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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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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B18-Core EXAFS
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Yinghao
Xu
,
Yi-Hsuan
Wu
,
Paula M.
Abdala
,
Connor
Sherwin
,
Veronica
Celorrio
,
Diana
Piankova
,
Payal
Chaudhary
,
Vitaly
Alexandrov
,
Agnieszka
Kierzkowska
,
Denis A.
Kuznetsov
,
Christoph R.
Müller
Diamond Proposal Number(s):
[36625]
Open Access
Abstract: Iridium-based oxides are among the most promising catalysts for the acidic oxygen evolution reaction (OER) owing to their high catalytic activity and stability. Substituting iridium with earth-abundant elements could lower costs and potentially boost its intrinsic activity even further; however, no unambiguous structure–activity relationships describing the physical origins of the effect of the substituent for this class of electrocatalysts have been established. In this work, we utilized a series of IrOx(:M) nanoparticle catalysts to correlate their in situ structural changes with intrinsic OER activity. We observe that IrOx(:M) with M = W and In feature a significantly higher Ir-mass-normalized OER activity than IrOx, however the activity enhancements have a different origin. While the increased activity of IrOx[thin space (1/6-em)]:[thin space (1/6-em)]In stems from a higher number of electrochemically active iridium centers (due to the leaching of indium), IrOx[thin space (1/6-em)]:[thin space (1/6-em)]W features a higher intrinsic OER activity compared to IrOx, due to electronic effects of W on neighboring Ir/O sites. Furthermore, operando electrochemical mass spectrometry experiments and density functional theory (DFT) calculations revealed that the enhanced OER activity of IrOx(:M) does not originate from a promotion of the lattice oxygen coupling mechanism, but is instead associated with a facilitated conventional adsorbate evolution mechanism.
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Oct 2025
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B18-Core EXAFS
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Charlie A. F.
Nason
,
Ajay Piriya
Vijaya Kumar Saroja
,
Wanjun
Ren
,
Yingkangzi
Mei
,
Asma
Sarguroh
,
Yupei
Han
,
Yi
Lu
,
Jamie A.
Gould
,
Tim I.
Hyde
,
Veronica
Celorrio
,
Gopinathan
Sankar
,
Yang
Xu
Diamond Proposal Number(s):
[39009, 39790]
Open Access
Abstract: The ultimate goal of potassium-ion batteries (KIBs) is to become a serious competitor to lithium-ion batteries (LIBs). Achieving this requires the development of high energy density negative electrode materials, with transition metal oxides emerging as the most promising candidates. However, despite their high theoretical capacities, most transition metal oxides still struggle to achieve high performance, often necessitating substantial nanostructuring. Ion-exchange presents a facile and effective process for enhancing material properties, yet the demonstration of the exchanged ions undergoing redox activity has not been previously reported for KIBs. Herein, this work reports Ni0.25K0.5TiNbO5, synthesized through the ion-exchange between K+ and Ni2+, as a novel negative electrode material for KIBs. The ion-exchanged material achieves a specific capacity of 304 mAh g−1 in the first cycle and 162 mAh g−1 after 10 cycles, corresponding to a 240% and 156% increase compared to the pristine, unexchanged KTiNbO5 at the same cycle numbers. The structure–performance relationship was investigated in detail, shedding light on the previously unknown relationships between the level of hydration, degree of exchange and the performance of ion-exchanged materials. Furthermore, the exchanged Ni was demonstrated to be reversibly redox active, contributing to the observed capacity and representing a first for ion-exchanged materials in the KIB literature.
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Sep 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[25434]
Open Access
Abstract: A new solid solution series based on substitution of Cr into LiNiVO4, with the stoichiometric formula Li2+xNi2-2xCrxV2O8 (0 ≤ x ≤ 1), is reported here for the first time. The materials crystallise in the Fd3-m space group as inverse spinels, with (at ambient temperatures) vanadium on the tetrahedral site and Li, Cr and/or Ni filling the octahedral interstices. High temperature neutron diffraction data are used to identify a continuous three-dimensional Li+-ion conduction pathway along 16c-8a-16c sites, with bulk activation energies ranging from 0.17 eV for powdered specimens to 0.53 eV for samples sintered at 550 - 650 °C. Lithium diffusion coefficients at 300 K were calculated from muon spectroscopy data to be in the region of 2 x 10-12 cm2 s-1. Preliminary electrochemical data show significant capacity loss after first discharge when employed as positive electrodes, as is common for similar inverse spinels, but show significant promise for anode applications with ca. 110 mAh g-1 in reversible specific capacity remaining after 50 cycles at an average operating potential of ~ 0.6 V.
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Sep 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[27861]
Open Access
Abstract: Zinc–air redox flow batteries have high potential to penetrate the stationary energy storage market, due to the abundancy, and low cost of active species – oxygen and zinc. However, their technological fruition is limited by the development of reversible O2 electrodes operating at potentials between 0.6 VRHE to 1.7 VRHE, under which no catalyst material has been shown to be stable over long durations. Despite heavy research on the topic of reversible O2 catalysis, little is known about the parameters controlling the stability of the bifunctional catalyst. Several research accounts assess the activity of reversible O2 catalysts, but only a small portion cover degradation mechanism over such a large potential window. In this perspective, we summarize our current understanding of material challenges for Zn–air batteries, reversible O2 catalyst integration strategies, and electrochemical behaviour, with a particular focus on catalyst stability. Nickel cobalt oxide (NiCo2O4), a promising yet understudied system, is used as an example material for investigations at potentials of both the O2 reduction (ORR) and evolution (OER) reactions. We also report original data employing ex situ X-ray diffraction, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy, as well as electrochemical measurements to study the activity of NiCo2O4. Furthermore, electrochemical accelerated stress tests are coupled with post-mortem transmission electron microscopy, inductively coupled plasma, and X-ray photoelectron spectroscopy to study the dissolution, compositional changes and amorphization of the top surface 5 nm of the catalyst surface. In situ X-ray absorption spectroscopy revealed irreversible oxidation of Co centres in NiCo2O4 during OER, which explains the reduction in activity of the ORR after the catalyst was exposed to anodic OER potentials. This methodology provides a broader method to screen reversible O2 catalyst stability and enables us to summarize future strategies to improve the activity and stability of reversible O2 catalysts and electrodes.
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Sep 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[40853]
Abstract: Single metal atom catalysts (SACs) are receiving widespread attention in electrochemical energy conversion reactions due to the rational use of metal resources and maximum atom utilization efficiency. The role of the support in stabilizing the single atoms is crucial for their catalytic stability. Carbon nitride (CN) is an excellent support for SACs but its low electrical conductivity is not appropriate for electrochemical applications. Here, we report an engineered composite material based on multiwall carbon nanotubes (MWCNTs) and single nickel atoms stabilized on CN (Ni–CN) as efficient and robust electrocatalyst for the oxygen evolution reaction (OER). Composites with different mass Ni–CN:MWCNT ratios have been prepared to optimize the contribution of both materials, and characterized by X-ray diffraction, transmission electron microscopy, X-ray absorption, and X-ray photoemission spectroscopy. Results confirmed the self-assembly of both materials and the condensation of the triazine-based structure of CN into heptazine-based onto the MWCNTs’ surface during the synthesis, as well as the presence of single Ni atoms in the composites. The co-presence of NiO nanoparticles was detected for the samples with the highest Ni content. The ratio of NiO nanoparticles to single-atom Ni centers was governed by the Ni–CN:MWCNT ratio employed during synthesis. Electrochemical characterization showed a synergistic effect between Ni–CN and MWCNTs that boosted the OER activity of the composites respect to the individual components. The 1:2 ratio turned out to be the optimal one for the composite preparation, maximizing the combined effects of the catalytic activity of the Ni centers and the electrical conductivity of MWCNTs. The mass activity obtained by this composite was 30 times higher than that of the Ni–CN starting material, attributable to its superior electrical conductivity and improved accessibility of Ni active sites. This study underscores the potential of composite materials to advance SACs toward large-scale application.
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Aug 2025
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B18-Core EXAFS
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Roser
Fernández‐climent
,
Daniele
Giusi
,
Matteo
Miceli
,
Camilo A.
Mesa
,
Ana
Gutiérrez-Blanco
,
Junnan
Li
,
Jesús
Redondo
,
Frederik
Schiller
,
Sara
Barja
,
Veronica
Celorrio
,
Nikolay
Kornienko
,
Claudio
Ampelli
,
Sixto
Gimenez
Diamond Proposal Number(s):
[36993]
Open Access
Abstract: Precise control over the dynamic transformations that electrocatalysts undergo under operating conditions offers a powerful strategy for tailoring catalytic selectivity. Herein, the electrochemical modification of Cu2−xS-derived catalysts to generate selective active sites for the electroreduction of CO2 to formate is investigated. Through a combination of in situ and ex situ characterization techniques, it is demonstrated that electrochemical cycling induces sulfur leaching, resulting in the formation of reduced, amorphous copper structures that exhibit enhanced selectivity toward formate production. Compared to the pristine material, the electrochemically modified catalyst achieves a twofold improvement in Faradaic efficiency, reaching values as high as 75% for CO2-to-formate conversion. These findings not only establish a cost-effective and scalable platform for catalyst fabrication and activation, but also open new avenues for advancing sustainable CO2 conversion technologies toward industrial implementation.
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Aug 2025
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
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Lucy
Costley-Wood
,
Nicolás
Flores-González
,
Claire
Wilson
,
Paul
Thompson
,
Sarah
Day
,
Veronica
Celorrio
,
Donato
Decarolis
,
Ruby
Morris
,
Manfred E.
Schuster
,
Huw
Marchbank
,
Timothy I.
Hyde
,
Amy
Kolpin
,
Dave
Thompsett
,
Emma K.
Gibson
Diamond Proposal Number(s):
[29993, 29695, 19850]
Open Access
Abstract: The impact of rare-earth (RE) doping in ceria-zirconia─critical for enhancing thermal stability and optimizing redox properties─on surface palladium (Pd) behavior has been investigated. RE doping was found to weaken metal–support interactions, leading to increased Pd mobility, with notable effects on oxygen storage capacity and light-off performance under model exhaust conditions. The mobility and redox characteristics of Pd were assessed through in situ thermal experiments using X-ray absorption spectroscopy at the Pd K-edge and synchrotron powder diffraction. Complementary Ce K-edge EXAFS and Rietveld refinements confirmed the structure and composition of the doped ceria-zirconia material. Deactivation studies and lifetime prediction are essential for commercial catalysts, particularly for three-way catalysts (TWCs) designed for decade-long operation. To probe long-term stability, in situ thermal treatments were conducted to induce separation of the metastable ceria–zirconia solid solution. These accelerated thermal aging treatments were then compared with a prolonged, seven week aging protocol, and regular in situ synchrotron PXRD measurements provided insights into the phase separation process. The influence of thermal aging on metal–support interactions was further assessed through catalytic performance testing.
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Aug 2025
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B18-Core EXAFS
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Suman
Pradhan
,
Jun
Hu
,
Peng
Ren
,
Yuman
Qin
,
Noopur
Jain
,
Susanna
Monti
,
Giovanni
Barcaro
,
Aleksander
Jaworski
,
Xingchao
Dai
,
Jabor
Rabeah
,
Joaquin
Silvestre-Albero
,
Veronica
Celorrio
,
Anna
Rokicińska
,
Piotr
Kuśtrowski
,
Sandra
Van Aert
,
Sara
Bals
,
Shoubhik
Das
Diamond Proposal Number(s):
[32609]
Abstract: Regioselective C–H bond functionalization is pivotal in modern scientific exploration, offering solutions for achieving novel synthetic methodologies and pharmaceutical development. In this aspect, achieving exceptional regioselective functionalization, like para-selective products in electron-poor aromatics, diverges from traditional methods. Leveraging the advantages of atomically dispersed photocatalysts, we designed a robust photocatalyst for an unconventional regioselective aromatic C–H bond functionalization. This innovation enabled para-selective trifluoromethylations of electron-deficient meta-directing aromatics (-NO2, -CF3, -CN, etc.), which is entirely orthogonal to the traditional approaches. Mechanistic experiments and DFT analysis confirmed the interaction between Cu-atom and the aromatic substrate, alongside the photocatalyst's molecular arrangement, driving selective exposure of the para-selective functionalization. This strategic approach elucidated pathways for precise molecular transformations, advancing the frontier of regioselective C–H bond functionalization by using atomically dispersed photocatalysts in organic synthesis.
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Jun 2025
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