B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B18-Core EXAFS
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Yifeng
Wang
,
Eleanor
Ender
,
Santosh
Kumar
,
Cindy
Tseng
,
Guangmeimei
Yang
,
Boxi
Ye
,
Caiwu
Liang
,
Youli
Yu
,
Norton
West
,
Inderjeet
Chauhan
,
Jun H.
Ng
,
Sid
Halder
,
Sang Gu
Ji
,
Georg
Held
,
Mary P.
Ryan
,
Katie L.
Moore
,
Alex S.
Walton
,
Reshma R.
Rao
Diamond Proposal Number(s):
[42239, 41758, 39622, 37550, 42151]
Open Access
Abstract: Nickel-based cathodes are widely used in alkaline water electrolysis, yet the nature and stability of the active surface under operating conditions remains unclear. In particular, the role of metal/oxo–hydroxo interfacial structures in governing hydrogen evolution activity is not well understood. Here, we employ a multimodal, depth-sensitive approach combining operando Ni L-edge X-ray absorption spectroscopy, depth-sensitive X-ray absorption measurements in total electron yield and Auger electron yield modes, X-ray photoelectron spectroscopy, isotopically labeled nano secondary ion mass spectrometry, and online electrochemical mass spectrometry to directly track the evolution of Ni/NiOxHy interfaces during the hydrogen evolution reaction. Using well-defined sputtered Ni thin films as a model system, we show that progressive reduction of near-surface oxide/hydroxide species is accompanied by a gradual loss of hydrogen evolution activity. Depth-resolved measurements reveal a predominantly metallic outermost surface under cathodic bias, while NiOxHy forms on the surface upon relaxation to open-circuit conditions. Importantly, mild anodic pre-conditioning regenerates subsurface NiOxHy species, resulting in a sustained increase in hydrogen evolution activity upon subsequent cathodic polarization. These results establish the crucial role of metal/oxo–hydroxo interfaces as active phases for hydrogen evolution and provide a framework for engineering robust, Earth-abundant HER cathodes capable of operating under dynamic, real-world electrolysis conditions.
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Aug 2026
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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Jad
Jaafar
,
Ye
Fan
,
Maryam
Kazemzadeh-Atoufi
,
Ryo
Mizuta
,
Jinfeng
Yang
,
Jack E. N.
Swallow
,
Elizabeth
Jones
,
Matthijs A.
Van Spronsen
,
Georg
Held
,
Robert S
Weatherup
,
Peter
Voorhees
,
David J.
Wales
,
Gabor
Csanyi
,
Stephan
Hofmann
Diamond Proposal Number(s):
[25633]
Open Access
Abstract: The commercialization of emerging materials is hindered by the empirical nature of process development, with the underpinning solid-state reaction kinetics remaining elusive due to their inherent multistep and multiscale character and the vast configurational and parameter space. We combine high-throughput operando scanning electron microscopy (OSEM) with extended classical continuum and phase-field simulations and atomistic machine-learned interatomic potential (MLIP) surrogate models to demonstrate effective foundational reaction exploration, using thermal oxidation of chemical-vapor-deposited monolayer WS2 across a temperature range of 450–680 °C as our benchmark reaction. OSEM provides statistically relevant reaction data sets of spatiotemporal basal plane nucleation kinetics and propagation of tens of thousands of individual 1D reaction facets, revealing time-dependent rates. By extending Avrami theory and employing a calibrated phase-field model, we extract an apparent nucleation barrier of 1.1 eV and show that the complex rate behavior arises from mixed reaction–diffusion control. Atomistic reaction exploration via MLIPs guided by these experimental data reveals that oxidative reaction chains leading to W volatilization and etch pit formation are driven not by the most common sulfur or substitutional oxygen point defects but by more complex defects such as W vacancies. MLIP diffusion barrier screening identifies the role of chemisorbed hydroxyl species for this reaction scenario, while systematic screening of 1D edge configurations and their terminations uncovers the structural origins of the pronounced in-plane reaction anisotropies. We discuss the potential of our synergistic approach to effectively bring experimental and computational approaches closer together and accelerate critically required process discovery for advanced materials.
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May 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
B18-Core EXAFS
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Ainara
Aguadero
,
Federico
Baiutti
,
Monica
Burriel
,
Markus
Kubicek
,
Alexander Karl
Opitz
,
Juergen
Fleig
,
David
Munoz-Rojas
,
Christophe
Vallée
,
Marceline
Bonvalot
,
Alexia
Popescu
,
Nicola H
Perry
,
Francesco M.
Chiabrera
,
Álex
Morata
,
Juan Carlos
Gonzalez-Rosillo
,
Alexander
Stangl
,
Ramon
Escobar-Galindo
,
Mattias
Krause
,
Sivakkumaran
Sukumaran
,
Sarah
Fearn
,
Richard J.
Chater
,
Stephen J.
Skinner
,
John
Kilner
,
Sören
Möller
,
Martin
Finsterbusch
,
Manoj Kumar
Ghosalya
,
Samuli
Urpelainen
,
Christoph
Baeumer
,
Santosh
Kumar
,
Veronica
Celorrio
,
Diego
Gianolio
,
David C.
Grinter
,
Pilar
Ferrer-Escorihuela
,
Georg
Held
,
Jordi
Cabana
,
Sandrine
Lyonnard
,
Dorthe
Bomholdt Ravnsbaek
,
M. Rosa
Palacin
,
Montserrat
Casas-Cabanas
,
Julie
Villanova
,
Aline
Léon
,
Qiucheng
Xu
,
Jakub
Drnec
,
Brian
Seger
,
David R
Diercks
,
Nejc
Hodnik
,
Lluís
Yedra
,
Sonia
Estrade
,
Francesca
Peiró
,
Neus
Domingo
,
Maciej O
Liedke
,
Enric
Menéndez
,
David J.
Keeble
,
Jakub
Čížek
,
Ralf F.
Ziesche
,
Oriol
Sans Planell
,
Nikolay
Kardjilov
,
Ingo
Manke
,
Daniele
Pergolesi
,
Jochen
Stahn
Open Access
Abstract: A strong societal and political drive is motivating the development and optimization of novel
energy
conversion and storage systems for decarbonization. The successful implementation of solid
state devices such as fuel cells and secondary batteries depends, however, on achieving
ambitious targets in terms of performance, reliability and cost competitiveness. Research and
technology are addressing these needs through a holistic approach including exploration of new
materials and nanoarchitectures, as well as system engineering. These significant efforts require
the support of appropriate characterization tools capable of assessing nanometer-scale
phenomena such as concentration profiles of ionic and electronic charges, local chemical
compositions and their evolution over time across interfaces.
This roadmap provides an overview of selected advanced characterization techniques for
energy materials and devices. Specific focus is put on in situ/operando methods for probing
electrochemical phenomena in real-time under realistic working conditions. Experts in the field
provide an extensive review of the current state of the art in 2025 and the current and future
challenges for the characterization of local chemistry and kinetics in the bulk of the material, in
nanoarchitectures (e.g. thin films) and at the interfaces (e.g. grain boundaries, phase contacts,
solid/liquid and solid/gas interfaces) . The aim is to provide a detailed guide to the techniques,
describing opportunities and bottlenecks for their practical deployment and examples of
successful
applications.
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May 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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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.
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Apr 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B18-Core EXAFS
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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.
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Apr 2026
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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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.
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Mar 2026
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
E01-JEM ARM 200CF
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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.
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Mar 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B18-Core EXAFS
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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.
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Feb 2026
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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.
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Feb 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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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.
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Dec 2025
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