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78 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
Optics	An automated and robust method for modelling X-ray beamlines with plane grating monochromators Patrick Yuheng Wang , Murilo Bazan Da Silva , Georg Held , Hongchang Wang , Kawal Sawhney , Andrew C. Walters Journal Of Synchrotron Radiation 32 DOI: 10.1107/S1600577525003200 Open Access Show Abstract ▼ Abstract: The plane grating monochromator (PGM) is an optical instrument used in the majority of soft X-ray beamlines. Despite its ubiquity, the PGM efficiency can easily be overestimated, because the geometry of many modern PGMs can lead to unexpected blocking of the beam. We have developed a new workflow in Python for simulating PGMs, thus extending the capabilities of SHADOW3, a well established ray tracing software tool. We have used our method to simulate the flux on branch C of the Versatile Soft X-ray (VerSoX) beamline B07 at Diamond Light Source. The simulation results demonstrate qualitative agreement with the experimental measurements, confirming the robustness of the proposed methodology.	Jul 2025
E02-JEM ARM 300CF	Inherent structural descriptors via machine learning Emanuele Telari , Antonio Tinti , Manoj Settem , Carlo Guardiani , Lakshmi Kumar Kunche , Morgan Rees , Henry Hoddinott , Malcolm Dearg , Bernd Von Issendorff , Georg Held , Thomas Slater , Richard E. Palmer , Luca Maragliano , Riccardo Ferrando , Alberto Giacomello Reports On Progress In Physics DOI: 10.1088/1361-6633/add95b Diamond Proposal Number(s): [28449] Open Access Show Abstract ▼ Abstract: Finding proper collective variables for complex systems and processes is one of the most challenging tasks in simulations, which limits the interpretation of experimental and sim- ulated data and the application of enhanced sampling techniques. Here, we propose a machine learning approach able to distill few, physically relevant variables by associating instantaneous configurations of the system to their corresponding inherent structures as defined in liquids theory. We apply this approach to the challenging case of structural tran- sitions in nanoclusters, managing to characterize and explore the structural complexity of an experimentally relevant system constituted by 147 gold atoms. Our inherent-structure variables are shown to be e!ective at computing complex free-energy landscapes, transi- tion rates, and at describing non-equilibrium melting and freezing processes. In addition, we illustrate the generality of this machine learning strategy by deploying it to understand conformational rearrangements of the bradykinin peptide, indicating its applicability to a vast range of systems, including liquids, glasses, and proteins.	May 2025
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS E01-JEM ARM 200CF E02-JEM ARM 300CF I20-EDE-Energy Dispersive EXAFS (EDE)	Tuning the selectivity of NH3 oxidation via cooperative electronic interactions between platinum and copper sites Lu Chen , Xuze Guan , Zhaofu Fei , Hiroyuki Asakura , Lun Zhang , Zhipeng Wang , Xinlian Su , Zhangyi Yao , Luke L. Keenan , Shusaku Hayama , Matthijs A. Van Spronsen , Burcu Karagoz , Georg Held , Christopher S. Allen , David G. Hopkinson , Donato Decarolis , June Callison , Paul J. Dyson , Feng Ryan Wang Nature Communications 16 DOI: 10.1038/s41467-024-54820-y Diamond Proposal Number(s): [30622, 33257, 31922] Open Access Show Abstract ▼ Abstract: Selective catalytic oxidation (SCO) of NH3 to N2 is one of the most effective methods used to eliminate NH3 emissions. However, achieving high conversion over a wide operating temperature range while avoiding over-oxidation to NOx remains a significant challenge. Here, we report a bi-metallic surficial catalyst (PtSCuO/Al2O3) with improved Pt atom efficiency that overcomes the limitations of current catalysts. It achieves full NH3 conversion at 250 °C with a weight hourly space velocity of 600 ml NH3·h−1·g−1, which is 50 °C lower than commercial Pt/Al2O3, and maintains high N2 selectivity through a wide temperature window. Operando XAFS studies reveal that the surface Pt atoms in PtSCuO/Al2O3 enhance the redox properties of the Cu species, thus accelerating the Cu2+ reduction rate and improving the rate of the NH3-SCO reaction. Moreover, a synergistic effect between Pt and Cu sites in PtSCuO/Al2O3 contributes to the high selectivity by facilitating internal selective catalytic reduction.	Jan 2025
	Structure determination by low-energy electron diffraction - A roadmap to the future Georg Held Surface Science 30 DOI: 10.1016/j.susc.2025.122696 Show Abstract ▼ Abstract: Of all experimental Surface Science techniques, LEED-IV surface crystallography delivers the most complete set of crystallographic data for the near-surface regions (down to Å below the surface) of ordered single crystal surfaces. In the last five decades a large number of surface structures have been determined but theoretical and experimental procedures need to be adopted to meet the requirements of new directions in Surface Science. In this perspective article approaches will be discussed for extracting structural information from disordered and rough surfaces, increasing the experimental data set for large unit cells with complex unit cells, improving the scattering potentials used to calculate LEED-IV curves, and expanding the pressure range of the technique.	Jan 2025
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS	Operando characterization of electrochemistry at the rutile TiO2(110)/0.1 M HCl interface using ambient pressure XPS Jiangdong Yu , Conor Byrne , Jameel Imran , Zoe Henderson , Katherine B. Holt , Alexander I. Large , Georg Held , Alex Walton , Geoff Thornton The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.4c07173 Diamond Proposal Number(s): [26045] Open Access Show Abstract ▼ Abstract: Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) was employed to investigate the effect of applied potential on the interface of TiO2(110) with 0.1 M HCl. The study, which involved operando electrochemical characterization, enabled real-time monitoring and analysis of electrochemical processes. There is a significant influence on the interface composition; in particular, the surface Cl– surface coverage varies with electrochemical potential. Moreover, there appears to be a reaction of evolved Cl with adventitious carbon to form C–Cl and C–Cl2 species.	Nov 2024
I06-Nanoscience (XPEEM)	Atomic structure of different surface terminations of polycrystalline ZnPd M. Lowe , A. Al-Mahboob , D. Ivarsson , M. Armbrüster , J. Ardini , G. Held , F. Maccherozzi , A. Bayer , V. Fournee , J. Ledieu , J. T. Sadowski , R. Mcgrath , H. R. Sharma Physical Review Materials 8 DOI: 10.1103/PhysRevMaterials.8.105801 Open Access Show Abstract ▼ Abstract: The intermetallic compound ZnPd has been found to have desirable characteristics as a catalyst for the steam reforming of methanol. The understanding of the surface structure of ZnPd is important to optimize its catalytic behavior. However, due to the lack of bulk single-crystal samples and the complexity of characterizing surface properties in the available polycrystalline samples using common experimental techniques, all previous surface science studies of this compound have been performed on surface alloy samples formed through thin-film deposition. In this study, we present findings on the chemical and atomic structure of the surfaces of bulk polycrystalline ZnPd studied by a variety of complementary experimental techniques, including scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), low energy electron microscopy (LEEM), photoemission electron microscopy (PEEM), and microspot low-energy electron diffraction (𝜇-LEED). These experimental techniques, combined with density functional theory (DFT)-based thermodynamic calculations of surface free energy and detachment kinetics at the step edges, confirm that surfaces terminated by atomic layers composed of both Zn and Pd atoms are more stable than those terminated by only Zn or Pd layers. DFT calculations also demonstrate that the primary contribution to the tunneling current arises from Pd atoms, in agreement with the STM results. The formation of intermetallics at surfaces may contribute to the superior catalyst properties of ZnPd over Zn or Pd elemental counterparts.	Oct 2024
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1 I10-Beamline for Advanced Dichroism - scattering	Spinel ferrites MFe2O4 (M = Co, Cu, Zn) for photocatalysis: theoretical and experimental insights Charlotte A. Hall , Pilar Ferrer , David C. Grinter , Santosh Kumar , Ivan Da Silva , Juan Rubio-Zuazo , Peter Bencok , Frank De Groot , Georg Held , Ricardo Grau-Crespo Journal Of Materials Chemistry A 15 DOI: 10.1039/D4TA04941A Diamond Proposal Number(s): [33639, 34919, 36558] Open Access Show Abstract ▼ 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.	Sep 2024
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1	La0.2Sr0.25Ca0.45TiO3 surface reactivity with H2: a combined operando NEXAFS and computational study 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 The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.4c01900 Diamond Proposal Number(s): [33111] Show Abstract ▼ 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.	Aug 2024
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)	Subsurface single-atom catalyst enabled by mechanochemical synthesis for oxidation chemistry 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 Angewandte Chemie International Edition DOI: 10.1002/anie.202410457 Diamond Proposal Number(s): [23759, 24450, 29092, 31852] Open Access Show Abstract ▼ 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.	Jul 2024
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1	Effects of phosphorus doping on amorphous boron nitride’s chemical, sorptive, optoelectronic, and photocatalytic properties 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 The Journal Of Physical Chemistry C 55 DOI: 10.1021/acs.jpcc.4c02314 Diamond Proposal Number(s): [30777] Open Access	Jul 2024

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