B18-Core EXAFS
|
Nicola
Schiaroli
,
Leila
Negahdar
,
Mads
Lützen
,
Phuoc
Hoang Ho
,
Lisa J.
Allen
,
Alejandro
Natoli
,
Francesca
Ospitali
,
Francesco
Maluta
,
Enrique
Rodríguez-Castellón
,
Christian D.
Damsgaard
,
Giuseppe
Fornasari
,
Andrew M.
Beale
,
Patricia
Benito
Abstract: Pd-In2O3 catalysts are among the most promising alternatives to Cu-ZnO-Al2O3 for synthesis of CH3OH from CO2. However, the intrinsic activity and stability of In2O3 per unit mass should be increased to reduce the content of this scarcely available element and to enhance the catalyst lifetime. Herein, we propose and demonstrate a strategy for obtaining highly dispersed Pd and In2O3 nanoparticles onto an Al2O3 matrix by a one-step coprecipitation followed by calcination and activation. The activity of this catalyst is comparable with that of a Pd-In2O3 catalyst (0.52 vs. 0.55 gMeOH h-1 gcat-1 at 300°C, 30 bar, 40,800 ml h-1 gcat-1) but the In2O3 loading decreases from 98 to 12 wt.% while improving the long-term stability by three-fold at 30 bar. In the new Pd-In2O3-Al2O3 system, the intrinsic activity of In2O3 is highly increased both in terms of STY normalized to In specific surface area and In2O3 mass (4.32 vs 0.56 g gMeOH h-1 gIn2O3-1 of a Pd- In2O3 catalyst operating at 300°C, 30 bar, 40,800 ml h-1 gcat-1).The combination of ex situ and in situ catalyst characterizations during reduction provides insights into the interaction between Pd and In and with the support. The enhanced activity is likely related to the close proximity of Pd and In2O3, wherein the H2 splitting activity of Pd promotes, in combination with CO2 activation over highly dispersed In2O3 particles, facile formation of CH3OH.
|
May 2023
|
|
I20-Scanning-X-ray spectroscopy (XAS/XES)
|
Yue
Pang
,
Nils
Nöthling
,
Markus
Leutzsch
,
Liqun
Kang
,
Eckhard
Bill
,
Maurice
Van Gastel
,
Edward
Reijerse
,
Richard
Goddard
,
Lucas
Wagner
,
Daniel
Santalucia
,
Serena
Debeer
,
Frank
Neese
,
Josep
Cornella
Diamond Proposal Number(s):
[30449]
Abstract: Large Spin-Orbit Coupling (SOC) is an intrinsic property of the heavy-elements that directly affects the electronic structures of the compounds. Herein we report the synthesis and characterization of a mono-coordinate bismuthinidene featuring a rigid and bulky ligand. All magnetic measurements (SQUID, NMR) point to a diamagnetic compound. However, multiconfigurational quantum chemical calculations predict the ground state of the compound to be dominated (76%) by a spin-triplet. The apparent diamagnetism is explained by an extremely large SOC induced positive zero-field-splitting of more than 4500 cm−1 that leaves the MS = 0 magnetic sublevel thermally isolated in the electronic ground state.
|
May 2023
|
|
I18-Microfocus Spectroscopy
|
Ivan N.
Pidchenko
,
John N.
Christensen
,
Martin
Kutzschbach
,
Konstantin
Ignatyev
,
Ignasi
Puigdomenech
,
Eva-Lena
Tullborg
,
Nick M. W.
Roberts
,
E. Troy
Rasbury
,
Paul
Northrup
,
Ryan
Tappero
,
Kristina O.
Kvashnina
,
Thorsten
Schäfer
,
Yohey
Suzuki
,
Henrik
Drake
Diamond Proposal Number(s):
[28254]
Open Access
Abstract: Uptake of uranium (U) by secondary minerals, such as carbonates and iron (Fe)-sulfides, that occur ubiquitously on Earth, may be substantial in deep anoxic environments compared to surficial settings due to different environment-specific conditions. Yet, knowledge of U reductive removal pathways and related fractionation between 238U and 235U isotopes in deep anoxic groundwater systems remain elusive. Here we show bacteria-driven degradation of organic constituents that influences formation of sulfidic species facilitating reduction of geochemically mobile U(VI) with subsequent trapping of U(IV) by calcite and Fe-sulfides. The isotopic signatures recorded for U and Ca in fracture water and calcite samples provide additional insights on U(VI) reduction behaviour and calcite growth rate. The removal efficiency of U from groundwater reaching 75% in borehole sections in fractured granite, and selective U accumulation in secondary minerals in exceedingly U-deficient groundwater shows the potential of these widespread mineralogical sinks for U in deep anoxic environments.
|
Apr 2023
|
|
B16-Test Beamline
DIAD-Dual Imaging and Diffraction Beamline
E01-JEM ARM 200CF
E02-JEM ARM 300CF
I08-Scanning X-ray Microscopy beamline (SXM)
I12-JEEP: Joint Engineering, Environmental and Processing
I13-1-Coherence
I13-2-Diamond Manchester Imaging
I14-Hard X-ray Nanoprobe
|
Open Access
Abstract: Hard dental tissues possess a complex hierarchical structure that is particularly evident in enamel, the most mineralised substance in the human body. Its complex and interlinked organisation at the Ångstrom (crystal lattice), nano-, micro-, and macro-scales is the result of evolutionary optimisation for mechanical and functional performance: hardness and stiffness, fracture toughness, thermal, and chemical resistance. Understanding the physical–chemical–structural relationships at each scale requires the application of appropriately sensitive and resolving probes. Synchrotron X-ray techniques offer the possibility to progress significantly beyond the capabilities of conventional laboratory instruments, i.e., X-ray diffractometers, and electron and atomic force microscopes. The last few decades have witnessed the accumulation of results obtained from X-ray scattering (diffraction), spectroscopy (including polarisation analysis), and imaging (including ptychography and tomography). The current article presents a multi-disciplinary review of nearly 40 years of discoveries and advancements, primarily pertaining to the study of enamel and its demineralisation (caries), but also linked to the investigations of other mineralised tissues such as dentine, bone, etc. The modelling approaches informed by these observations are also overviewed. The strategic aim of the present review was to identify and evaluate prospective avenues for analysing dental tissues and developing treatments and prophylaxis for improved dental health.
|
Apr 2023
|
|
B18-Core EXAFS
|
Diamond Proposal Number(s):
[14239]
Abstract: Pd/C catalysts are widely used for hydrogenation reactions in the chemical industry. One of the reasons for their high activity is the ability of Pd nanoparticles (PdNP) to dissociate H2 and promote H-spillover. Nevertheless, for selective hydrogenation unpromoted Pd/C catalysts show disappointing results. The use of supported Pd single atom (PdSA) catalysts permits to achieve high selectivity. However, PdSA show low activity because they have difficulty in activating H2. A cooperative catalysis between PdNP and PdSA operates for the hydrogenation of alkenes thanks to the H-spillover, which makes it possible to obtain active isolated PdSA-H species. Here, we present experimental and computational results obtained for phenylacetylene hydrogenation on Pd/CNT catalysts showing different PdSA/PdNP ratios. Tuning this ratio allows doubling the activity while reaching high selectivity to styrene at high conversion. DFT calculations suggest that the first coordination sphere of PdSA has a pronounced effect on their reactivity.
|
Apr 2023
|
|
I10-Beamline for Advanced Dichroism
|
Erika
Armenta-Jaime
,
Jorge Alberto
Molina González
,
Karla Patricia
Salas-Martin
,
Raymond
Fan
,
Lo-Yueh
Chang
,
Jeng-Lung
Chen
,
Paul
Steadman
,
Haggeo
Desirena
,
Ateet
Dutt
,
Paul
Olalde-Velasco
,
Silvia E. E
Castillo Blum
Abstract: In this work, we studied the optical properties of Dy-doped Gd2O3 nanoparticles (NPs) before and after their APTES functionalisation. We obtained luminescent Dy@Gd2O3 NPs (0.5, 1, and 5% mol) using a modified Polyol method. Our work describes their detailed structural analysis by FT-IR, XRD, HRTEM, TGA and XAS techniques. Results showed that these systems present a crystalline structure with body-centred cubic cell and particle sizes of 10 nm. The dopant position was inferred as substitutional, through XAS analysis at the M4,5-edges of Gd and Dy and K-edge of O, and in C2 sites, based on photoluminescence studies. The emission spectrum showed a sensitisation by energy transfer of the hypersensitive transition (6F9/2→6H13/2, 572 nm) and a broadband around 510 nm attributed to defects in Gd2O3. An enhanced emissive lifetime of 398 µs was found for the sample doped at 1%. We found that these NPs conserved their luminescence after adding the surface agent, making them potential materials for biosensing applications.
|
Apr 2023
|
|
B18-Core EXAFS
|
Diamond Proposal Number(s):
[14239]
Open Access
Abstract: Optimisation of electrodeposition routes of birnessite manganese dioxide (MnO2) coatings onto 3D graphene foam substrates enabled greater attainable capacitances. Current pulse deposition method resulted in highest achievable areal capacitance of 530 mF/cm2 under a 10 mA/cm2 current rate, cycling performance with 91% retention after 9000 cycles, as well as improved rate capability when compared to the cyclic voltammetry or galvanostatic deposition. Introduction of oxygen functional groups to the graphene foam added initial pseudocapacitance and accelerated the rate for nucleation and growth of the MnO2 crystal grains, resulting in an areal capacitance of 410 mF/cm2 under a 10 mA/cm2 current rate. However, in this case the increase in specific capacitance was accompanied by sluggish kinetic for charge storage seen via impedance spectroscopy. The charge storage mechanism of the deposited MnO2 films was investigated using in situ Raman microscopy and analysis of peak shifts revealed expansion and contraction of birnessite MnO2, relating to exchange of Na+ and H2O at the MnO2 interface.
|
Apr 2023
|
|
B18-Core EXAFS
|
Abstract: One of the most ambitious aims of a chemist is the development and comprehensive
understanding of synthetic approaches to finely control reaction pathways and, ultimately,
chemical reactions’ outcomes. A promising strategy that has been adopted to pursue this
goal is the confinement of reactions within confined spaces, i.e. enclosed volumes in the
nanometer scale range with limited accessibility, employed as nanoreactors. Within this
framework, this Ph.D. Thesis investigated differently sized enclosed environments as
reactors for the spatially controlled synthesis of inorganic systems, with the aim of
evaluating the effects of space confinement on the syntheses outcomes. In particular,
different classes of inorganic materials, encompassing metal oxides (MoO3 and undoped
and Eu-doped CaMoO4) and metal nanoparticles (Pd), were synthesized in the increasingly
constrained environment of i) a continuous-flow microreactor, ii) nanodroplets produced
by inverse (water-in-oil) miniemulsions, and iii) nanopores of mesoporous silica materials.
Moreover, the effects of the differently sized confined spaces were evaluated by comparing
the constrained synthesis outcomes with those obtained in a macroreactor (batch
approach). The systematic and comprehensive experimental approach was supported by a
wide array of characterization techniques, from the compositional, structural, dimensional,
and functional point of view, exploiting both ex situ laboratory techniques and more
advanced in situ studies, performed at synchrotron facilities in a time-resolved fashion.
|
Apr 2023
|
|
B18-Core EXAFS
I20-Scanning-X-ray spectroscopy (XAS/XES)
|
Diamond Proposal Number(s):
[21441]
Abstract: In the UK, the decommissioning of legacy spent fuel storage facilities at the Sellafield nuclear facility requires the retrieval of radioactive sludge resulting from Magnox fuel corrosion. However, sludge retrievals may enhance uranium mobility including via sorption of radionuclide nanoparticles onto colloidal phases such as hydrotalcite (Mg4Al2(OH)16(CO3).4H2O). Hydrotalcite is a Mg-Al layered double hydroxide (LDH) which is a corrosion product of Magnox fuel cladding. Currently, there are a paucity of studies examining interactions between actinide nanoparticles and LDH phases such as hydrotalcite. Here, a multi-technique approach was used to investigate the interactions between colloidal hydrotalcite and three different forms of nanoparticulate U(IV): nanoparticulate uraninite (UO2); nanoparticulate UO2 reacted with silica (UO2-Si); and U(IV)-Si-coprecipitate under anoxic, neutral-to-alkaline conditions. Ultrafiltration and zeta potential analyses indicated that for UO2 and UO2-Si nanoparticulate phases, sorption to colloidal hydrotalcite was limited due to rapidly settling UO2 and UO2-Si aggregates (>450 nm). By contrast, ultrafiltration and zeta potential analyses confirmed the U(IV)-Si-coprecipitate nanoparticle phase showed significantly higher sorption to colloidal hydrotalcite. This was due to the increased colloidal stability of intrinsic U(IV)-silicate nanoparticles which in turn promoted increased sorption to hydrotalcite. TEM imaging showed some evidence for smaller UO2 and UO2-Si aggregates (<20 nm) sorbed to colloidal hydrotalcite. Similar behaviour was observed in TEM images of authentic pond effluent samples from Sellafield, providing confidence that the model laboratory experiments provided a bridge to the highly radioactive spent nuclear fuel pond interactions. This study highlights the potential for U(IV) nanoparticles to form a new type of colloid-colloid interaction with hydrotalcite, especially when silica is present. This further informs predictions of U(IV) (and An(IV)) behaviour in the legacy pond and silo environments, as well as in environmental scenarios where LDH mineral phases and silica are present (e.g. in geological disposal of radioactive waste).
|
Apr 2023
|
|
I20-EDE-Energy Dispersive EXAFS (EDE)
|
Xiaoqiang
Liang
,
Sen
Wang
,
Jingyu
Feng
,
Zhen
Xu
,
Zhenyu
Guo
,
Hui
Luo
,
Feng
Zhang
,
Wen
Chen
,
Lei
Feng
,
Chengan
Wan
,
Maria-Magdalena
Titirici
Diamond Proposal Number(s):
[28663]
Abstract: Electrocatalytic oxygen evolution reaction (OER) under neutral or near-neutral conditions has attracted research interest due to its environmental friendliness and economic sustainability in comparison with currently available acidic and alkaline conditions. However, it is challenging to identify electrocatalytically active species in the OER procedure under neutral environments due to non-crystalline forms of catalysts. Crystalline metal-organic framework (MOF) materials could provide novel insights into electrocatalytical active species because of their well-defined structures. In this study, we synthesized two isostructural two-dimensional (2D) MOFs [Co(HCi)2(H2O)2·2DMF]n (Co-Ci-2D) and [Ni(HCi)2(H2O)2·2DMF]n (Ni-Ci-2D) (H2Ci = 1H-indazole-5-carboxylic acid, DMF = N, N-Dimethyl-formamide) to investigate their OER performance in a neutral environment. Our results indicate that Co-Ci-2D holds a current density of 3.93 mA cm-2 at 1.8 V vs. RHE and a OER durability superior to the benchmark catalyst IrO2. Utilizing the advantages of structural transformation of MOF materials which are easier to characterize and analyze compared to ill-defined amorphous materials, we found out that a mononuclear coordination compound [Co(HCi)2(H2O)4] (Co-Ci-mono-A) and its isomer (Co-Ci-mono-B) were proven to be active species of Co-Ci-2D in the neutral OER process. For Ni-Ci-2D, mononuclear coordination compounds similar to structures of the cobalt material (Ni-Ci-mono-A and Ni-Ci-mono-B) together with NiHPO4 formed by the precipitation were confirmed as active species for the neutral OER catalysis. Additionally, the difference in OER activities between Co-Ci-2D and Ni-Ci-2D, approximately one order of magnitude, originates primarily from the opposite tendency of bond length changes in coordination octahedron after being treated by the PBS solution. These findings contribute to a better comprehension of the OER procedure in the neutral media.
|
Apr 2023
|
|
