B18-Core EXAFS
E01-JEM ARM 200CF
I09-Surface and Interface Structural Analysis
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Thomas J.
Liddy
,
Benjamin J.
Young
,
Emerson C.
Kohlrausch
,
Andreas
Weilhard
,
Gazi N.
Aliev
,
Yifan
Chen
,
Manfred E.
Schuster
,
Mohsen
Danaie
,
Luke L.
Keenan
,
Donato
Decarolis
,
Diego
Gianolio
,
Siqi
Wang
,
Mingming
Zhu
,
Graham J.
Hutchings
,
David M.
Grant
,
Wolfgang
Theis
,
Tien-Lin
Lee
,
David A.
Duncan
,
Alberto
Roldan
,
Andrei N.
Khlobystov
,
Jesum
Alves Fernandes
Diamond Proposal Number(s):
[38764]
Open Access
Abstract: Ammonia is an attractive hydrogen carrier, yet its practical use is limited by the need for efficient catalytic decomposition. We demonstrate that in-situ N-doping of Ru nanoparticles and graphitized carbon nanofiber supports during reaction produces a sharp increase in hydrogen production during the first 40 h, followed by stable activity. Spectroscopic and microscopic analyses, together with density functional theory simulations, reveal that Ru nitridation is rapid and support-independent, resulting in a mechanistic shift from the traditional Langmuir–Hinshelwood to a Mars–van Krevelen pathway, further confirmed by isotopic labelling experiments. In contrast, the progressive nitridation of the carbon support, observed via X-ray photoelectron spectroscopy, modulates the electronic environment of Ru and functions as a dynamic nitrogen reservoir that enables reversible N atoms exchange with the Ru particles, facilitating N desorption from the Ru surface and thereby governing the catalytic activity enhancement. These new findings provide new mechanistic insight into ammonia decomposition and establish progressive nitrogen doping of carbon supports as a strategy for designing efficient metal-based catalysts for hydrogen production.
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Dec 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[32381]
Abstract: This study aimed at determining Ni and Co leaching kinetics from a New Caledonian laterite in an acidic medium (H2SO4 pH 1.5) and in a reductive environment (addition of SO32− or Fe(II)) at 46 °C. The mineralogical study revealed that Co was mainly carried by Mn oxyhydroxides in the limonite sample. Conversely, Ni was hosted by both Fe and Mn oxyhydroxides. In the presence of a reductive reagent, Mn oxyhydroxides dissolved rapidly compared to goethite, the main Fe oxyhydroxide in the sample. Co, Mn and Ni reductive leaching yields reached 79 %, 83 % and 9 % respectively after 2 days. Based on these results, a Mn oxides concentrate was produced in order to efficiently leach Co while limiting Fe oxyhydroxide dissolution. This concentrate resulted from a combination of particle size and gravity separation steps. The volume/mass of sample was drastically decreased since the mass of the final sample was only 3.3 % of the initial one. Co content increased from 0.16 wt% in the limonite to 2.3 wt% in the concentrate, representing an enrichment factor of 13.8 and recovery yield of 60 %. Co, Mn and Ni leaching yields reached 87 %, 95 % and 80 % respectively in the Mn oxides concentrate leaching experiment. The difference in Ni behaviour was consistent with the mineralogical composition: Ni was mainly carried by the goethite in the laterite, while it was hosted mainly by the Mn oxyhydroxides in the Mn oxides concentrate. This study gives a proof of concept for the development a robust pre-concentration process to recover Co.
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Nov 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[38597]
Open Access
Abstract: Extra-large-pore Ge-containing GTM chiral zeolite catalysts have recently proved useful asymmetric catalysts, with chirality emerging from their chiral confined nanospace. However, so far these exceptional materials have suffered from low framework stability in the presence of water and moderate catalytic enantioselectivity in the ring-opening of chiral trans-stilbene oxide with 1-butanol used as a test reaction. Here, we report that these chiral zeolite catalysts can be easily stabilized upon exposure of the calcined material to 1-butanol, providing stability against water and, most importantly, prompting a preactivation of the chiral active sites that boosts their enantioselective properties, reaching unprecedented enantiomeric excesses up to 88% where one enantiomer reacts 16 times more than the other. A range of physicochemical studies, including in situ Fourier transform infrared (FTIR) and X-ray absorption spectroscopy, indicates that framework Ge sites increase their coordination environment upon interaction with 1-butanol molecules, which after a thermal treatment above 100 °C remain irreversibly bound to Ge as a consequence of a condensation and dehydration reaction, providing a route to easily functionalize these materials. These preactivated GTM asymmetric catalysts act similarly to enzymes by controlling the confinement of the chiral reactants in particular orientations through coordination with Ge and development of H-bonds with nearby hydroxyl groups, thus attaining enantioselective catalytic activities close to those reached by enzymatic systems but with the crucial advantage associated with heterogeneous catalysts and, notably, the possibility of preparing both enantiomeric versions of the catalyst by using an easily accessible alkaloid.
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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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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B18-Core EXAFS
I14-Hard X-ray Nanoprobe
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Lotfi
Boudjema
,
Anil Kumar
Dahiya
,
Ivan
Da Silva
,
Diego
Gianolio
,
Izuchika
Nduka
,
Manfred Erwin
Schuster
,
Gea T.
Van De Kerkhof
,
Paulina
Kalinowska
,
Emilio
Borrego-Marin
,
Jorge A. R.
Navarro
,
Valentina
Colombo
,
June
Mccorquodale
,
David C.
Grinter
,
Pilar
Ferrer
,
Georg
Held
,
C. Richard A.
Catlow
,
Rosa
Arrigo
Diamond Proposal Number(s):
[28630]
Open Access
Abstract: We investigate the rapid microwave-assisted solvothermal synthesis of a Cu-MOF (Metal-Organic Framework) with open metal sites, with a focus on understanding its CO2 capture properties in relation to phase purity and stability. A combined experimental and theoretical approach is used to identify the MOF structural features involved in the adsorption process. Specifically, Cu(I) defects are found playing an important role in the CO2 adsorption process, with the Cu-1 sample, synthesized using an optimized ligand/Cu precursor ratio for highest phase purity, exhibiting more abundant Cu(I) defects as well as highest adsorption capacity. Grand Canonical Monte Carlo simulations show that the Cu(I) sites exhibit a greater affinity for CO2 adsorption compared to the Cu(II) sites. In situ spectroscopic soft and hard X-ray absorption fine structure spectroscopy confirm the conversion of Cu(I) to Cu(II) upon CO2 chemisorption, with this conversion being more pronounced in the core of the particles. The simulations are used to estimate the fraction of Cu(I) defects and Cu(II) sites present within the Cu-1 MOF and to validate the experimental isotherm. Overall, this study provides insights into the CO2 capture properties of GIF-KUC Cu-MOFs and highlights the importance of phase purity for achieving high adsorption performance.
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Jun 2025
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B18-Core EXAFS
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Chunguang
Kuai
,
Liping
Liu
,
Anyang
Hu
,
Yan
Zhang
,
Yuxin
Zhang
,
Dawei
Xia
,
Dennis
Nordlund
,
Dimosthenis
Sokaras
,
Donato
Decarolis
,
Diego
Gianolio
,
Hongliang
Xin
,
Luxi
Li
,
Feng
Lin
Diamond Proposal Number(s):
[38784]
Abstract: The oxygen evolution reaction is a key process in many energy technologies, but improving its efficiency remains challenging due to the energy scaling relationships that limit the reaction kinetics on conventional single-active-site solid catalysts. Here we report a cooperative solid–molecular mechanism for oxygen evolution on NiFe-based hydroxide electrocatalysts. By identifying the critical interfacial species and understanding their dynamics, we find that molecular FeO42− species, derived from the dissolution of Fe from the solid catalyst, act as molecular co-catalysts that participate in the critical O–O bond-formation step along with solid sites. This synergistic mechanism, involving both solid and molecular active species, circumvents the typical scaling limitations observed for solid catalysts alone. Our findings reveal an unconventional solid–molecular mechanism that governs electrocatalysis at the solid–liquid interface and suggest a strategy for transcending scaling constraints through cooperative multi-site catalysis.
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May 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B18-Core EXAFS
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Diamond Proposal Number(s):
[32514]
Open Access
Abstract: Fe/N/C based catalysts are the best positioned ones to replace the state-of-the-art Pt-based catalysts for the oxygen reduction reaction (ORR) in Proton Exchange Membrane Fuel Cells (PEMFCs). Here, a Fe/N/C catalyst characterized by a high N/C ratio, has been synthesized from the pyrolysis of a N-rich imine-based polymer. In acidic electrolyte (0.1 M HClO4). The catalyst demonstrates notable ORR activity with Eonset and E1/2 values of 1.09 and 0.77 V vs. RHE, respectively. Furthermore, the catalyst’s performance has been assessed in a single cell PEMFC setup. The optimization of the membrane electrode assembly (MEA) with the Fe/N/C catalyst entails examining various ionomer to catalyst ratios (I/C) as well as two coating methods: spray coating and drop casting. The optimized MEA achieved a cell performance of 725 mA cm-2 at 0.3 V and a power density close to 220 mW cm-2. In order to understand the factors influencing PEMFC polarisation curves, electrochemical impedance spectroscopy (EIS) was performed under potentiostatic conditions. The effect of operational parameters, such as ionomer to catalyst ratios (I/C) and the use of either O2 or air at the anode feed, has been investigated. EIS spectra allow the calculation of the distribution of relaxation times (DRT), providing insights into the rate and resistance of the ORR process occurring at the MEA. Notably, the cathode with an I/C=2, prepared by drop casting, exhibited superior performance attributed to reduced ORR resistances. The current density and power density reached with the 25 cm2 MEA are comparable to those obtained with the 5 cm2 MEA using O2 as cathode reactant.
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Apr 2025
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B18-Core EXAFS
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Santhosh K.
Matam
,
Preetam K.
Sharma
,
Eileen H.
Yu
,
Charalampos
Drivas
,
Mohammad D.
Khan
,
Martin
Wilding
,
Nitya
Ramanan
,
Diego
Gianolio
,
Mark A.
Isaacs
,
Shaoliang
Guan
,
Philip R.
Davies
,
C. Richard A.
Catlow
Diamond Proposal Number(s):
[29271]
Open Access
Abstract: We present a novel operando X-ray absorption spectroscopic (XAS) flow cell, consisting of a gas chamber for CO2 and a liquid chamber for the electrolyte, to monitor electrochemical CO2 reduction (eCO2R) over a gas diffusion electrode (GDE). The feasibility of the flow cell is demonstrated by collecting XAS data (during eCO2R over Cu-GDE) in a transmission mode at the Cu K-edge. The dynamic behaviour of copper during eCO2R is captured by XAS which is complemented by quasi in situ Raman and X-ray photoelectron spectroscopy (XPS). The linear combination analyses (LCA) of X-ray absorption near edge structure (XANES) indicate that copper oxides are the only species present during the first 20 min of eCO2R, corroborated by complementary Raman and XPS. Significantly, the complementary spectroscopic data suggests that the copper composition in the bulk and on the surface Cu-GDE evolve differently at and above 30 min of eCO2R. LCA indicates that at 60 min, 77% of copper occurs as metallic Cu and the remainder 23% in Cu (II) oxidation state, which is not evident from XPS that shows 100% of copper in < 2+ oxidation state. Thus, the Cu (II) is probably in the bulk of Cu-GDE, as also evident from Raman. The ethylene formation correlates very well with the occurrence of copper oxides and hydroxide species in Cu-GDE. The results not only demonstrate the applicability and versatility of the operando XAS GDE flow cell, but also illustrate the unique advantages of combining XAS with complementary Raman and XPS that enables the monitoring of the catalyst structural evolution from the bulk to surface and surface adsorbed species.
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Dec 2024
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Abstract: The instrumentation and experimental setups needed to investigate catalysts by X-ray absorption spectroscopy (XAS) under in situ and operando conditions are briefly described. The relevance of the simultaneous collection of XAS data while monitoring the activity and selectivity of the catalyst (operando setups) is stressed and the compromises that are necessary to construct an operando cell are discussed. The same approach is used for cells that allow additional simultaneous data collection (X-ray powder diffraction, small-angle X-ray scattering, infrared, Raman or UV–visible). The role of time-resolved and space-resolved experiments is discussed, together with the need for sophisticated software that is able to handle a huge amount of XAS spectra coupled with other independent data collections.
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Aug 2024
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B18-Core EXAFS
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Diamond Proposal Number(s):
[28630]
Open Access
Abstract: In this study, nickel nanoparticles were successfully synthesized using two methods: the hot-injection method and a room temperature colloidal synthesis using dioctyl tartrate as a capping agent. Each approach yielded Ni nanoparticles with unique morphological and electronic properties. The distinct characteristics of these Ni nanoparticles make them promising candidates for unravelling structure/activity relationships, a crucial aspect in developing catalysts with enhanced selectivity. Ni nanoparticles synthesized via these methods were supported on silica and activated charcoal, with variations in Ni loadings. We explored the impact of nanostructural characteristic of the Ni nanoparticles as well as support effects on the selective hydrogenation of furfural. Using temperature programmed reduction, advanced X-ray absorption spectroscopy, and atom-resolved electron microscopy techniques, we established comprehensive structure-function relationships. We demonstrate that via dioctyl tartrate route, foam-like Ni nanostructures are obtained, yielding higher selectivity towards selective hydrogenation than commercial Ni/Al2O3 and suppression of acid-base catalysed acetalization and etherification. Furthermore, conversions similar to commercial Ni/Al2O3 are achieved using a lower Ni loading. These insights provide valuable guidance for the design of enhanced materials, contributing to the optimization of catalyst performance in selective hydrogenation processes. This research marks a significant step toward the development of more efficient and sustainable catalytic processes.
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Jun 2024
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