I19-Small Molecule Single Crystal Diffraction
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Zi
Wang
,
Alena M.
Sheveleva
,
Jiangnan
Li
,
Zhengyang
Zhou
,
Sergei
Sapchenko
,
George
Whitehead
,
Mark R.
Warren
,
David
Collison
,
Junliang
Sun
,
Martin
Schroeder
,
Eric J. L.
Mcinnes
,
Sihai
Yang
,
Floriana
Tuna
Diamond Proposal Number(s):
[31627]
Open Access
Abstract: MFM-520(Zn) confines dimers of NO2 with a high adsorption of 4.52 mmol g−1 at 1 bar at 298 K. The synthesis and the incommensurate structure of Cu-doped MFM-520(Zn) are reported. The introduction of paramagnetic Cu2+ sites allows investigation of the electronic and geometric structure of metal site by in situ electron paramagnetic resonance (EPR) spectroscopy upon adsorption of NO2. By combining continuous wave and electron-nuclear double resonance spectroscopy, an unusual reverse Berry distorted coordination geometry of the Cu2+ centers is observed. Interestingly, Cu-doped MFM-520(Zn0.95Cu0.05) shows enhanced adsorption of NO2 of 5.02 mmol g−1 at 1 bar at 298 K. Whereas MFM-520(Zn) confines adsorbed NO2 as N2O4, the presence of monomeric NO2 at low temperature suggests that doping with Cu2+ centers into the framework plays an important role in tuning the dimerization of NO2 molecules in the pore via the formation of specific host-guest interactions.
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Nov 2023
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B18-Core EXAFS
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Xuze
Guan
,
Hiroyuki
Asakura
,
Rong
Han
,
Siyuan
Xu
,
Hao-Xin
Liu
,
Lu
Chen
,
Zhangyi
Yao
,
Jay Hon Cheung
Yan
,
Tsunehiro
Tanaka
,
Yuzheng
Guo
,
Chun-Jiang
Jia
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[23759, 24450, 14239]
Open Access
Abstract: The selective catalytic oxidation of NH3 (NH3–SCO) to N2 is an important reaction for the treatment of diesel engine exhaust. Co3O4 has the highest activity among non-noble metals but suffers from N2O release. Such N2O emissions have recently been regulated due to having a 300× higher greenhouse gas effect than CO2. Here, we design CuO-supported Co3O4 as a cascade catalyst for the selective oxidation of NH3 to N2. The NH3–SCO reaction on CuO–Co3O4 follows a de-N2O pathway. Co3O4 activates gaseous oxygen to form N2O. The high redox property of the CuO–Co3O4 interface promotes the breaking of the N–O bond in N2O to form N2. The addition of CuO–Co3O4 to the Pt–Al2O3 catalyst reduces the full NH3 conversion temperature by 50 K and improves the N2 selectivity by 20%. These findings provide a promising strategy for reducing N2O emissions and will contribute to the rational design and development of non-noble metal catalysts.
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Oct 2023
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I11-High Resolution Powder Diffraction
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Open Access
Abstract: Efficient nitrogen oxides (NOx) removal from the urban atmosphere is still a target for the researchers. Herein, a Zn2Al-CO3 based layered double hydroxide (LDH) was doped with increasing amounts of Eu3+ (0.01–0.04) and the photocatalytic oxidation of NOx gases was investigated. The LDHs were synthesized by a facile coprecipitation method at room temperature and ambient pressure. The successful Eu3+ substitution in the LDH layers induces a shift in the M−O bonds that modifies the electronic band structure of the doped photocatalysts. Compared to the undoped LDH, the NOx removal efficiency was enhanced by ∼ 17–25 % under UV–Vis light irradiation. Remarkably, a NOx removal efficiency of ∼ 47 % was attained by the optimally doped LDH under Visible irradiation (420 nm), surpassing raw LDH (∼ 9 %). Moreover, the Eu3+ doped LDHs retained its photocatalytic efficiency during long periods of irradiation during consecutive tests with high selectivity (>90 %). Photoluminescence studies indicated that Eu3+ was located in a non-centrosymmetric position, thereby producing structural disorder within the lattice. Eu doping promoted charge separation and a higher production of ⋅OH radicals as verified by time-resolved photoluminescence and electron paramagnetic resonance, respectively. We believe this work reports unprecedent results obtained by Eu-doping of Zn2Al-based LDHs under visible light for NOx photooxidation and serves as a new strategy to prepare functional LDHs for other photocatalytic applications.
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Sep 2023
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[21726]
Open Access
Abstract: Two isostructural hydrogen-bonded organic frameworks (HOFs) with 1-D hexagonal-shaped pores were crystallised using the molecules biphenyl-3,3′,5,5′-tetracarboxylic acid (BPTCA) and [1,1′:4′,1′′]terphenyl- 3,3′′,5,5′′-tetracarboxylic acid (TPTCA). The desolvated HOFs, named BPTCA-2 and TPTCA-2, exhibited selective adsorption towards naphthalene and anthracene, respectively, during competitive adsorption experiments.
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Sep 2023
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[23096]
Abstract: Aerosols contribute to ambient air pollution and, via processes such as cloud droplet formation, affect air quality and climate. Organic compounds often play a major role in aerosol composition, varying with time, location, season, and environment. Cooking food releases fatty acids into the air, and cooking emissions contribute around 10% to UK emissions of PM2.5 (aerosols up to two and a half microns wide). These aerosol particles can be deposited onto surfaces such as windows. A thin, layered film of material builds up over time, creating a persistent crust that is only slowly broken down by other chemicals in the atmosphere. In work recently selected as the best 2022 paper in Environmental Science: Atmospheres, a team led by researchers at the University of Birmingham created ultra-thin films, just a few tens of nanometres in thickness, approximating real-world pollution samples. Using X-ray and neutron techniques to study the nanoscale composition of the films and the changes in their surface structures as they aged, the researchers found that the self-organised layered structure can trap toxic pollutants and form a barrier that can prevent their breakdown. They also showed that the film's surface becomes rougher and attracts more water from humidity, an effect with implications for the formation and lifetime of aerosols in the atmosphere.
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Sep 2023
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B18-Core EXAFS
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Diamond Proposal Number(s):
[24074]
Open Access
Abstract: Historical operations at nuclear mega-facilities such as Hanford, USA, and Sellafield, UK have led to a legacy of radioactivity-contaminated land. Calcium phosphate phases (e.g., hydroxyapatite) can adsorb and/or incorporate radionuclides, including 90Sr. Past work has shown that aqueous injection of Ca-phosphate-generating solutions into the contaminated ground on both laboratory and field scales can reduce the amount of aqueous 90Sr in the systems. Here, two microbially mediated phosphate amendment techniques which precipitated Ca-phosphate, (i) Ca-citrate/Na-phosphate and (ii) glycerol phosphate, were tested in batch experiments alongside an abiotic treatment ((iii) polyphosphate), using stable Sr and site relevant groundwaters and sediments. All three amendments led to enhanced Sr removal from the solution compared to the sediment-only control. The Ca-citrate/Na-phosphate treatment removed 97%, glycerol phosphate 60%, and polyphosphate 55% of the initial Sr. At experimental end points, scanning electron microscopy showed that Sr-containing, Ca-phosphate phases were deposited on sediment grains, and XAS analyses of the sediments amended with Ca-citrate/Na-phosphate and glycerol phosphate confirmed Sr incorporation into Ca-phosphates occurred. Overall, Ca-phosphate-generating treatments have the potential to be applied in a range of nuclear sites and are a key option within the toolkit for 90Sr groundwater remediation.
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Aug 2023
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B18-Core EXAFS
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Diamond Proposal Number(s):
[13559]
Open Access
Abstract: The past 60+ years of global nuclear activity has resulted a signifcant legacy of radioactive contaminated lands which have high economic costs associated with their remediation. Developing clean-up technologies that are environmentally friendly, economically viable and effective in the long-term is key, with in-situ remediation techniques as an important option. However, questions remain regarding the most favorable methods of remediation, and the long-term stability of any immobilised radionuclide(s). Here, we used sediment microcosms to assess the long-term (300 day) stability of immobilised U and Sr formed during anoxic microbial and chemical treatments, and assessed their stability during re-oxidation scenarios (with oxygen or nitrate additions, 100 days). We used six contrasting treatment approaches which resulted in 89 - >99%, and 65 – 95% removal efficiencies for U and Sr, respectively. These included two Zero Valent Iron (ZVI) based products (NANOFER 25S and Carbo-Iron); a slow-release electron donor (Metals Remediation Compound, MRC) to stimulate U(VI) bioreduction alongside a readily bioavailable electron donor control (lactate/acetate mix); electron donor (lactate/acetate) with elevated sulfate to stimulate metal and sulfate reduction; glycerol phosphate to promote both bioreduction of U(VI) and biomineralization of inorganic U/Sr phopshates; and finally a natural attenuation (no remediation agent added) control. X-ray Absorption Spectroscopy (XAS) revealed that whilst aqueous U was removed from solution via multiple mechanisms including sorption, reduction and incorporation, aqueous Sr was mostly removed via outer sphere complexation mechanisms. Re-oxidation with air led to increased U remobilisation (≤89%) compared to nitrate oxidation (≤73%), but neither oxygen or nitrate re-oxidation led to significant Sr remobilisation (≤38%), suggesting Sr speciation may be stable over extended timescales post remediation. Treatments amended with ZVI or glycerol phosphate not only removed the most U and Sr from solution (>99%) but they also retained the most U and Sr following re-oxidation (retaining ≥75% of the originally added U and Sr). XAS analyses suggests that enhanced immbilisation, as seen in the treatments amended with ZVI or glycerol phosphate, may be due to the U/Sr incorporation into mineral phases (i.e., iron oxyhydorxide and phospate pahses) This suggests that optimal (bio)remediation strategies should target both reduction and biomineralisation mechanisms to facilitate radionuclide-mineral incorporation, promoting longer-term stability.
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Aug 2023
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[23490, 29116]
Abstract: A transient pore-scale model of particle deposit formation in 3D microstructure of a catalytic filter wall is introduced. It predicts location of particle deposits, dynamics of their growth, transition from deep to cake filtration regime as well as the impact on flow field, pressure drop and filtration efficiency. The model is validated against time-resolved X-ray tomography (XRT) data acquired during a filtration experiment. The validated model is then used in transient simulations of the soot filtration process in several different microstructures using cordierite filter substrate with varied Pd/-AlO catalyst distribution. The sample with the coating solely inside the wall pores provides the lowest initial pressure drop but suffers from low clean filtration efficiency and high pressure drop after the cake is formed. The sample with partial on-wall coating achieves not only a higher filtration efficiency but also a lower pressure drop in long-term operation.
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Aug 2023
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B18-Core EXAFS
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Diamond Proposal Number(s):
[11156]
Open Access
Abstract: Pb/Zn smelter slag is a hazardous industrial waste from the Imperial Smelting Process (ISP). The speciation of zinc, lead, copper and arsenic in the slag controls their recovery or fate in the environment but has been little investigated. X-ray Absorption Spectroscopy (XAS) was applied to this complex poorly crystalline material for the first time to gain new insights about speciation of elements at low concentration. Zn, Cu, As K-edge and Pb L3-edge XAS was carried out for a Pb/Zn slag from a closed ISP facility in England, supported by Fe, S and P K-edge XAS. Results are presented in the context of a full review of the literature. X-ray fluorescence showed that concentrations of Zn, Pb, Cu and As were 8.4, 1.6, 0.48 and 0.45 wt.%, respectively. Wüstite (FeO) was the only crystalline phase identified by X-ray diffraction, but XAS provided a more complete understanding of the matrix. Zn was found to be mainly present in glass, ZnS, and possibly solid solutions with Fe oxides; Pb was mainly present in glass and apatite minerals (e.g., Pb5(PO4)3OH); Cu was mainly speciated as Cu2S, with some metallic Cu and a weathering product, Cu(OH)2; As speciation was likely dominated by arsenic (III) and (V) oxides and sulfides.
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Aug 2023
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B18-Core EXAFS
I14-Hard X-ray Nanoprobe
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Diamond Proposal Number(s):
[21655, 29037]
Abstract: Air pollutant emission standards and limits were established as a measure to control pollution levels. This has led to novel solutions to meet the ever-
tightening standards, especially towards the size and quantity of particulate matter (PM), particularly ash, emissions. Recent emission standards by the European Union (EU6c), have focused on reducing the PM emissions from gasoline engines. Gasoline particulate filters (GPF) technologies which use a three-way catalyst (TWC) washcoat applied onto the particulate filter, are expected to be implemented to comply with regulatory limits.
Challenges with this system include understanding the role of the ash deposition on the catalyst washcoat and how it affects the catalytic performance. Thus, by observing how the ash interacts within particulate filters, the distribution of metal catalyst and how the regeneration of the catalyst affects performance are key towards improving aftertreatment technology. This project is focused on the analysis of GPF containing mainly PdRh/CeZrOx - La/Al2O3 (TWC) catalyst, using synchrotron-based techniques and imaging, to understand the effect of ageing (simulating use of >100 000 km) and ash deposition on the system. This project explored using
Operando XAS, which was utilised to understand the evolution of Pd during operation conditions and found that with the presence of ash the light-off temperature for CO oxidation and NO reduction increased.
On aged GPF’s, various length scale imaging techniques were performed on the same sample (to retaining spatial resolution), such as XRM, EPMA, FIB-SEM, XRF and AC-STEM and correlated. Nanoprobe XRF mapping and AC-STEM-EDS, suggest formation of large Pd species upon ageing and further co-location of Zn species (introduced by ash deposition) about engine aged ash containing samples. Further, the use of spatially resolved Zn K- edge XANES highlighted that multiple zinc compounds were present from the ash, which reacted with the catalyst upon ageing, forming a zinc spinel analogue.
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Aug 2023
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