B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
E01-JEM ARM 200CF
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Jianwei
Li
,
Kit
Mccoll
,
Xuekun
Lu
,
Sanjay
Sathasivam
,
Haobo
Dong
,
Liqun
Kang
,
Zhuangnan
Li
,
Siyu
Zhao
,
Andreas G.
Kafizas
,
Ryan
Wang
,
Dan J. L.
Brett
,
Paul R.
Shearing
,
Furio
Corà
,
Guanjie
He
,
Claire J.
Carmalt
,
Ivan P.
Parkin
Diamond Proposal Number(s):
[24197, 22572]
Abstract: Cost‐effective and environment‐friendly aqueous zinc‐ion batteries (AZIBs) exhibit tremendous potential for application in grid‐scale energy storage systems but are limited by suitable cathode materials. Hydrated vanadium bronzes have gained significant attention for AZIBs and can be produced with a range of different pre‐intercalated ions, allowing their properties to be optimized. However, gaining a detailed understanding of the energy storage mechanisms within these cathode materials remains a great challenge due to their complex crystallographic frameworks, limiting rational design from the perspective of enhanced Zn2+ diffusion over multiple length scales. Herein, a new class of hydrated porous δ‐Ni0.25V2O5.nH2O nanoribbons for use as an AZIB cathode is reported. The cathode delivers reversibility showing 402 mAh g−1 at 0.2 A g−1 and a capacity retention of 98% over 1200 cycles at 5 A g−1. A detailed investigation using experimental and computational approaches reveal that the host “δ” vanadate lattice has favorable Zn2+ diffusion properties, arising from the atomic‐level structure of the well‐defined lattice channels. Furthermore, the microstructure of the as‐prepared cathodes is examined using multi‐length scale X‐ray computed tomography for the first time in AZIBs and the effective diffusion coefficient is obtained by image‐based modeling, illustrating favorable porosity and satisfactory tortuosity.
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Feb 2020
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E01-JEM ARM 200CF
E02-JEM ARM 300CF
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Diamond Proposal Number(s):
[20892, 20650]
Abstract: Zeolite encapsulated metal nanoparticle catalysts hold great promise for several green and sustainable processes, ranging from environmental remediation to renewable energy and biomass conversion. In particular, the microporous zeolite framework keeps the nanoparticles in a firm grip that can control selectivity and prevent sintering at high temperatures. While progress in the synthesis of mesoporous zeolites continues, the encapsulation of metal nanoparticles remains a challenge that often requires complex procedures and expensive additives. Here, we report a general method to encapsulate both base and noble metal nanoparticles inside the internal voids of a compartmentalized mesoporous zeolite prepared by carbon templating and steam-assisted recrystallization. This results in a remarkable shell-like morphology that facilitates the formation of small metal nanoparticles upon simple impregnation and reduction. When the materials are applied in catalysis, we for instance demonstrate that zeolite encapsulated Ni nanoparticles are highly active, selective and stable catalysts for CO2 methanation (49% conversion with 93% selectivity at 450°C). A reaction where catalysts often suffer from sintering due to the high reaction temperatures. While the introduction of Ni nanoparticles prior to the steam-assisted recrystallization results in the formation of inactive nickel phyllosilicates, noble metals such as Pt do not suffer from this limitation. Therefore, we also demonstrate the synthesis of an active catalyst prepared by the formation of Pt nanoparticles prior to the shell synthesis. We tested the zeolite encapsulated Pt nanoparticles for hydrogenation of linear and cyclic alkenes with increased chain length. The catalysts are active for hydrogenation of oct-1-ene (66% conversion) and cyclooctene (79% conversion) but inactive for the large cyclododecane (<1% conversion), which show that this type of catalyst is highly selective in size selective catalysis. All catalysts are characterized by XRD, TEM, XPS and N2 physisorption.
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Dec 2019
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B18-Core EXAFS
E01-JEM ARM 200CF
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Diamond Proposal Number(s):
[15151]
Open Access
Abstract: Mechanochemistry offers a solventless, ‘waste free’ route to preparing metal oxide catalysts, however, there is limited information on the chemical steps involved. In this work, the perovskite LaMnO3 has been successfully synthesized via mechanochemistry from metal oxide powders, La2O3 and Mn2O3, at room temperature, using a planetary ball mill. Separate ex situ ‘time slices’ were taken during the milling procedure to provide insights into the underlying chemistry. The crystalline material was assessed using XRD, which identified 100% perovskite phase after 3 h of milling. Conversely, characterization by X-ray absorption spectroscopy (XAS) at both the Mn K-edge and La L3-edge provides a very different picture. The XAS data shows that there are significant structural alterations as early as 30 min of milling, with the La precursor dispersed over Mn2O3. Increasing milling time then allows for mechanical activation of both precursors and the formation of powdered LaMnO3, with no calcination step required. The XAS highlights that there is a significant amount of amorphous, oxygen deficient, content even when XRD has identified 100% perovskite phase. The samples were tested for the decomposition of the environmental pollutant N2O; at a milling time of 3 h, the LaMnO3 catalyst displays a much early onset production of N2 compared to a traditional sol–gel synthesized LaMnO3, resulting from increased oxygen deficiency at the surface, confirmed by XPS and STEM-EELS. This is an encouraging sign that mechanochemical routes can be harnessed to provide a sustainable route to preparing mixed metal oxide catalysts with enhanced catalytic performance.
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Dec 2019
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
B18-Core EXAFS
E01-JEM ARM 200CF
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Rosa
Arrigo
,
Simone
Gallarati
,
Manfred E.
Schuster
,
Jake
Seymour
,
Diego
Gianolio
,
Ivan
Da Silva
,
June
Callison
,
Haosheng
Feng
,
John E.
Proctor
,
Pilar
Ferrer
,
Federica
Venturini
,
Dave
Grinter
,
Georg
Held
Open Access
Abstract: Unsupported and SiO 2 ‐supported Ni nanoparticles (NPs), were synthesised via hot‐injection colloidal route using oleylamine (OAm) and trioctylphosphine (TOP) as reducing and protective agents, respectively. By adopting a multi‐length scale structural characterization, it was found that by changing equivalents of OAM and TOP not only the size of the nanoparticles is affected but also the Ni electronic structure. The synthetized NPs were modified with ( R , R )‐tartaric acid (TA) and investigated in the asymmetric hydrogenation of methyl acetoacetate to chiral methyl‐3‐hydroxy butyrate. The comparative analysis of structure and catalytic performance for the synthetized catalysts has enabled us to identify a Ni metallic active surface, whereby the activity increases with the size of the metallic domains. Conversely, at the high conversion obtained for the unsupported NPs there was no impact of particle size on the selectivity. ( R )‐selectivity was very high only on catalysts containing positively charged Ni species such as over the SiO 2 ‐supported NiO NPs. This work shows that the chiral modification of metallic Ni NPs with TA is insufficient to maintain high selectivity towards the ( R )‐enantiomer at long reaction time and provide guidance for the engineering of long‐term stable enantioselective catalysts.
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Dec 2019
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E01-JEM ARM 200CF
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Haohong
Duan
,
Jin-cheng
Liu
,
Ming
Xu
,
Yufei
Zhao
,
Xue-lu
Ma
,
Juncai
Dong
,
Xusheng
Zheng
,
Jianwei
Zheng
,
Christopher
Allen
,
Mohsen
Danaie
,
Yung-kang
Peng
,
Titipong
Issariyakul
,
Dongliang
Chen
,
Angus
Kirkland
,
Jean-charles
Buffet
,
Jun
Li
,
Shik Chi Edman
Tsang
,
Dermot
O'hare
Diamond Proposal Number(s):
[16969, 17397]
Abstract: Although molecular dinitrogen (N2) is widely used as a carrier or inert gas for many catalytic reactions, it is rarely considered as a catalytic promoter. Here, we report that N2 could be used to reduce the activation energy for catalytic hydrodeoxygenation over ruthenium-based catalysts. Specifically, we report a 4.3-fold activity increase in the catalytic hydrodeoxygenation of p-cresol to toluene over a titanium oxide supported ruthenium catalyst (Ru/TiO2) by simply introducing 6 bar N2 under batch conditions at 160 °C and 1 bar hydrogen. Detailed investigations indicate that N2 can be adsorbed and activated on the metallic ruthenium surface to form hydrogenated nitrogen species, which offer protic hydrogen to lower the activation energy of direct carbonaromatic–oxygen bond scission and the hydrogenation of hydroxy groups. Thus, by employing different ruthenium catalysts, including Ru/TiO2, Ru/Al2O3, Ru/ZrO2 and Ru/C, we demonstrate that N2 promotion of hydrodeoxygenation can be regarded as a general strategy.
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Oct 2019
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E01-JEM ARM 200CF
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Diamond Proposal Number(s):
[16854]
Abstract: 2D crystals are typically uniform and periodic in‐plane with stacked sheet‐like structure in the out‐of‐plane direction. Breaking the in‐plane 2D symmetry by creating unique lattice structures offers anisotropic electronic and optical responses that have potential in nanoelectronics. However, creating nanoscale‐modulated anisotropic 2D lattices is challenging and is mostly done using top‐down lithographic methods with ≈10 nm resolution. A phase transformation mechanism for creating 2D striated lattice systems is revealed, where controlled thermal annealing induces Se loss in few‐layered PdSe2 and leads to 1D sub‐nm etched channels in Pd2Se3 bilayers. These striated 2D crystals cannot be described by a typical unit cells of 1–2 Å for crystals, but rather long range nanoscale periodicity in each three directions. The 1D channels give rise to localized conduction states, which have no bulk layered counterpart or monolayer form. These results show how the known family of 2D crystals can be extended beyond those that exist as bulk layered van der Waals crystals by exploiting phase transformations by elemental depletion in binary systems.
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Sep 2019
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E01-JEM ARM 200CF
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Open Access
Abstract: N2O is an extremely potent greenhouse gas that has been shown to have devastating effects on the atmosphere. There are many natural and anthropogenic sources of N2O emissions, such as oceans, atmospheric chemical reactions, industrial chemical processes, by-product from fuel combustion, and contributions from the agricultural sector. Therefore a catalyst that converts N2O into N2 and O2 at low temperatures is highly desirable. Throughout this thesis the common aim is to produce a catalyst that can decompose N2O at temperatures lower than 300 °C. Three different classes of catalysts were investigated in this thesis, the first is a Fe-ZSM-5 catalyst. The work focusses on the effect of different Fe species in Fe-ZSM-5 for the decomposition of N2O in the presence and absence of a reductant, propane. The effect of Si:Al ratio and Fe weight loading was initially investigated before focussing on a single weight loading and the effects of acid washing on catalyst activity and iron speciation. The second class of catalysts were based on Pd-Al2O3 with the focus being on the importance of surface species and particle size of Pd for the decomposition of N2O. The effect of removal of surface species such as water and chloride ions were investigated by different catalyst pre-treatments and support pre-treatments. Through pre-treatment of the catalyst support prior to metal deposition, catalytic activity significantly increased, resulting in a decrease of the T100 by 150 °C to 400 °C. The third class of catalysts studied were a range of perovskite structured materials. Most notably studying how the surface area, phase purity and oxygen species present effected the catalytic activity. The factors were investigated by changing the ratio of elements in the A and B sites, which lead to increased perovskite purities requiring lower calcination temperatures leading to higher surface areas. The ratios that produced the highest phase purity were prepared by two alternative preparation method to the original citric acid preparation, supercritical anti-solvent preparation and oxalic acid preparation.
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Sep 2019
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B18-Core EXAFS
E01-JEM ARM 200CF
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Margherita
Macino
,
Alexandra J.
Barnes
,
Sultan M.
Althahban
,
Ruiyang
Qu
,
Emma K.
Gibson
,
David J.
Morgan
,
Simon J.
Freakley
,
Nikolaos
Dimitratos
,
Christopher J.
Kiely
,
Xiang
Gao
,
Andrew M.
Beale
,
Donald
Bethell
,
Qian
He
,
Meenakshisundaram
Sankar
,
Graham J.
Hutchings
Diamond Proposal Number(s):
[15151, 22776]
Abstract: The catalytic activities of supported metal nanoparticles can be tuned by appropriate design of synthesis strategies. Each step in a catalyst synthesis method can play an important role in preparing the most efficient catalyst. Here we report the careful manipulation of the post-synthetic heat treatment procedure—together with control over the metal loading—to prepare a highly efficient 0.2 wt% Pt/TiO2 catalyst for the chemoselective hydrogenation of 3-nitrostyrene. For Pt/TiO2 catalysts with 0.2 and 0.5 wt% loading levels, reduction at 450 °C induces the coverage of TiOx over Pt nanoparticles through a strong metal–support interaction, which is detrimental to their catalytic activities. However, this can be avoided by following calcination treatment with reduction (both at 450 °C), allowing us to prepare an exceptionally active catalyst. Detailed characterization has revealed that the peripheral sites at the Pt/TiO2 interface are the most likely active sites for this hydrogenation reaction.
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Sep 2019
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E01-JEM ARM 200CF
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Hui
Luo
,
Nikolaos
Papaioannou
,
Enrico
Salvadori
,
Maxie
Roessler
,
Gereon
Ploenes
,
Ernst R. H.
Van Eck
,
Liviu
Tanase
,
Jingyu
Feng
,
Yiwei
Sun
,
Yan
Yang
,
Mohsen
Danaie
,
Ana
Jorge Sobrido
,
Andrei
Sapelkin
,
James
Durrant
,
Stoichko D.
Dimitrov
,
Maria-magdalena
Titirici
Diamond Proposal Number(s):
[17587]
Abstract: As a new class of sustainable carbon material, the term “carbon dots” represents an “umbrella term” as there are many types of materials included. We employ a broad range of techniques to develop understanding on hydrothermally synthesized carbon dots and show how fine tuning the structural features using simple reduction/oxidation reactions can drastically affect their excited state properties. Structural and spectroscopic studies found that photoluminescence originates from direct excitation of localized fluorophores involving oxygen functional groups, while the excitation at graphene‐like features leads to ultrafast phonon‐assisted relaxation and largely quenches the fluorescent quantum yields. This is arguably the first to identify the dynamics of photoluminescence including Stokes’ shift formation, allowing us to fully resolve the relaxation pathways in these carbon dots. The comprehensive investigation sheds light on how understanding the excited state relaxation processes in different carbon structure is crucial for tuning the optical properties for any potential commercial applications.
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Aug 2019
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E01-JEM ARM 200CF
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Diamond Proposal Number(s):
[18909]
Abstract: The hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) is a key reaction for the production of renewable chemicals and fuels, wherein acid-resistant and robust catalysts are highly desired for practical usage. Herein, an ultra-stable 0.6 wt% Ir@ZrO2@C single-atom catalyst was prepared via an in-situ synthesis approach during the assembly of UiO-66, followed by confined pyrolysis. The Ir@ZrO2@C offered not only a quantitative LA conversion and an excellent GVL selectivity (>99%), but also an unprecedented stability during recycling runs under harsh conditions (at T = 453 K, PH2 = 40 bar in pH = 3 or pH = 1 aqueous solution). By thorough spectroscopy characterizations, a well-defined structure of atomically dispersed Irδ+ atoms onto nano-tetragonal ZrO2 confined in the amorphous carbon was identified for the Ir@ZrO2@C. The strong metal-support interaction and the confinement of the amorphous carbon account for the ultra-stability of the Ir@ZrO2@C.
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May 2019
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