B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
I09-Surface and Interface Structural Analysis
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Nickil
Shah
,
Galo J.
Paez Fajardo
,
Hrishit
Banerjee
,
Gaurav C.
Pandey
,
Ashok S.
Menon
,
Muhammad
Ans
,
Veronika
Majherova
,
Gerard
Bree
,
Satish
Bolloju
,
David .
Grinter
,
Pilar
Ferrer
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Melanie
Loveridge
,
Andrew J.
Morris
,
Clare P.
Grey
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[30201, 33459]
Open Access
Abstract: In Ni-rich layered oxide cathodes, cycling above the oxygen-loss threshold voltage (∼4.3 V vs Li+/Li) promotes structural transformations at the cathode surface. These transformations can result in various thermodynamically favorable rocksalt-like (RSL) structures (NiO, NiOx, and/or LiyNizO) that have different Li+ transport properties. Elucidating the precise phase type in the RSL can help determine design strategies to improve Li+ kinetics and identify design rules to suppress capacity fade in Ni-rich cathodes. This study utilizes surface-sensitive X-ray absorption spectroscopy in combination with first-principles simulations and distinguishes the layered oxide spectroscopic features from those of surface-reduced layers of pure NiO and LixNi1–xO. The transport of lithium ions through this oxygen-loss-induced surface-reconstructed layer is studied with operando X-ray diffraction in a pouch cell as a function of cycling aging and constant voltage protocols.
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Feb 2025
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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-B1-Versatile Soft X-ray beamline: High Throughput ES1
I10-Beamline for Advanced Dichroism - scattering
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Diamond Proposal Number(s):
[33639, 34919, 36558]
Open Access
Abstract: Spinel ferrites exhibit significant promise in photocatalysis and other applications due to their compositional diversity and favourable electronic structure, magnetism, and partially tuneable cation distribution. However, their complex properties, for example, the different behaviour of bulk and nanostructured materials, are not well understood. Here, we combine advanced computational and experimental methods with reactivity measurements to explore the inversion degrees, electronic structures, and photocatalytic activities of MFe2O4 spinels (M = Co, Cu, Zn). X-ray diffraction and anomalous X-ray scattering measurements determined bulk inversion degrees of 0.81, 0.91, and 0.26 for CoFe2O4, CuFe2O4, and ZnFe2O4, respectively. Photocatalytic tests showed that only ZnFe2O4 is active in the oxygen evolution reaction (OER), which correlates with its favourable band alignment, as determined through electronic structure simulations. Surface-sensitive X-ray Absorption Spectroscopy (XAS) measurements provided insights into the cation distributions at the surfaces, showing significant deviations from bulk properties, particularly in ZnFe2O4 in which 52% of the near-surface tetrahedral sites are occupied by Fe cations, compared to 26% in the bulk. DFT simulations of ZnFe2O4 illustrated how the surface terminations can alter the thermodynamic preference for cation distribution in comparison with the bulk. Our findings illustrate the complex interplay between surface and bulk properties in spinel ferrites.
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Sep 2024
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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F.
Bassato
,
S.
Mauri
,
L.
Braglia
,
A. Yu.
Petrov
,
E.
Dobovičnik
,
F.
Tavani
,
A.
Tofoni
,
P.
Ferrer
,
D.
Grinter
,
G.
Held
,
P.
D'Angelo
,
P.
Torelli
Diamond Proposal Number(s):
[33111]
Abstract: A-site doped SrTiO3 is considered as a promising substitute for traditional anodic metals in solid oxide fuel cells (SOFCs). In this study, we present the reactivity of La0.2Sr0.25Ca0.45TiO3 (LCSTO), La0.2Sr0.7TiO3 (LSTO), and SrTiO3 (STO) toward H2 by operando ambient pressure NEXAFS spectroscopy and theoretical spectra simulation with FDMNES code. The samples were synthesized by MBE (molecular beam epitaxy), hydrothermal, and modified-Pechini routes. We found that the reducibility of the samples depends not only on their stoichiometry but also on the morphology, which is determined by the synthetic method. The results of these experiments give insight into the reducibility of Ti4+ in perovskites as well as the opportunity to further optimize the synthesis of these materials to obtain the best performance for SOFC applications.
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Aug 2024
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Frances K.
Towers Tompkins
,
Lewis G.
Parker
,
Richard M.
Fogarty
,
Jake M.
Seymour
,
Ekaterina
Gousseva
,
David C.
Grinter
,
Robert G.
Palgrave
,
Christopher D.
Smith
,
Roger A.
Bennett
,
Richard P.
Matthews
,
Kevin R. J.
Lovelock
Diamond Proposal Number(s):
[29413, 30367, 31939, 33378, 35207]
Open Access
Abstract: X-ray photoelectron spectroscopy (XPS) and ab initio calculations show that fully alkylated onium cation electronic structure can be tuned using both the alkyl chains and the central onium atom. The key for tuning the central onium atom is methyl versus longer alkyl chains, allowing selection of the optimum cation for a wide range of applications, including catalysis and biocides.
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Aug 2024
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Ioanna
Itskou
,
Andreas
Kafizas
,
Irena
Nevjestic
,
Soranyel
Gonzalez Carrero
,
David C.
Grinter
,
Hassan
Azzan
,
Gwilherm
Kerherve
,
Santosh
Kumar
,
Tian
Tian
,
Pilar
Ferrer
,
Georg
Held
,
Sandrine
Heutz
,
Camille
Petit
Diamond Proposal Number(s):
[30777]
Open Access
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Jul 2024
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Poting
Liu
,
Anna
Makarova
,
Katharina
Freiberg
,
David C.
Grinter
,
Divanshu
Sharma
,
Pilar
Ferrer
,
Olga
Chuvenkova
,
Tanja
Deckert‐gaudig
,
Sergey
Turishchev
,
Stephanie
Lippmann
,
Vladimir
Sivakov
Diamond Proposal Number(s):
[33956]
Abstract: Here, a phenomenon of efficient oxygen exchange between a silicon surface and a thin layer of tin dioxide during chemical vapor deposition is presented, which leads to a unique Sn:SiO2 layer. Under thermodynamic conditions in the temperature range of 725–735 °C, the formation of nanostructures with volcano-like shapes in “active” and “dormant” states are observed. Extensive characterization techniques, such as electron microscopy, X-ray diffraction, synchrotron radiation-based X-ray photoelectron, and X-ray absorption near-edge structure spectroscopy, are applied to study the formation. The mechanism is related to the oxygen retraction between tin(IV) oxide and silicon surface, leading to the thermodynamically unstable tin(II)oxide, which is immediately disproportionate to metallic Sn and SnO2 localized in the SiO2 matrix. The diffusion of metallic tin in the amorphous silicon oxide matrix leads to larger agglomerates of nanoparticles, which is similar to the formation of a magma chamber during the natural volcanic processes followed by magma eruption, which here is associated with the formation of depressions on the surface filled with metallic tin particles. This new effect contributes a new approach to the formation of functional composites but also inspires the development of unique Sn:SiO2 nanostructures for diverse application scenarios, such as thermal energy storage.
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Jul 2024
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[37075]
Open Access
Abstract: X-ray photoelectron spectroscopy based on synchrotron radiation was used to investigate the composition of the observed SnO2-x/Sn:SiO2-x thin layer grown by organometallic chemical vapour deposition on single-crystalline silicon wafer with additional argon ions etching treatment. Due to the formation of a thermodynamic anomaly during in situ layer growth, an efficient oxygen exchange between silicon and tin oxide phases occurs. The present study addresses the effect of localized surface charging and its influence on the obtained XPS core level spectra. We found that due to the high electrical conductivity of metallic tin and the direct coupling of tin particles to the silicon wafer, the XPS Sn 3d5/2 core level spectrum is not affected by the surface charge compared to the highly charged dielectric silicon oxide matrix, as observed for the XPS O 1 s and Si 2p core level spectra. Our results show that the core level spectra of Si 2p and O 1 s are shifted up to 3 eV due to the presence of uncompensated positive charge on the surface of the silica matrix. These results provide insight into the influence of surface charge effects on the analysis of conductor/insulator composite materials and contribute to the application of Sn-based materials in various application concepts related to energy and surface functionalization.
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Jun 2024
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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Diamond Proposal Number(s):
[32763, 33640]
Open Access
Abstract: Suitable reaction cells are critical for operando near ambient pressure (NAP) soft X-ray photoelectron spectroscopy (XPS) and Near-edge X-ray absorption fine structure (NEXAFS) studies. They enable tracking the chemical state and structural properties of catalytically active materials under realistic reaction conditions, and thus allow a better understanding of charge transfer at the liquid-solid interface, activation of reactant molecules, and surface intermediate species. In order to facilitate such studies, we have developed a top-side illuminated operando spectro-electrochemical flow cell for synchrotron-based NAP-XPS and NEXAFS studies. Our modular design uses a non-metal (PEEK) body, and replaceable membranes which can be either of X-ray transparent silicon nitride (SiNx) or of water permeable polymer membrane materials (e.g., NafionTM). The design allows rapid sample exchange and simultaneous measurements of total electron yield (TEY), Auger electron yield (AEY) and fluorescence-yield (TFY). The developed system is highly modular and can be used in the laboratory or directly at the beamline for operando XPS/ X-ray absorption spectroscopy (XAS) investigations of surfaces and interfaces. We present examples to demonstrate the capabilities of the cell. These include an operando NEXAFS study of the Cu-redox chemistry using a SiNx membrane/Ti-Au/ Cu working electrode assembly (WEA) and a NAP-XPS and -NEXAFS study of water adsorption on a NafionTM polymer membrane based working electrode assembly (NafionTM/C/IrOx catalyst).
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Jun 2024
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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David C.
Grinter
,
Pilar
Ferrer
,
Federica
Venturini
,
Matthijs A.
Van Spronsen
,
Alexander I.
Large
,
Santosh
Kumar
,
Maximilian
Jaugstetter
,
Alex
Iordachescu
,
Andrew
Watts
,
Sven L. M.
Schroeder
,
Anna
Kroner
,
Federico
Grillo
,
Stephen M.
Francis
,
Paul B.
Webb
,
Matthew
Hand
,
Andrew
Walters
,
Michael
Hillman
,
Georg
Held
Open Access
Abstract: The beamline optics and endstations at branch B of the Versatile Soft X-ray (VerSoX) beamline B07 at Diamond Light Source are described. B07-B provides medium-flux X-rays in the range 45–2200 eV from a bending magnet source, giving access to local electronic structure for atoms of all elements from Li to Y. It has an endstation for high-throughput X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) measurements under ultrahigh-vacuum (UHV) conditions. B07-B has a second endstation dedicated to NEXAFS at pressures from UHV to ambient pressure (1 atm). The combination of these endstations permits studies of a wide range of interfaces and materials. The beamline and endstation designs are discussed in detail, as well as their performance and the commissioning process.
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May 2024
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