High throughput <i>in situ</i> EXAFS instrumentation for the automatic characterization of materials and catalysts

An XAS data acquisition and control system for the in situ analysis of dynamic materials libraries under control of temperature and gaseous environment has been developed. It was integrated at the SRS in Daresbury, UK, beamline 9.3, using a Si (220) monochromator and a 13 element solid state Ge fluorescence detector. The core of the system is an intelligent X, Y, Z, θ positioning system coupled to multi-stream quadrupole mass spectrometry analysis (QMS). The system is modular and can be adapted to other synchrotron radiation beamlines. The entire software control was implemented using Labview and allows the scan of a variety of library sizes, in several positions, angles, gas compositions and temperatures with minimal operator intervention. The system was used for the automated characterization of a library of 91 catalyst precursors containing ternary combinations of Cu, Pt, and Au on γ-Al2O3, and for the evaluation and structural characterization of eight Au catalysts supported on A12O3 and TiO2. Mass spectrometer traces reveal conversion rate oscillations in 6wt % Au/γAl2O3 catalysts. The use of HT experimentation for in situ EXAFS studies demonstrates the feasibility and potential of HT in situ XAFS for synchrotron radiation studies

High-throughput synthesis and characterization of BiMoVOX materials

The high throughput synthesis and characterization of a particular family of ceramic materials, bismuth molybdenum vanadium oxides (BiMoVOX), suitable as inorganic yellow pigments and low temperature oxidation catalysts, is described. Samples, synthesized by calcination and peroxo sol-gel methods, are characterized by X-ray powder diffraction, UV-visible and XAFS spectroscopy. A combined high-throughput XRD/XAFS study of a 54 samples array, with simultaneous refinement of data of both techniques, has been performed. Molybdenum doping of bismuth vanadate results in a phase transition from monoclinic BiV04 to tetragonal Bi(V,Mo)04, both of scheelite type. Both central metals, V5+ and Mo6+, remain in a tetrahedral coordination. UV/visible spectroscopy identifies a linear blue shift as a function of Mo6+ amount

High Throughput In Situ XAFS Screening of Catalysts

We outline and demonstrate the feasibility of high-throughput (HT) in situ XAFS for synchrotron radiation studies. An XAS data acquisition and control system for the analysis of dynamic materials libraries under control of temperature and gaseous environments has been developed. The system is compatible with the 96-well industry standard and coupled to multi-stream quadrupole mass spectrometry (QMS) analysis of reactor effluents. An automated analytical workflow generates data quickly compared to traditional individual spectrum acquisition and analyses them in quasi-real time using an HT data analysis tool based on IFFEFIT. The system was used for the automated characterization of a library of 91 catalyst precursors containing ternary combinations of Cu, Pt, and Au on ?-Al2O3, and for the in situ characterization of Au catalysts supported on Al2O3 and TiO2

Mining of nickel laterites – towards more environmentally responsible operations

Primary mining of technology metal ores is needed to enable effective decarbonisation. The use of nickel in rechargeable batteries is expected to increase global demand for nickel rapidly over the coming years. Over 60% of annual global nickel production originates from nickel laterites, with Indonesia and the Philippines leading the market. Mining of nickel laterite ore can adversely affect the environment through the release of CO2 and potentially hazardous elements (PHE), such as hexavalent chromium, or asbestiform minerals. Through our better understanding of the social and environmental impacts of mining operations and the availability of technologies that can potentially mitigate adverse impact, it is paramount to aim for more responsible mining and metal recovery operations. This study focuses on the Sta Cruz nickel laterite deposit in the Philippines. Through a multi-scale and multi-technique analytical programme and drawing on existing knowledge1,2, we appraise the deposit holistically, focusing on (i) the geochemistry and mineralogy of major commodities and trace metals, such as the platinum group elements; (ii) carbonate forming metals, e.g. magnesium and (iii) the presence and ecotoxicity of PHE and minerals. We use this understanding to assess the potential for a circular economy in mining, via complete utilisation of the ore to maximise the metal output and minimise the waste produced. This includes the removal of CO2 through the formation of carbonate minerals (mineral carbonation). We also investigate the potential of carbonates to immobilise chromium crystallographically alongside the CO2. This aspect of mineral carbonation is currently poorly understood. We have carried out laboratory synthesis of chromium-doped carbonates at ambient P-T conditions, which indicates that the most common magnesium carbonates do not readily accommodate chromium. However, other carbonate-bearing minerals, including those belonging to layered double hydroxides, present a viable alternative. The combined PHE-CO2 mineral carbonation, when implemented at different stages of metal recovery, from ore extraction to processing, could lead to a reduction of the volume and toxicity of waste, collectively contributing to the mitigation of the adverse environmental impact of nickel laterite mining. [1] Acquino et al (2022) Minerals, 12(3) [2] Bacuta et al (1990) Journal of Geochem.Exploration, 3

Redox and Ligand Exchange during the Reaction of Tetrachloroaurate with Hexacyanoferrate(II) at a Liquid-Liquid Interface: Voltammetry and X-ray Absorption Fine-Structure Studies

AbstractVoltammetry for charge (ion and electron) transfer at two immiscible electrolyte solutions (VCTIES) has been used to provide insight into the ligand exchange and redox processes taking place during the interfacial reaction of aqueous hexacyanoferrate(II) with tetrachloroaurate ([AuCl4]−) in 1,2-dichloroethane (DCE). VCTIES permitted the detection of the reactants, intermediates and products at the liquid/liquid interface. A model for the sequence of interfacial processes was established with the support of speciation analysis of the key elementary reactions by X-ray absorption spectroscopy (XAS). The potential-driven transfer of [AuCl4]− from the organic into the aqueous phase is followed by reduction and ligand exchange by the aqueous hexacyanoferrate(II) to form dicyanoaurate ([Au(CN)2]−). Inferences from the reactions point to the likely formation of [AuCl2]− during the reduction sequence. The reaction is influenced by ligand exchange equilibria between [AuCl4]−, [AuCl3(OH)]– and [AuCl2(OH)2]– which are shown to be dependent on the chloride ion concentration and pH of the solution. The difference between the Gibbs energy of transfer at the water | DCE interface (ΔGDCEW°)of AuCl4– and [AuCl3(OH)]–, and the difference between [AuCl3(OH)]– and [AuCl2(OH)2]– were found to change by a value close to the difference between ΔGDCEW° of Cl– and that of OH–. The intermediate Au(I) species, [AuCl2]−, was seen to decompose at neutral pH and in the absence of Cl– in water to form metallic Au, although it was stable in >10mM HCl for an hour. Time-dependent VCTIES and X-ray absorption fine structure (XAFS) speciation analysis of the homogeneous aqueous phase indicate that reaction between [AuCl4]− and hexacyanoferrate(II) is accompanied by the formation of an intermediate ionic species, formed when the concentration of [AuCl4]− is close to that of hexacyanoferrate(II). This species, whose identity was not precisely determined, was also generated by reaction between [AuCl2]− and hexacyanoferrate(III). The species is shown by VCTIES to be more hydrophilic than [Au(CN)2]−, [AuCl2]− and [AuCl4]−

The Molecular Basis for Properties of Binary Solvent Systems: Synchrotron X-ray Pair Distribution Function Analysis of the Acetone-Water System

The acetone-water phase diagram. Dynamic structural insights into intermolecular interactions in acetone-water binary mixtures modelled from synchrotron total X-ray scattering describes phase behavior. <br /

Bulk and surface conformations in solid-state lovastatin : Spectroscopic and molecular dynamics studies

Conformational flexibility in molecules can give rise to a range of functional group termi-nations at crystal surfaces and dynamic disorder in the bulk. In this work, we explore the confor-mational behavior of the drug molecule lovastatin in the crystallographically disordered solid and at crystal surfaces through a combination of computational modeling and spectroscopy. Gas-phase and periodic quantum-chemical calculations are used to study the potential energy surface associ-ated with rotatable bonds to examine the disorder in bulk. These calculations are combined with vibrational and X-ray photoelectron spectroscopy measurements to obtain insight into the conformations in bulk and at the surface. Our MD simulations show that the bulk disorder is driven by cooperative motion of the butyl group on the S-butanoate moiety along one crystallographic direc-tion beyond a unit cell. The calculations show that the O-H group can rotate relatively freely between two low-energy conformers in the gas phase but is locked in position by intermolecular H-bonding interactions in the bulk crystal, and we find tentative spectroscopic evidence for the second conformer being present at the surface. We also comment on the relative utility of these different techniques for studying molecular conformation in bulk and at surfaces and highlight possible areas for future developments

Time-Resolved X-ray Phase-Contrast Imaging (XPCI) of Nucleation and Crystal Growth in the Anti-Solvent Crystallization of Lovastatin

X-ray phase contrast imaging (XPCI) of anti-solvent crystallization of lovastatin from an acetone/water solution was carried out in a concentric flow mixing device, using water as the anti-solvent. Spinodal decomposition of the solution is observed to give rise to ‘oiled out’ phases that undergo heterogeneous nucleation at the interface with the flowing solution. Heterogeneous nucleation is also observed on the walls of the reactor walls in the form of what appears to be Stranski–Krastanov growth of plate-like crystals. XPCI together with Eulerian video magnification forms a powerful tool for the spatio-temporal analysis, revealing mechanistic details of a non-equilibrium process such as anti-solvent crystallization.</p

High-throughput structure/function screening of materials and catalysts with multiple spectroscopic techniques

High throughput screening methodologies are expanded to synchrotron based x-ray absorption techniques. An environmental chamber, based on ultra-high vacuum equipment, has been developed allowing in situ studies on arrays of samples while X-ray absorption fine structure spectroscopy, Raman spectroscopy, mass spectrometry and/or Xray diffraction can be applied simultaneously to characterize the system under process conditions in a time-resolved manner. The chamber accommodates a diverse range of samples from surface science to materials chemistry to heterogeneous catalysis. Data acquisition and data logging software is developed to handle large quantities of divers but related information. New data logging, processing and analysis procedures and programs are developed which will allow fast structure-function relationships characterization

UK-XFEL Science Case

Following the Strategic FEL Review in 2016, this draft science case, led by Professor Jon Marangos (Imperial College) sets out the scientific rationale for a potential sovereign machine in the UK