lanthanide complexes capable of binding biologically relevant anions in a bidentate or monodentate manner can be realized. While single-crystal X-ray diffraction analyses and NMR spectroscopy have revealed the structural geometry of several host–guest complexes, the challenge remains in designing preorganized lanthanide receptors with enhanced anion selectivity for broader applications in diagnostics and bioimaging. To address this challenge, innovative and complementary methods to investigate host-anion binding geometry are becoming increasingly important. Herein, we demonstrate the combined use of Eu L3-edge extended X-ray absorption fine structure (EXAFS) and electron paramagnetic resonance (EPR) spectroscopy to elucidate the binding of nucleoside phosphates (ATP, ADP, and AMP) to a cationic lanthanide complex. We establish that ATP unequivocally binds the lanthanide center in a bidentate manner in water, while ADP adopts both bidentate and monodentate modes, and AMP binds in a monodentate manner. This interdisciplinary approach provides deeper insight into lanthanide host–guest chemistry in solution, laying the groundwork for designing emissive probes that undergo specific anion-induced structural changes and elicit desired optical responses upon binding.
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Oct 2024
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
I10-Beamline for Advanced Dichroism - scattering
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Lijin
An
,
Ruomu
Zhang
,
Prvanin N.
Didwal
,
Michael W.
Fraser
,
Leanne A. H.
Jones
,
Conor M. E.
Phelan
,
Namrata
Ramesh
,
Grant
Harris
,
Robert S.
Weatherup
,
Jack E. N.
Swallow
,
Peixi
Cong
,
Andrey
Poletayev
,
Erik
Bjorklund
,
Christophe J.
Sahle
,
Pilar
Ferrer
,
David C.
Grinter
,
Peter
Bencok
,
Shusaku
Hayama
,
Saiful
Islam
,
Robert
House
,
Peter D.
Nellist
,
Robert J.
Green
,
Rebecca J.
Nicholls
Diamond Proposal Number(s):
[33283, 33062, 32010]
Open Access
Abstract: Ni-rich layered oxide cathodes can deliver higher energy density batteries, but uncertainties remain over their charge compensation mechanisms and the degradation processes that limit cycle life. Trapped molecular O2 has been identified within LiNiO2 at high states of charge, as seen for Li-rich cathodes where excess capacity is associated with reversible O-redox. Here we show that bulk redox in LiNiO2 occurs by Ni-O rehybridization, lowering the electron density on O sites, but importantly without the involvement of molecular O2. Instead, trapped O2 is related to degradation at surfaces in contact with the electrolyte, and is accompanied by Ni reduction. O2 is removed on discharge, but excess Ni2+ persists forming a reduced surface layer, associated with impeded Li transport. This implicates the instability of delithiated LiNiO2 in contact with the electrolyte in surface degradation through O2 formation and Ni reduction, highlighting the importance of surface stabilisation strategies in suppressing LNO degradation.
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Sep 2024
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
E01-JEM ARM 200CF
I09-Surface and Interface Structural Analysis
I20-EDE-Energy Dispersive EXAFS (EDE)
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Xuze
Guan
,
Rong
Han
,
Hiroyuki
Asakura
,
Bolun
Wang
,
Lu
Chen
,
Jay Hon Cheung
Yan
,
Shaoliang
Guan
,
Luke
Keenan
,
Shusaku
Hayama
,
Matthijs A.
Van Spronsen
,
Georg
Held
,
Jie
Zhang
,
Hao
Gu
,
Yifei
Ren
,
Lun
Zhang
,
Zhangyi
Yao
,
Yujiang
Zhu
,
Anna
Regoutz
,
Tsunehiro
Tanaka
,
Yuzheng
Guo
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[23759, 24450, 29092, 31852]
Open Access
Abstract: Single-atom catalysts have garnered significant attention due to their exceptional atom utilization and unique properties. However, the practical application of these catalysts is often impeded by challenges such as sintering-induced instability and poisoning of isolated atoms due to strong gas adsorption. In this study, we employed the mechanochemical method to insert single Cu atoms into the subsurface of Fe2O3 support. By manipulating the location of single atoms at the surface or subsurface, catalysts with distinct adsorption properties and reaction mechanisms can be achieved. It was observed that the subsurface Cu single atoms in Fe2O3 remained isolated under both oxidation and reduction environments, whereas surface Cu single atoms on Fe2O3 experienced sintering under reduction conditions. The unique properties of these subsurface single-atom catalysts call for innovations and new understandings in catalyst design.
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Jul 2024
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[28859, 30113]
Open Access
Abstract: Here, the novel technique of extended-range high-energy-resolution fluorescence detection (XR-HERFD) has successfully observed the n = 2 satellite in manganese to a high accuracy. The significance of the satellite signature presented is many hundreds of standard errors and well beyond typical discovery levels of three to six standard errors. This satellite is a sensitive indicator for all manganese-containing materials in condensed matter. The uncertainty in the measurements has been defined, which clearly observes multiple peaks and structure indicative of complex physical quantum-mechanical processes. Theoretical calculations of energy eigenvalues, shake-off probability and Auger rates are also presented, which explain the origin of the satellite from physical n = 2 shake-off processes. The evolution in the intensity of this satellite is measured relative to the full Kα spectrum of manganese to investigate satellite structure, and therefore many-body processes, as a function of incident energy. Results demonstrate that the many-body reduction factor S02 should not be modelled with a constant value as is currently done. This work makes a significant contribution to the challenge of understanding many-body processes and interpreting HERFD or resonant inelastic X-ray scattering spectra in a quantitative manner.
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Jul 2024
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[21526]
Open Access
Abstract: A high-flux beamline optimized for non-resonant X-ray emission spectroscopy (XES) in the tender X-ray energy range has been constructed at the BESSY II synchrotron source. The beamline utilizes a cryogenically cooled undulator that provides X-rays over the energy range 2.1 keV to 9.5 keV. This energy range provides access to XES [and in the future X-ray absorption spectroscopy (XAS)] studies of transition metals ranging from Ti to Cu (Kα, Kβ lines) and Zr to Ag (Lα, Lβ), as well as light elements including P, S, Cl, K and Ca (Kα, Kβ). The beamline can be operated in two modes. In PINK mode, a multilayer monochromator (E/ΔE ≃ 30–80) provides a high photon flux (1014 photons s−1 at 6 keV and 300 mA ring current), allowing non-resonant XES measurements of dilute substances. This mode is currently available for general user operation. X-ray absorption near-edge structure and resonant XAS techniques will be available after the second stage of the PINK commissioning, when a high monochromatic mode (E/ΔE ≃ 10000–40000) will be facilitated by a double-crystal monochromator. At present, the beamline incorporates two von Hamos spectrometers, enabling time-resolved XES experiments with time scales down to 0.1 s and the possibility of two-color XES experiments. This paper describes the optical scheme of the PINK beamline and the endstation. The design of the two von Hamos dispersive spectrometers and sample environment are discussed here in detail. To illustrate, XES spectra of phosphorus complexes, KCl, TiO2 and Co3O4 measured using the PINK setup are presented.
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May 2024
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Alessia
Munzone
,
Manon
Pujol
,
Ashish
Tamhankar
,
Chris
Joseph
,
Ievgen
Mazurenko
,
Marius
Réglier
,
Sergio A. V.
Jannuzzi
,
Antoine
Royant
,
Giuseppe
Sicoli
,
Serena
Debeer
,
Maylis
Orio
,
A. Jalila
Simaan
,
Christophe
Decroos
Diamond Proposal Number(s):
[31504]
Abstract: In this paper, we employed a multidisciplinary approach, combining experimental techniques and density functional theory (DFT) calculations to elucidate key features of the copper coordination environment of the bacterial lytic polysaccharide monooxygenase (LPMO) from Serratia marcescens (SmAA10). The structure of the holo-enzyme was successfully obtained by X-ray crystallography. We then determined the copper(II) binding affinity using competing ligands and observed that the affinity of the histidine brace ligands for copper is significantly higher than previously described. UV–vis, advanced electron paramagnetic resonance (EPR), and X-ray absorption spectroscopy (XAS) techniques, including high-energy resolution fluorescence detected (HERFD) XAS, were further used to gain insight into the copper environment in both the Cu(II) and Cu(I) redox states. The experimental data were successfully rationalized by DFT models, offering valuable information on the electronic structure and coordination geometry of the copper center. Finally, the Cu(II)/Cu(I) redox potential was determined using two different methods at ca. 350 mV vs NHE and rationalized by DFT calculations. This integrated approach not only advances our knowledge of the active site properties of SmAA10 but also establishes a robust framework for future studies of similar enzymatic systems.
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May 2024
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B18-Core EXAFS
I15-1-X-ray Pair Distribution Function (XPDF)
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[20060]
Abstract: The modern world relies on high-performance lithium-ion (Li-ion) batteries to power mobile devices and electric-powered vehicles, and for the storage systems needed to ensure continuous supplies of low-carbon energy. Demand for these batteries is increasing, but current cathode materials limit the energy density and dominate the cost. A battery is composed of several elements such as the anode, the cathode and the electrolyte. Investigations are performed to improve all separate elements to increase the properties of a battery. At Diamond, many beamlines are involved in energy storage research.
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May 2024
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Jake M.
Seymour
,
Ekaterina
Gousseva
,
Frances
Towers Tompkins
,
Lewis G.
Parker
,
Najaat O.
Alblewi
,
Coby J.
Clarke
,
Shusaku
Hayama
,
Robert G.
Palgrave
,
Roger A.
Bennett
,
Richard P.
Matthews
,
Kevin R. J.
Lovelock
Diamond Proposal Number(s):
[24305, 28565, 30597]
Open Access
Abstract: Using a combination of liquid-phase experimental X-ray spectroscopy experiments and small-scale calculations we have gained new insights into the speciation of halozincate anions in ionic liquids (ILs). Both core and valence X-ray photoelectron spectroscopy (XPS) were performed directly on the liquid-phase ILs, supplemented by Zn 1s X-ray absorption near edge structure (XANES) spectroscopy. Density functional theory (DFT) calculations were carried out on both 1- and 2- halozincate anions, in both a generalised solvation model SMD (Solvation Model based on Density) and the gas phase, to give XP spectra and total energy differences; time-dependent DFT was used to calculate XA spectra. Speciation judgements were made using a combination of the shape and width of experimental spectra, and visual matches to calculated spectra. For 2- halozincate anions, excellent matches were found between experimental and calculated XP spectra, clearly showing that only 2- halozincate anions were present at all zinc halide mole fraction, x, studied. At specific x (0.33, 0.50, 0.60) only one halozincate anion was present; equilibria of different halozincate anions at those x were not observed. All findings show that chlorozincate anion and bromozincate anion speciation matched at the same x. Based on the results, predictions are made of the halozincate anion speciation for all x up to 0.67. Caution is advised when using differences in calculated total energies obtained from DFT to judge halozincate anion speciation, even when the SMD was employed, as predictions based on total energy differences did not always match the findings from experimental and calculated spectra. Our findings clearly establish that the combination of high-quality experimental data from multiple spectroscopies and a wide range of calculated structures are essential to have high confidence in halozincate anion speciation identification.
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Apr 2024
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