B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
|
Guangmeimei
Yang
,
Wei
Huang
,
Yifeng
Wang
,
Caiwu
Liang
,
Yuxiang
Zhou
,
Santosh
Kumar
,
Pilar
Ferrer Escorihuela
,
Parnia
Navabpour
,
Giuseppe
Sanzone
,
Trevor
Ferris
,
Georg
Held
,
Mark
Turner
,
Sarah J.
Haigh
,
Caterina
Ducati
,
Andreas
Kafizas
,
Reshma
Rao
Diamond Proposal Number(s):
[37550]
Open Access
Abstract: The scarcity of Ir presents a major challenge for scaling up its use as a water oxidation electrocatalyst in proton exchange membrane (PEM) water electrolysers. Developing conductive and stable supports is an effective way to reduce iridium loading while maintaining performance. However, the influence of support conductivity and stability on Ir-based catalytic activity remains poorly understood. The behaviour of the support is often obscured in conventional membrane electrode assembly (MEA) systems because IrOx itself is both highly conductive and exceptionally stable. To decouple support conductivity and passivation effects from the intrinsic conductivity of IrOx, we demonstrate a screening platform by studying a series of Ti-Nb alloy thin films produced by sputter deposition and investigate their performance as supports for IrOx water oxidation electrocatalysts. A range of electrochemical tests including accelerated stress tests (AST) were carried out on these samples, where characterisation techniques, including X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM), demonstrated the in situ formation of passivation layers on these supports during water oxidation. Our results suggest that a ~10 nm oxide passivation layer forms on metallic Ti-based supports. On alloying Nb with Ti metal, a more insulating rutile TiO2 phase forms during water oxidation whereas an anatase TiO2, with higher conductivity, is observed on the pure Ti support. Consequently, although alloying Ti with Nb improves the bulk conductivity, the structure of the oxide passivation layer results in a drastic decrease of conductivity and water oxidation activity. Our results demonstrate the importance of the structure and composition of surface oxide phases formed during water oxidation in controlling the overall stability and conductivity of support materials.
|
Apr 2026
|
|
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B18-Core EXAFS
|
Youli
Yu
,
Yifeng
Wang
,
Hanzhi
Ye
,
Sid
Halder
,
Guangmeimei
Yang
,
Boxi
Ye
,
Santosh
Kumar
,
Georg
Held
,
James R.
Durrant
,
Maria-Magdalena
Titirici
,
Reshma R.
Rao
Diamond Proposal Number(s):
[37550, 39622]
Open Access
Abstract: Glycerol oxidation reaction (GOR) is a promising valorization route to upgrade the biodiesel by-product while coproducing green hydrogen at the cathode in electrolyzers. However, the working mechanism of transition-metal-based catalysts such as Ni(OH)2 remains poorly understood. Here, we employed a multioperando spectroelectrochemical approach combining UV–vis optical spectroscopy, X-ray absorption spectroscopy, and time-resolved stepped-potential spectroscopy to investigate the active oxidizing species and charge-transfer dynamics under OER and GOR conditions. We identified NiOOH (Ni3+) as the active species for GOR, whereas the formation of higher-valent NiOO (Ni4+) species is completely suppressed in the presence of glycerol. The accumulation of surface-adsorbed glycerol molecules is the rate-determining step (τ ∼ 27.9 s at 1.47 VRHE), occurring slower than the intrinsic catalytic step of glycerol reaction (τ ∼ 3.2 s at 1.47 VRHE), which involves oxidation and bond cleavage. In contrast, the kinetics of the OER are significantly slower (τ ∼ 167 s at 1.47 VRHE), resulting in the dominance of GOR and suppression of oxygen evolution in the presence of glycerol. The potential-independent production of formic acid during GOR follows an apparent first-order dependence on NiOOH concentration, suggesting continuous C–C bond cleavage activated by reactive *O species. These findings link oxidizing species with charge-transfer dynamics, providing insight for the rational design of Ni-based catalysts for glycerol and other biomass-derived molecule oxidations.
|
Apr 2026
|
|
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
|
James J. C.
Counter
,
Santosh
Kumar
,
Christopher M.
Zalitis
,
Mark
Clapp
,
Alexander I.
Large
,
David C.
Grinter
,
Matthijs A.
Van Spronsen
,
Pilar
Ferrer
,
Burcu
Karagoz
,
Tugce
Eralp Erden
,
Roger A.
Bennett
,
Georg
Held
Diamond Proposal Number(s):
[32763, 36143, 34260, 39495]
Open Access
Abstract: In situ soft X-ray spectroscopy provides direct insight into the electronic structure of electrocatalysts under realistic reaction conditions but remains technically challenging due to the need to combine aqueous electrochemistry with ultra-high-vacuum detection. Here, we present a mesoporous carbon–membrane working electrode assembly (WEA) that enables window-free in situ XPS and NEXAFS measurements during electrochemical reactions. The design integrates a Nafion proton-exchange membrane with a mesoporous carbon–ionomer contact layer and a thin IrOx catalyst layer, providing continuous electronic and protonic pathways and stable hydration through the membrane. By tuning the chamber water vapor pressure to 8 mbar, the WEA maintains a nanometer-thin water layer sufficient for the oxygen evolution reaction (OER) while preserving photoelectron detection efficiency. A robust peristaltic pump integrated with an alumina-bed water vapor dosing system maintains steady-state hydration at 6–10 mbar with <±0.1 mbar variation, enabling reproducible in situ spectra over extended periods. In situ Ir 4f and O 1s XPS reveal oxidation of Ir3+/Ir4+ to Ir4+/Ir5+ and dynamic changes in hydroxyl and lattice oxygen species, while O K-edge NEXAFS identify the formation of potential-stabilized μ2–O and μ1–O oxygen ligand species at OER. The WEA thus provides a quantitative, window-free platform for probing electrochemical interfaces under near-ambient conditions and establishes a general methodology for in situ soft X-ray studies of functional electrocatalysts, closely resembling the architecture and operation of industrial membrane-based water electrolyzers. This approach establishes a reliable methodology for coupling electrochemistry with the element specific soft X-ray spectroscopy under realistic reaction conditions.
|
Mar 2026
|
|
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
E01-JEM ARM 200CF
|
Alexander I.
Large
,
Henry
Hoddinott
,
Haamidah
Sana
,
Elizabeth
Jones
,
James J. C.
Counter
,
Matthijs
Van Spronsen
,
Santosh
Kumar
,
David C.
Grinter
,
Pilar
Ferrer
,
Bernd
Von Issendorff
,
Richard Edward
Palmer
,
Georg
Held
Diamond Proposal Number(s):
[29320, 29935, 33291]
Open Access
Abstract: The importance of cluster-size eects in heterogeneous catalysis is now well recognized. X-ray photoelectron spectroscopy (XPS) is an obvious technique to study size-dependent changes in the chemical composition and electronic structure of catalyst nanoparticles. However, as XPS is an averaging technique based on the detection of electrons, experiments require a narrow distribution of cluster size and a conducting homogeneous support in order to avoid sample charging, which would prevent accurate measurements of chemical shifts. Traditional methods of catalyst synthesis by impregnation/calcination of support powders lead to very large particle size distributions (typically ± 50 %) and insulating samples. They therefore fail both of the above criteria and make it extremely dicult to extract precise sample characterisation. Here we present an alternative approach designed to enable XPS analysis in vacuum and under reaction conditions, whereby: (i) nanoparticles are synthesized by gas condensation and passed through a mass filter, which allows size selection in the range of 1 to 10000 atoms with typically ±4% accuracy; (ii) these particles are deposited onto a thin Al2O3 film grown on Al foil, which mimics the properties of conventional alumina supports while being conductive enough to avoid any charging-related artefacts in the XPS spectra. In vacuum, size-dependent Pd 3d binding-energy shifts up to 1.65 eV were recorded for supported Pd nanoparticles. Changes in the chemical composition of Pd nanoparticles were studied by near-ambient pressure (NAP)-XPS under dry and wet reaction conditions for methane oxidation (CH4 + O2 [+ H2O]) in the temperature range between 150 ◦C and 450 ◦C. Under dry reaction conditions large Pd particles appeared to oxidise almost fully to Pd(II), whereas smaller clusters showed a mix of Pd(0) and Pd(II) oxidation states. Under wet conditions, oxidation starts at lower temperatures and particles of all sizes were fully oxidised when the highest temperature was reached. Sintering during the temperature ramp cannot be excluded, especially for the smaller particles, and may be part of the reason for the dierent behaviour under wet conditions. This study clearly shows composition changes which are particle-size dependent and demonstrate.
|
Mar 2026
|
|
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B18-Core EXAFS
|
Caiwu
Liang
,
Lucas
Garcia Verga
,
Benjamin
Moss
,
Santosh
Kumar
,
Soren B.
Scott
,
Mark A.
Turner
,
Pilar
Ferrer
,
Veronica
Celorrio
,
David C.
Grinter
,
Yemin
Tao
,
Sid
Halder
,
Yifeng
Wang
,
Cindy
Tseng
,
Guangmeimei
Yang
,
Georg
Held
,
Sarah J.
Haigh
,
Aron
Walsh
,
Ifan E. L.
Stephens
,
James R.
Durrant
,
Reshma R.
Rao
Diamond Proposal Number(s):
[34803, 30396, 31886]
Open Access
Abstract: Oxidation states underpin the understanding of active states, reaction mechanisms and catalytic performance of electrocatalysts. However, determining them at complex solid–liquid interfaces is challenging. Here we use multimodal spectroscopy to investigate polarized iridium oxide (IrOx) electrodes, a model water oxidation catalyst, to identify potential-dependent iridium and oxygen oxidation states. By integrating multiple operando spectroscopies (optical (ultraviolet–visible), Ir L-edge and O K-edge X-ray absorption spectroscopy) with electrochemistry mass spectrometry and density functional theory calculations, we identify the sequential depletion of electron densities from the Ir5d band (corresponding to Ir3+→Ir4+→Ir5+), followed by electron removal from the O2p band, forming electrophilic oxygen species (O−1) due to enhanced Ir–O covalency and electronic state overlap. Time-resolved measurements reveal distinct lifetimes for Ir5+ and O−1 states under water oxidation conditions, Ir5+ remains unreactive whereas O−1 is consumed at a time constant commensurate with the reaction rate, indicating that O−1 drives the oxygen evolution reaction. These findings demonstrate the necessity of using multiple operando techniques to gain a unified understanding of the evolution of oxidation states and active sites with potential for water oxidation on oxide catalysts.
|
Feb 2026
|
|
|
|
Abstract: The adsorption geometry of the planar 3, 4, 9, 10-perylene-tetracarboxylic-dianhydride (PTCDA) molecule in the commensurate c(8×8) structure on Ag(100) was determined from the analysis of the intensities in low-energy electron diffraction (LEED-IV). Using data from different angles of incidence and optimized computer code, we were able to overcome earlier challenges given by the limitations of the experimental data set and the calculation times required for the large unit cell with many atoms. Testing of different structures confirmed the on-top adsorption site for the center of the perylene core. The final Pendry 𝑅factor of 𝑅P=0.180 for the on-top position is significantly lower than the one for the fourfold hollow position (minimum 𝑅P=0.369) that is hence excluded. The molecule shows archlike deformation with a downshift of the terminal carboxylic groups. Both the molecular structure and the adsorption height are in very good agreement with results from an earlier normal incidence x-ray standing wave (NIXSW) experiment and new density functional theory (DFT) calculations, which we performed in parallel for 0 K and in addition for 300 K. The LEED-IV analysis demonstrates that the PTCDA induces a relaxation (−0.08versus −0.04Å of the clean surface) and buckling (0.33 Å) of the topmost Ag layer. Special attention was given to the Ag atom below the central ring of the PTCDA. The IV analysis was rather insensitive to its vertical position, and a small 𝑅 factor, close to the minimal, was also obtained when this Ag atom was moved upward (𝑅P=0.185) or even an Ag vacancy site (𝑅P=0.171) was assumed. However, these structures could be excluded on the basis of DFT calculations. The vacancy structure has a free adsorption energy that is 0.18 eV larger compared to the favored geometry where this central Ag atom is pushed downward, partly due to the energy cost for the vacancy formation. The discussion of adsorbate-induced formation of vacancy sites is important because it was reported for C60 on Ag(111). The up- and downward displacements of the first-layer Ag atoms support the understanding of the chemical bond of the PTCDA to the Ag substrate and reveal how the originally planar 𝜋 system is locally distorted. Our analysis proves that LEED-IV is a powerful technique for surface crystallography of large organic adsorbates.
|
Feb 2026
|
|
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
|
Diamond Proposal Number(s):
[34919, 37955]
Open Access
Abstract: A combination of experimental methods and computational techniques have been used to investigate the composition of the zinc ferrite (ZnFe2O4) (1 1 1) single crystal surface under different preparation methods. Surface-sensitive XPS and NEXAFS measurements show that upon annealing in ultra-high vacuum (UHV), Zn depletion occurs, leading to the formation of an iron-rich (1 1 1) surface, whereas annealing in the presence of O2 gas maintains a more bulk-like ZnFe2O4 surface composition. Analysis of the Fe 2p photoemission (XPS) and Fe L edge X-ray absorption signals shows a clear difference in iron oxidation state and distribution between the two different preparation conditions. After annealing in UHV, a mixed Fe2+/Fe3+ oxidation state and a cation distribution like that of a magnetite (Fe3O4) structure is observed, whereas after annealing in oxygen gas only Fe3+, mostly in octahedral coordination, is observed, as expected for a ZnFe2O4 structure. Temperature-dependent XPS confirms significant Zn depletion in the near-surface region above 500 °C under UHV, with almost no Zn remaining at 600 °C; under an O2 atmosphere no zinc depletion is observed up to 600 °C. A theoretical model based on DFT simulations illustrates how reduction from ZnFe2O4 to Fe3O4 with formation of O2 and Zn gas is thermodynamically feasible under UHV conditions, whereas the same reaction is not favourable at higher oxygen partial pressures. Our findings demonstrate the strong impact that UHV treatment has on zinc ferrite surfaces, and cautions that UHV environments, routinely employed for surface analysis, can themselves induce substantial modifications to the surface, thereby complicating the interpretation of measurements in the context of catalytically relevant conditions.
|
Dec 2025
|
|
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
E01-JEM ARM 200CF
I20-Scanning-X-ray spectroscopy (XAS/XES)
|
Lu
Chen
,
Xuze
Guan
,
Zhangyi
Yao
,
Shusaku
Hayama
,
Matthijs A.
Van Spronsen
,
Burcu
Karagoz
,
Georg
Held
,
David G.
Hopkinson
,
Christopher S.
Allen
,
June
Callison
,
Paul J.
Dyson
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[30576, 31867, 32996]
Open Access
Abstract: Tuning the electronic properties of nanocatalysts via doping with monodispersed hetero-metal atoms is an effective method used to enhance catalytic properties. Doping CuO nanoparticles with monodispersed Co atoms using different reductants affords catalysts (CoBCu/Al2O3 and CoHCu/Al2O3) with strikingly different electronic structures. Compared to CoHCu/Al2O3, the CuO nanoparticles in CoBCu/Al2O3 have longer and weaker Cu-O bonds, with a lower 1s → 4pz antibonding transition and higher 4p → 1s bonding transition (as demonstrated from HERFD-XANES and valence-to-core X-ray emission spectroscopy). The weaker Cu-O bonds in CoBCu/Al2O3 lead to superior redox activity of the CuO nanoparticles, evidenced from operando XAFS and in-situ near ambient pressure-near edge X-ray absorption fine structures studies. Such superior redox properties of CuO in CoBCu/Al2O3 result in a much reduced activation energy of CoBCu/Al2O3 compared to CoHCu/Al2O3 (40.0 vs. 63.5 kJ/mol), thus leading to an enhancement in catalytic performance in the selective catalytic oxidation of NH3 to N2.
|
Oct 2025
|
|
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
Optics
|
Wai Jue
Tan
,
Arindam
Majhi
,
Wadwan
Singhapong
,
Andrew C.
Walters
,
Matthijs A.
Van Spronsen
,
Georg
Held
,
Burcu
Karagoz
,
David C.
Grinter
,
Pilar
Ferrer
,
Guru
Venkat
,
Qiushi
Huang
,
Zhe
Zhang
,
Zhanshan
Wang
,
Patrick Yuheng
Wang
,
Andrey
Sokolov
,
Hongchang
Wang
,
Kawal
Sawhney
Open Access
Abstract: X-ray Photoelectron Spectroscopy (XPS) is a powerful tool for probing the chemical and electronic states of materials with elemental specificity and surface sensitivity. However, its application in the tender X-ray range (1–5 keV) for synchrotron radiation has remained limited due to the limited choice of optics capable of maintaining high reflectivity and efficiency in this energy window. To address this, multilayer (ML) grating structures have become increasingly popular, offering significantly higher efficiency than SL coatings in the tender X-ray region. This paper presents the development of ML laminar gratings optimised for enhancing efficiency in the tender X-ray range, and capable of retaining performance under intense X-ray exposure in the oxygen partial pressure of 10 mbar. The ML coating quality was verified through X-ray reflectivity (XRR), XPS and near-edge X-ray absorption fine structures (NEXAFS) measurements, while the performance of the grating was validated through beamline flux transmission and XPS measurements. The MLLG demonstrated 22 higher intensity in flux and XPS, significantly improving the signal-to-noise ratio. Most importantly, the MLLGs outperformed traditional designs by offering improved spectral resolution while maintaining measurement capability at varying values without compromising the intensity. Furthermore, we demonstrated that the incorporation of nitrogen during deposition further enhances flux transmission.
|
Oct 2025
|
|
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
|
Diamond Proposal Number(s):
[33415, 34976]
Open Access
Abstract: Electro-oxidation is one of the most promising and eco-friendly technologies for water decontamination. However, its industrial application is still limited by the high cost, poor faradaic efficiency, low durability, and potential toxicity of common high-power oxidation anodes. These challenges have been addressed by developing a novel composite comprising a mixed metal oxide (NiMnO3) and reduced graphene oxide (rGO). The NiMnO3–rGO anode allowed the fast and complete removal of phenol. Among different highly porous substrates, graphite felt (GF) led to the highest energy efficiency, since the GF/NiMnO3–rGO anode yielded 100% phenol removal within only 30 min at a current density as low as 10 mA cm−2, which was accompanied by 85% COD removal at 120 min. This anode demonstrated excellent stability, maintaining 100% phenol removal efficiency across five consecutive cycles while also showing low energy consumption (60–65 Wh (kg COD)−1). Operando X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) analysis provided mechanistic insights. It is demonstrated that rGO shifts the ˙OH production pathway towards the lattice oxygen mechanism (LOM), in contrast to the adsorbate evolution mechanism (AEM) observed for NiMnO3 alone. This mechanistic shift supports the enhanced stability and sustained electrocatalytic activity, contributing to the high performance of the GF/NiMnO3–rGO composite anode in the context of a more sustainable technology for treating organic contaminants.
|
Oct 2025
|
|
