B22-Multimode InfraRed imaging And Microspectroscopy
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Leila
Abylgazina
,
Irena
Senkovska
,
Mariia
Maliuta
,
Christopher
Bachetzky
,
Marcus
Rauche
,
Kathrin
Pöschel
,
Johannes
Schmidt
,
Mark
Isaacs
,
David
Morgan
,
Michal
Otyepka
,
Eva
Otyepkova
,
Matthias
Mendt
,
Yogeshwar D.
More
,
Robin
Buschbeck
,
Andreas
Schneemann
,
Alla
Synytska
,
Andreas
Pöppl
,
Lukas M.
Eng
,
Jin-Chong
Tan
,
Eike
Brunner
,
Stefan
Kaskel
Diamond Proposal Number(s):
[30369]
Open Access
Abstract: A unique feature of flexible metal–organic frameworks (MOFs) is their ability to respond dynamically towards molecular stimuli by structural transitions, resulting in pore-opening and closing processes. One of the most intriguing modes is the “gating”, where the material transforms from the dense to the porous state. The conditions required for the solid phase structural transition are controlled by the kinetic barriers, including nucleation of the new phase commencing on the crystallite's outer surface. Thus, surface deformation may influence the nucleation, enabling deliberate tailoring of the responsivity. In the present contribution, we investigate how chemical surface treatments (surface deformation) affect the gate opening characteristics of a typical representative of gate pressure MOFs, DUT-8(Ni) ([Ni2(ndc)2(dabco)]n, ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane). A combination of various complementary advanced characterization techniques, such as NMR, nanoFTIR, terahertz, in situ XPS, in situ EPR spectroscopies, and inverse gas chromatography, are applied to unravel the changes in surface energy and mechanism of surface deformation.
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Mar 2025
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[19354]
Open Access
Abstract: Laser powder bed fusion (LPBF) of Polyamide 12 (PA12) using a near-infra-red (NIR) beam is largely unexplored; therefore, the beam-matter interaction, evolution mechanisms of the melt pool and defects remain unclear. Here, we employed a combination of in situ synchrotron X-ray imaging, ex situ materials characterisation techniques, and high-fidelity process simulations to study these behaviours during LPBF of PA12. Our results demonstrate that the NIR absorption of PA12 can be improved by 600 times through powder surface modification with C, P and Al species. In situ X-ray images reveal that the PA12 powders undergo melting, viscous merging, volume expansion, warping, solidification, and shrinkage before forming a solid track. Our results uncover the bubble evolution mechanisms during LPBF of PA12. During laser scanning, the high-energy laser beam produces organic substances/vapours which are trapped inside bubbles during viscous merging. These bubbles continue to shrink due to vapour condensation as the polymer cools under a cooling rate range of 200 - 600 K s−1. Using the collected data, we have developed a data-driven bubble shrinkage criterion to predict the bubble shrinkage coefficient using the bubble half-life, improving the build quality of LPBF polymeric parts.
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Feb 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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I20-EDE-Energy Dispersive EXAFS (EDE)
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Donato
Decarolis
,
Monik
Panchal
,
Matthew
Quesne
,
Khaled
Mohammed
,
Shaojun
Xu
,
Mark
Isaacs
,
Adam H.
Clark
,
Luke L.
Keenan
,
Takuo
Wakisaka
,
Kohei
Kusada
,
Hiroshi
Kitagawa
,
C. Richard A.
Catlow
,
Emma K.
Gibson
,
Alexandre
Goguet
,
Peter
Wells
Diamond Proposal Number(s):
[21593]
Open Access
Abstract: Unravelling kinetic oscillations, which arise spontaneously during catalysis, has been a challenge for decades but is important not only to understand these complex phenomena but also to achieve increased activity. Here we show, through temporally and spatially resolved operando analysis, that CO oxidation over Rh/Al2O3 involves a series of thermal levering events—CO oxidation, Boudouard reaction and carbon combustion—that drive oscillatory CO2 formation. This catalytic sequence relies on harnessing localized temperature episodes at the nanoparticle level as an efficient means to drive reactions in situations in which the macroscopic conditions are unfavourable for catalysis. This insight provides a new basis for coupling thermal events at the nanoscale for efficient harvesting of energy and enhanced catalyst technologies.
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Jul 2024
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Nguyen Hoai
Anh
,
Duc-Viet
Nguyen
,
Tuyen Anh
Luu
,
Pham Duc Minh
Phan
,
Huynh Phuoc
Toan
,
Pho Phuong
Ly
,
Nguyen Quang
Hung
,
Ngoc Linh
Nguyen
,
Seung Hyun
Hur
,
Pham Thi
Hue
,
Nguyen Thi Ngoc
Hue
,
Minh-Thuan
Pham
,
Thuy Dieu Thi
Ung
,
Do Danh
Bich
,
Vinh-Ai
Dao
,
Huan V.
Doan
,
Mark
Isaacs
,
Minh Chien
Nguyen
,
Woo Jong
Yu
,
Yen-Yi
Lee
,
Guo-Ping
Chang-Chien
,
Hoai-Thanh
Vuong
Diamond Proposal Number(s):
[38912]
Abstract: Increasing active sites in catalysts is of utmost importance for catalytic processes. In this regime, single-atom dispersing on graphitic carbon nitrides (g-C3N4) to produce fine chemicals, such as hydrogen peroxide (H2O2), is of current interest due to not only enhancing catalytic performance but also reducing the loading of necessary metals. Hence, we, in this research, engineered g-C3N4 by atomically dispersing aluminum (Al) or indium (In) sites to provide catalytic active centers via one-step thermal shock polymerization. The addition of Al and In sites can accelerate the catalytic efficacy owing to the Lewis acid-base interactions between these metals and oxygen (O2). Under catalytic conditions, the formation of oxygenic radicals would strongly be associated with the enhanced formation of H2O2, confirmed by in-situ electron paramagnetic resonance (EPR) spectroscopy. Furthermore, the empirical analyses from positron annihilation spectroscopy (PAS) show that In atoms would occupy the near positions of carbon vacancies (VC) to form N-VC@In-O bonds. This replacement would produce the highest formation energy based on the density functional theory (DFT) calculations, improving the stability of atom-dispersive materials. Therefore, via the combination of experimental and theoretical proofs, this study suggests the exact location of In atoms in g-C3N4 structures, which can help boost the catalytic production of H2O2.
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Apr 2024
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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Elizabeth
Jones
,
Charalampos
Drivas
,
Joshua
Gibson
,
Jack
Swallow
,
Leanne
Jones
,
Thomas
Bricknell
,
Matthijs
Van Spronsen
,
Georg
Held
,
Mark
Isaacs
,
Christopher
Parlett
,
Robert S.
Weatherup
Diamond Proposal Number(s):
[30358]
Open Access
Abstract: Environmental cells sealed with photoelectron-transparent graphene windows are promising for extending X-ray photoelectron spectroscopy (XPS) to liquid and high-pressure gas environments for in situ and operando studies. However, the reliable production of graphene windows that are sufficiently leak-tight for extended measurements remains a challenge. Here we demonstrate a PDMS/Au(100 nm)-supported transfer method that reliably produces suspended graphene on perforated silicon nitride membranes without significant contamination. A yield of ~95% is achieved based on single-layer graphene covering >98% of the holes in the silicon nitride membrane. Even higher coverages are achieved for stacked bilayer graphene, allowing wet etching (aqueous KI/I2) of the Au support to be observed in a conventional lab-based XPS system, thereby demonstrating the in situ formation of leak-tight, suspended graphene windows. Furthermore, these windows allow gas-phase measurements at close to atmospheric pressure, showing future promise for XPS under higher-pressure gas environments in conventional lab-based systems.
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Apr 2024
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B18-Core EXAFS
E02-JEM ARM 300CF
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Diamond Proposal Number(s):
[19850]
Open Access
Abstract: Alcohol oxidations are a key industrial chemical transformation, with aldehydes and ketones finding use in an array of applications. Nobel metals are known for their activity towards this chemoselective transformation, however, sustainable catalyst synthesis requires optimal utilisation of these scarce elements. Here, we report Au catalytic systems based on the deposition of isolated Au sites on different morphologies of ceria in which different surface facets of the support are exposed. Through tailoring the support morphology and from extensive catalyst characterisation, it is shown that the exposed facet is critical for controlling the formation (or not) of isolated Au sites. Both the 110 and 111 facets are capable of this feat, yielding single-atom sites for rod, octahedron, and polyhedron morphologies. In contrast, the 100 facet is not, resulting in Au nanoparticles on cubic ceria. This dictation over Au species is critical to benzyl alcohol oxidation capacity at mild conditions and in the absence of a soluble base, with only single-atom catalyst (SAC) systems demonstrating activity. Furthermore, the exposed surface facet also governs the degree of surface oxygen vacancies, which is critical to catalyst activity and arises from its control over substrate adsorption strength, as revealed through T1/T2 NMR relaxation measurements.
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Apr 2024
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Open Access
Abstract: 5-hydroxymethylfurfural represents a key chemical in the drive towards a sustainable circular economy within the chemical industry. The final step in 5-hydroxymethylfurfural production is the acid catalysed dehydration of fructose, for which supported organoacids are excellent potential catalyst candidates. Here we report a range of solid acid catalysis based on sulphonic acid grafted onto different porous silica nanosphere architectures, as confirmed by TEM, N2 porosimetry, XPS and ATR-IR. All four catalysts display enhanced active site normalised activity and productivity, relative to alternative silica supported equivalent systems in the literature, with in-pore diffusion of both substrate and product key to both performance and humin formation pathway. An increase in-pore diffusion coefficient of 5-hydroxymethylfurfural within wormlike and stellate structures results in optimal productivity. In contrast, poor diffusion within a raspberry-like morphology decreases rates of 5-hydroxymethylfurfural production and increases its consumption within humin formation.
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Oct 2023
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B18-Core EXAFS
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Diamond Proposal Number(s):
[19850]
Open Access
Abstract: The Fischer–Tropsch (FT) synthesis is traditionally associated with fossil fuel consumption, but recently this technology has emerged as a keystone that enables the conversion of captured CO2 with sustainable hydrogen to energy-dense fuels and chemicals for sectors which are challenging to be electrified. Iron-based FT catalysts are promoted with alkali and transition metals to improve reducibility, activity, and selectivity. Due to their low concentration and the metastable state under reaction conditions, the exact speciation and location of these promoters remain poorly understood. We now show that the selectivity promoters such as potassium and manganese, locked into an oxidic matrix doubling as a catalyst support, surpass conventional promoting effects. La1–xKxAl1–yMnyO3−δ (x = 0 or 0.1; y = 0, 0.2, 0.6, or 1) perovskite supports yield a 60% increase in CO conversion comparable to conventional promotion but show reduced CO2 and overall C1 selectivity. The presented approach to promotion seems to decouple the enhancement of the FT and the water–gas shift reaction. We introduce a general catalyst design principle that can be extended to other key catalytic processes relying on alkali and transition metal promotion.
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May 2023
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Open Access
Abstract: Herein, the alcoholysis of furfuryl alcohol in a series of SBA-15-pr-SO3H catalysts with different pore sizes is reported. Elemental analysis and NMR relaxation/diffusion methods show that changes in pore size have a significant effect on catalyst activity and durability. In particular, the decrease in catalyst activity after catalyst reuse is mainly due to carbonaceous deposition, whereas leaching of sulfonic acid groups is not significant. This effect is more pronounced in the largest-pore-size catalyst C3, which rapidly deactivates after one reaction cycle, whereas catalysts with a relatively medium and small average pore size (named, respectively, C2 and C1) deactivate after two reaction cycles and to a lesser extent. CHNS elemental analysis showed that C1 and C3 experience a similar amount of carbonaceous deposition, suggesting that the increased reusability of the small-pore-size catalyst can be attributed to the presence of SO3H groups mostly present on the external surface, as corroborated by results on pore clogging obtained by NMR relaxation measurements. The increased reusability of the C2 catalyst is attributed to a lower amount of humin being formed and, at the same time, reduced pore clogging, which helps to maintain accessible the internal pore space.
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May 2023
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