B18-Core EXAFS
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Diamond Proposal Number(s):
[34275, 39622]
Abstract: Layered manganese dioxide (MnO2) stands out for its ability to act as a host for cation intercalation, which can significantly enhance its performance for the oxygen evolution reaction (OER). However, the role of intercalated cations in enhancing this reaction remains unknown. Herein, by systematically investigating various cation-intercalated (K+, Fe3+, Co2+, Ni2+, and Cu2+) layered manganese oxides, we demonstrate that the intercalated transition metal cations serve as the primary active sites. We find that the oxidation state of cations within the MnO2 layers is determined by their relative Lewis acidity compared to the host Mn. This correlation between OER activity and the resulting electronic redistribution suggests that relative Lewis acidity of intercalated cations can determine the electronic redistribution between intercalated cations and MnO2 layers, which in turn regulates the oxidation of both components. Therefore, we propose that relative Lewis acidity serves as a descriptor for OER activity. This work highlights the critical role of host-imposed electronic limits, establishing a rational design principle for future layered material-confined systems.
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Jul 2026
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B18-Core EXAFS
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Diamond Proposal Number(s):
[19850]
Open Access
Abstract: Integrating urea electrolysis into wastewater treatment systems represents a promising strategy to couple hydrogen production with environmental remediation. Nickel-based materials are among the most efficient non-precious catalysts for the urea oxidation reaction under alkaline conditions, yet Ni scarcity and its potential toxicity call for more sustainable alternatives. After demonstrating that Ni hydroxide recovered from wastewater is a good urea oxidation reaction catalyst, in this work, we report a fundamental and systematic study about urea oxidation reaction catalysts based on manganese-doped nickel hydroxide obtained through a synthesis route that mimics Ni recovery from wastewater to enhance the urea oxidation reaction performance. Thus, it offers both catalytic performance and circular-material benefits. A comprehensive characterization of the Ni(OH)2-based materials by experimental techniques, such as X-ray diffraction, scanning electron microscopy, X-ray absorption, and X-ray photoemission spectroscopy, combined with DFT theoretical calculations has revealed that Mn incorporation modifies the hydroxide structure, introduces ions in the +3 oxidation state, and promotes the formation of catalytically active NiOOH species. Mn dopants induce a favorable electronic effect through an indirect participation in the urea oxidation reaction mechanism involving oxidation state variation but not direct chemical bond formation. The reaction intermediates are in part different from those reported in previous literature. At a given potential, Mn doping enhances the overall urea oxidation rate, resulting in increased hydrogen evolution at the cathode. These findings point to a novel mechanistic understanding of the Mn-dopant role through its ability for an easier change to higher oxidation states than Ni ions, which reflects in a more favorable energetics of NiOOH formation and an improved urea oxidation reaction catalysis based on circular earth-abundant elements.
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Jun 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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B18-Core EXAFS
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[21659, 28356]
Open Access
Abstract: Understanding the interplay between redox behavior and structural stability is crucial for the development of transition metal oxides in electrocatalysis. In this work, we use both X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) to investigate the electrochemical response of Mn-based perovskite oxides (La1–xCaxMnO3) under oxygen reduction reaction (ORR) conditions. This dual approach enables tracking of changes in both the oxidation state and local coordination environment. Mn Kβ XES data show that oxidation-state changes are reversible, despite a shift in transition potentials across a range of compositions, including CaMnO3. In contrast, Mn K-edge EXAFS analyses reveal that while LaMnO3 retains structural integrity, CaMnO3 undergoes irreversible structural changes at low potentials, associated with the collapse of the perovskite framework. Intermediate compositions show partially reversible structural behavior. This decoupling of redox reversibility and structural instability, a picture only accessible through the use of XAS and XES, provides critical insight into the complex behavior of these materials under operational conditions. Additionally, our analysis shows that Mn(II) formation is only detected in CaMnO3 at potentials more negative than 0.4 V (vs RHE). The ORR onset is associated with Mn(IV) reduction, while peroxide formation correlates with an increased Mn(III)/Mn(IV) ratio, supporting a 2e– + 2e– reduction pathway. This study demonstrates the power of XAS and XES analyses to disentangle electronic and structural dynamics, providing a more complete understanding of activity–stability relationships in perovskite electrocatalysts.
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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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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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B18-Core EXAFS
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Diamond Proposal Number(s):
[38116]
Open Access
Abstract: Increasing use of lithium-ion batteries (LIBs) urges for efficient recycling strategies for their components. Direct recycling methods for cathode materials, based on repairing the structure of the degraded cathode particles without destroying the bulk phase, are promising energy-saving alternatives to traditional metallurgy processes that involve several steps and use large volumes of chemicals causing secondary pollution. Herein, we report a novel and scalable method for the direct electrochemical recycling of spent lithium iron phosphate (LFP) powder in a flow cell via redox mediation. In this method, pellets of spent LFP powder (S-LFP) placed in a tank are directly reduced and relithiated by a redox mediator dissolved in a Li-containing aqueous electrolyte, pumped from an electrochemical cell stack to the relithiation tank. Redox mediators transport charge to the S-LFP pellets from the electrochemical cell, where Li4Fe(CN)6 is oxidized and Li ions are supplied from a Li4Fe(CN)6-containing counter compartment through an ion-selective membrane. The consumption of the regenerating redox mediator solution is minimal via a closed-loop electrochemical regeneration reaction. Successful S-LFP regeneration using two redox mediators, with different energy demand processes, is confirmed by structural and electrochemical characterization.
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Dec 2025
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B18-Core EXAFS
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Connor
Sherwin
,
Veronica
Celorrio
,
Alessandro
Difilippo
,
Katie
Rigg
,
Mark
Clapp
,
Armando
Ibraliu
,
Luke
Luisman
,
Thomas
Wakelin
,
Amber
Watson
,
Nikolay
Zhelev
,
Lucy
Mcleod
,
Christopher
Zalitis
,
Andrea E.
Russell
Diamond Proposal Number(s):
[35671, 10915, 30590, 33009]
Open Access
Abstract: Understanding the structural properties of iridium oxide electrocatalysts under operational conditions is critical for elucidating the structure–property relationships that enhance the catalytic activity for the oxygen evolution reaction. In this study, in situ X-ray absorption spectroscopy under realistic conditions was employed to investigate the potentiodynamic and time-resolved structural evolution of a commercial iridium oxide, alongside its fully hydrated and crystalline counterparts. Our findings reveal two distinct electrochemical regimes, a low potential plateau associated with a nonconductive Ir3+ state and a linear region where small potential variations induce reversible oxidation state and structural transformations. The structural changes were found to occur reversibly on the commercial material even after prolonged exposure to OER potentials. Notably, the hydrated IrOx exhibits extremely high OER activity, surpassing the commercial material by nearly an order of magnitude, yet it suffers from significant instability. In contrast, the crystalline IrO2 demonstrates poor activity as its catalytic performance appears to be confined to the surface. These findings highlight the critical role of hydration in modulating both activity and stability, offering valuable insights for the rational design of next generation iridium based OER catalysts.
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Dec 2025
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B18-Core EXAFS
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Open Access
Abstract: The synthesis of VOx/MgO catalysts by solution combustion synthesis was investigated using varying molar ratios of glycine to oxidant. The effect of varying the fuel amount on morphology, phase composition, surface area, crystallite size, elemental distribution, and coordination environment around V was investigated. The results showed that the morphology, surface area, and crystallite size are all dependent on the flame temperature during the combustion process, which is dependent on the amount of fuel added. Results also suggested that adding glycine in excess lowers the combustion temperature. The catalysts were tested for the ODH of n-octane. The catalyst with superior catalytic properties was the stoichiometric sample, in which equal molar ratios of the fuel and oxidizer were added. The better catalytic performance was related to the contribution of the VOx species from the magnesium vanadate phase. This is the only sample in which vanadates were detected. Catalysts synthesized under fuel-lean and fuel-rich conditions were characterized by large crystallites and the absence of detectable magnesium vanadates, using XRD.
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Nov 2025
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B18-Core EXAFS
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Rachael
Quintin-Baxendale
,
Maria
Sokolikova
,
Yemin
Tao
,
Evan
Fisher
,
Nagaraju
Goli
,
Haoyu
Bai
,
James
Murawski
,
Guangmeimei
Yang
,
Veronica
Celorrio
,
Caiwu
Liang
,
Reshma R.
Rao
,
Ifan E. L.
Stephens
,
Cecilia
Mattevi
Diamond Proposal Number(s):
[34275]
Open Access
Abstract: IrO2 is one of the most widely investigated electrocatalysts for oxygen evolution reaction in an acidic environment. Increasing the mass activity is an effective way of decreasing the loading of Ir, to ultimately reduce costs. Here, we demonstrate the crystal-phase engineering of two different potassium iridate polymorphs obtained by designing a selective solid-state synthesis of either one-dimensional K0.25IrO2 nanowires with a hollandite crystal structure or two-dimensional KIrO2 hexagonal platelets. Both structures present increased specific and mass electrocatalytic activities for the water oxidation reaction in acidic media compared to commercial rutile IrO2 of up to 40%, with the 1D nanowires outperforming the 2D platelets. XANES, extended X-ray absorption fine structure, and X-ray diffraction investigations prove the structural stability of these two different allotropes of KxIrO2 compounds upon electrocatalytic testing. These low-dimensional nanostructured 1D and 2D KxIrO2 compounds with superior mass activity to commercial IrO2 can pave the way toward the design of new electrocatalyst architectures with reduced Ir loading content for proton exchange membrane water electrolyzer (PEMWE) anodes.
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Oct 2025
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
B18-Core EXAFS
E02-JEM ARM 300CF
I11-High Resolution Powder Diffraction
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Mengqi
Duan
,
Shuai
Guo
,
Wentian
Niu
,
Hangjuan
Ren
,
Thomas
Dittrich
,
Dongpei
Ye
,
Lucy
Saunders
,
Sarah
Day
,
Veronica
Celorrio
,
Diego
Gianolio
,
Peixi
Cong
,
Robert S.
Weatherup
,
Robert
Taylor
,
Songhua
Cai
,
Yiyang
Li
,
Shik Chi Edman
Tsang
Diamond Proposal Number(s):
[35749, 35750, 35961, 37117]
Open Access
Abstract: Two-dimensional layered perovskite oxides have emerged as promising photocatalysts for solar-driven hydrogen evolution. Although doping has been widely employed to enhance photocatalytic performance, its role in modulating the electronic structure and the local chemical environment of these materials remains poorly understood. Here in this study, we investigate the codoping of Rh and La into exfoliated nanosheets of the Dion–Jacobson perovskite KCa2Nb3O10 to enhance photocatalytic hydrogen evolution reaction (HER) activity. A substantial increase in H2 evolution rate, from 12.3 to 69.0 μmol h–1, was achieved at an optimal doping level of 0.2 wt % Rh and 1.3 wt % La. Comprehensive structural and spectroscopic analyses, including synchrotron techniques and high-resolution microscopy, revealed that Rh3+ substitutes Nb5+ to introduce shallow 4d acceptor states that mediate charge separation, while La3+ substitutes Ca2+, compensates for aliovalent charge imbalance, and modulates local lattice distortions and oxygen vacancy formation. This codoping strategy enhances charge carrier lifetime and separation efficiency through a trap-mediated mechanism. The observed volcano-shaped activity trend highlights a narrow compositional window, where electronic and structural factors are optimally balanced. These findings establish a mechanistic foundation for defect engineering in layered perovskites and offer a pathway for the rational design of photocatalysts.
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Oct 2025
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