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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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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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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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[28477]
Abstract: Dry plant matter (biomass) is an abundantly available raw material for the production of biofuels. The principal carbohydrate polymer it contains, cellulose, is packed with glucose units that can be fermented into bioethanol - a sustainable liquid fuel. These polymers are difficult to break down chemically, but we get a helping hand from the natural enzymes that have evolved to do the job. Widely found enzymes, lytic polysaccharide monooxygenases (LPMOs), are major contributors to natural carbon recycling and are now used in commercial bioethanol production. However, questions remain around how these enzymes survive the powerful chemistry they wield. In work recently published in the Journal of the American Chemical Society, researchers from the University of Manchester, Novozymes, Graz University of Technology, the University of York and Diamond Light Source, used a combination of stopped-flow spectroscopy, targeted mutagenesis, TD-DFT calculations, electron paramagnetic resonance spectroscopy and High Energy Resolution Fluorescence Detection X-ray Absorption Spectroscopy (HERFD−XAS) to investigate how these oxidative enzymes protect themselves from harmful side reactions. Their results show that short-lived molecules produced during the breakdown of polysaccharides provide a built-in defence and repair mechanism.
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Dec 2023
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[19013]
Open Access
Abstract: The oxygen storage capacity of ceria-based catalytic materials is influenced by their size, morphology, and surface structure, which can be tuned using surfactant-mediated synthesis. In particular, the cuboidal morphology exposes the most reactive surfaces; however, when the capping agent is removed, the nanocubes can agglomerate and limit the available reactive surface. Here, we study ceria nanocubes, lanthanum-doped ceria nanocubes, and ceria nanocubes embedded inside a highly porous silica aerogel by high-energy resolution fluorescence detection─X-ray absorption near edge spectroscopy at the Ce L3 edge. In situ measurements showed an increased reversibility of redox cycles in ceria nanocubes when embedded in the aerogel, demonstrating enhanced reactivity due to the retention of reactive surfaces. These aerogel nanocomposites show greater improvement in the redox capacity and increased thermal stability of this catalytic material compared to the surfactant-capped nanocubes. Ex situ measurements were also performed to study the effect of lanthanum doping on the cerium oxidation state in the nanocubes, indicating a higher proportion of Ce4+ compared to that of the undoped ceria nanocubes.
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Sep 2023
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Jingming
Zhao
,
Ying
Zhuo
,
Daniel E.
Diaz
,
Muralidharan
Shanmugam
,
Abbey J.
Telfer
,
Peter J.
Lindley
,
Daniel
Kracher
,
Takahiro
Hayashi
,
Lisa S.
Seibt
,
Florence J.
Hardy
,
Oliver
Manners
,
Tobias M.
Hedison
,
Katherine A.
Hollywood
,
Reynard
Spiess
,
Kathleen M.
Cain
,
Sofia
Diaz-Moreno
,
Nigel S.
Scrutton
,
Morten
Tovborg
,
Paul H.
Walton
,
Derren J.
Heyes
,
Anthony P.
Green
Diamond Proposal Number(s):
[28477]
Open Access
Abstract: Oxygenase and peroxygenase enzymes generate intermediates at their active sites which bring about the controlled functionalization of inert C–H bonds in substrates, such as in the enzymatic conversion of methane to methanol. To be viable catalysts, however, these enzymes must also prevent oxidative damage to essential active site residues, which can occur during both coupled and uncoupled turnover. Herein, we use a combination of stopped-flow spectroscopy, targeted mutagenesis, TD-DFT calculations, high-energy resolution fluorescence detection X-ray absorption spectroscopy, and electron paramagnetic resonance spectroscopy to study two transient intermediates that together form a protective pathway built into the active sites of copper-dependent lytic polysaccharide monooxygenases (LPMOs). First, a transient high-valent species is generated at the copper histidine brace active site following treatment of the LPMO with either hydrogen peroxide or peroxyacids in the absence of substrate. This intermediate, which we propose to be a CuII–(histidyl radical), then reacts with a nearby tyrosine residue in an intersystem-crossing reaction to give a ferromagnetically coupled (S = 1) CuII–tyrosyl radical pair, thereby restoring the histidine brace active site to its resting state and allowing it to re-enter the catalytic cycle through reduction. This process gives the enzyme the capacity to minimize damage to the active site histidine residues “on the fly” to increase the total turnover number prior to enzyme deactivation, highlighting how oxidative enzymes are evolved to protect themselves from deleterious side reactions during uncoupled turnover.
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Sep 2023
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[30309]
Open Access
Abstract: Understanding the effects of high energy neutron damage on REBa2Cu3O$_{7-\delta}$ (REBCO) coated conductor is of vital importance for the design of the magnetic confinement systems for compact nuclear fusion power plants. However, neutron irradiation campaigns can only be carried out in a few facilities, and the experiments are very slow and expensive partly because the samples become radioactive. Ion irradiation provides an easily accessible alternative route to studying the effects of radiation on high temperature superconductors, which not only increases the volume of technical data that can be obtained but also enables more complex experiments such as in situ cryogenic irradiation. The question is, does ion damage offer a good proxy for neutrons? Here we use high energy resolution fluorescence detected x-ray absorption spectroscopy to probe the effects of fast neutron irradiation on the local environment around the copper ions in the REBCO layer of coated conductor tapes. We find that the spectral changes are similar to those induced by helium ion irradiation, suggesting that both projectiles produce the same types of structural defect in the REBCO lattice, although there is some evidence of an additional type of defect present in the sample heavily damaged by He+ ion irradiation. It is also shown that the linear degradation of superconducting transition temperature (Tc) of coated conductors with the calculated number of displacements per atom occurs at the same rate for neutrons and helium ions. Together these results provide new evidence suggesting that helium ions can emulate neutron point defect damage in REBCO high temperature superconductor reasonably well, increasing confidence that helium ions could be used as a useful proxy for neutrons in future experiments.
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Aug 2023
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