Versatile in situ powder X-ray diffraction cells for solid-gas investigations

Revisiting the hydrogenation behavior of NdGa and its hydride phases

NdGa hydride and deuteride phases were prepared from high-quality NdGa samples and their structures characterized by powder and single-crystal X-ray diffraction and neutron powder diffraction. NdGa with the orthorhombic CrB-type structure absorbs hydrogen at hydrogen pressures ≤ 1 bar until reaching the composition NdGaH(D)1.1, which maintains a CrB-type structure. At elevated hydrogen pressure additional hydrogen is absorbed and the maximum composition recovered under standard temperature and pressure conditions is NdGaH(D)1.6 with the Cmcm LaGaH1.66-type structure. This structure is a threefold superstructure with respect to the CrB-type structure. The hydrogen atoms are ordered and distributed on three fully occupied Wyckoff positions corresponding to tetrahedral (4c, 8g) and trigonal-bipyramidal (8g) voids in the parent structure. The threefold superstructure is maintained in the H-deficient phases NaGaH(D)x until 1.6 ≥ x ≥ 1.2. At lower H concentrations, coinciding with the composition of the hydride obtained from hydrogenation at atmospheric pressure, the unit cell of the CrB-type structure is resumed. This phase can also display H deficiency, NdGaH(D)y (1.1 ≥ y ≥ 0.9), with H(D) exclusively situated in partially empty tetrahedral voids. The phase boundary between the threefold superstructure (LaGaH1.66 type) and the onefold structure (NdGaH1.1 type) is estimated on the basis of phase-composition isotherms and neutron powder diffraction to be x = 1.15.

In situ/operando plug-flow fixed-bed cell for synchrotron PXRD and XAFS investigations at high temperature, pressure, controlled gas atmosphere and ultra-fast heating

A plug-flow fixed-bed cell for synchrotron powder X-ray diffraction (PXRD) and X-ray absorption fine structure (XAFS) idoneous for the study of heterogeneous catalysts at high temperature, pressure and under gas flow is designed, constructed and demonstrated. The operating conditions up to 1000°C and 50 bar are ensured by a set of mass flow controllers, pressure regulators and two infra-red lamps that constitute a robust and ultra-fast heating and cooling method. The performance of the system and cell for carbon dioxide hydrogenation reactions under specified temperatures, gas flows and pressures is demonstrated both for PXRD and XAFS at the P02.1 (PXRD) and the P64 (XAFS) beamlines of the Deutsches Elektronen-Synchrotron (DESY).

Intercalation of CO2 Selected by Type of Interlayer Cation in Dried Synthetic Hectorite

Clay minerals are abundant in caprock formations for anthropogenic storage sites for CO₂, and they are potential capture materials for CO₂ postcombustion sequestration. We investigate the response to CO₂ exposure of dried fluorohectorite clay intercalated with Li⁺, Na⁺, Cs⁺, Ca²⁺, and Ba²⁺. By in situ powder X-ray diffraction, we demonstrate that fluorohectorite with Na⁺, Cs⁺, Ca²⁺, or Ba²⁺ does not swell in response to CO₂ and that Li-fluorohectorite does swell. A linear uptake response is observed for Li-fluorohectorite by gravimetric adsorption, and we relate the adsorption to tightly bound residual water, which exposes adsorption sites within the interlayer. The experimental results are supported by DFT calculations.

In Situ Synchrotron X-ray Diffraction Studies of Hydrogen-Desorption Properties of 2LiBH4-Mg2FeH6 Composite

Adding a secondary complex metal hydride can either kinetically or thermodynamically facilitate dehydrogenation reactions. Adding Mg₂FeH₆ to LiBH₄ is energetically favoured, since FeB and MgB₂ are formed as stable intermediate compounds during dehydrogenation reactions. Such “hydride destabilisation” enhances H₂-release thermodynamics from H₂-storage materials. Samples of the LiBH₄ and Mg₂FeH₆ with a 2:1 molar ratio were mixed and decomposed under three different conditions (dynamic decomposition under vacuum, dynamic decomposition under a hydrogen atmosphere, and isothermal decomposition). In situ synchrotron X-ray diffraction results revealed the influence of decomposition conditions on the selected reaction path. Dynamic decomposition of Mg₂FeH₆–LiBH₄ under vacuum, or isothermal decomposition at low temperatures, was found to induce pure decomposition of LiBH₄, whilst mixed decomposition of LiBH₄ + Mg and formation of MgB₂ were achieved via high-temperature isothermal dehydrogenation.

A simple gas introduction system for cryogenic powder X-ray diffraction

A simple system is described for the introduction of gases into standard X-ray diffraction capillaries mounted in situ in the X-ray beam of laboratory X-ray diffraction instruments. This system retains many of the advantages of the standard Norby cell, but does not require custom machining and has less stringent space restrictions. The system has been used to study the crystallization and interaction of volatile organics at cryogenic temperatures, but gas–solid interactions could also be studied at elevated temperatures using this approach.

Infrared furnace for in situ neutron single-crystal diffraction studies in controlled gas atmospheres at high temperatures

To understand oxygen diffusion mechanisms in non-stoichiometric oxides, the possibility to explore structural changes as a function of the oxygen partial pressure with temperature and related oxygen bulk stoichiometry is mandatory. This article reports on the realization of a high-temperature furnace, suitable for single-crystal neutron diffraction, working continuously at temperatures of up to 1000°C at different and adjustable partial gas pressures of up to 2 bar (1 bar = 100 kPa). This allows exploration of the phase diagrams of non-stoichiometric oxides under in situ conditions and controlled oxygen partial pressure. As a pilot study, the structural changes of Pr2NiO4+δ were explored at room temperature (δ ≃ 0.24) and at 900°C under 1 bar P(O2) (δ ≃ 0.13) as well as under secondary vacuum (approximately 10−5 mbar) conditions yielding a δ close to zero. The strong anharmonic displacements of the apical oxygen atoms along the [110] shallow diffusion pathway, which were previously observed at room temperature and 400°C, become more isotropic at 900°C. The study shows that the anisotropic oxygen displacements, here related to lattice instabilities, play a major role in understanding oxygen diffusion pathways and related activation energies at moderate temperatures. This also shows the importance of the availability of reaction cells for single-crystal neutron diffraction to explore the phase diagram and associated structural changes of non-stoichiometric oxygen ion conductors and respective diffusion mechanisms.

Design and use of a sapphire single-crystal gas-pressure cell for in situ neutron powder diffraction

A gas-pressure cell for in situ neutron powder diffraction based on a sapphire single crystal is described. Materials information, technical drawings and instructions for use are included.

A sapphire single-crystal gas-pressure cell without external support allowing unobstructed optical access by neutrons has been developed and optimized for elastic in situ neutron powder diffraction using hydrogen (deuterium) gas at the high-intensity two-axis diffractometer D20 at the Institut Laue-Langevin (Grenoble, France). Given a proper orientation of the single-crystal sample holder with respect to the detector, parasitic reflections from the sample holder can be avoided and the background can be kept low. Hydrogen (deuterium) gas pressures of up to 16.0 MPa at 298 K and 8.0 MPa at 655 K were tested successfully for a wall thickness of 3 mm. Heating was achieved by a two-sided laser heating system. The typical time resolution of in situ investigations of the reaction pathway of hydrogen (deuterium) uptake or release is on the order of 1 min. Detailed descriptions of all parts of the sapphire single-crystal gas-pressure cell are given, including materials information, technical drawings and instructions for use.

Controlled sample environment for studying solid-gas interactions by in situ powder X-ray diffraction

A sample cell for powder X-ray diffraction studies with in situ applied pressure and control of temperature is demonstrated. The cell is based on a previously reported design and consists of a glass or quartz capillary glued into a Swagelok weld gland; this configuration can hold up to 100 bar (1 bar = 100 kPa). The cell is placed in contact with a copper plate for control of temperature between -30 and 200°C. This is achieved by Peltier elements, heat cartridges and a refrigerated circulating bath. This work mainly focuses on the temperature control system. Commissioning tests were performed in a custom-made small/wide-angle X-ray diffractometer at the Norwegian University of Science and Technology. The system is easily portable to synchrotron facilities.

High-pressure sapphire capillary cell for synchrotron single-crystal X-ray diffraction measurements to 1500 bar

A new sapphire capillary pressure cell for single-crystal X-ray diffraction measurements at moderate pressures (200−1500 bar; 1 bar = 100 kPa) has been developed and optimized for use on beamline I19 at Diamond Light Source. The three-component cell permits optical centring of the crystal and in situ pressure modification to a precision of 1 bar. Compression of hexamethylenetetramine and its deuterated analogue to 1000 bar was performed, showcasing the accuracy and precision of the measurements, and highlighting evidence of a geometric isotope effect.

Fast continuous measurement of synchrotron powder diffraction synchronized with controlling gas and vapour pressures at beamline BL02B2 of SPring-8

A gas- and vapour-pressure control system synchronized with the continuous data acquisition of millisecond high-resolution powder diffraction measurements was developed to study structural change processes in gas storage and reaction materials such as metal organic framework compounds, zeolite and layered double hydroxide. The apparatus, which can be set up on beamline BL02B2 at SPring-8, mainly comprises a pressure control system of gases and vapour, a gas cell for a capillary sample, and six one-dimensional solid-state (MYTHEN) detectors. The pressure control system can be remotely controlled via developed software connected to a diffraction measurement system and can be operated in the closed gas and vapour line system. By using the temperature-control system on the sample, high-resolution powder diffraction data can be obtained under gas and vapour pressures ranging from 1 Pa to 130 kPa in temperatures ranging from 30 to 1473 K. This system enables one to perform automatic and high-throughput in situ X-ray powder diffraction experiments even at extremely low pressures. Furthermore, this developed system is useful for studying crystal structures during the adsorption/desorption processes, as acquired by millisecond and continuous powder diffraction measurements. The acquisition of diffraction data can be synchronized with the control of the pressure with a high frame rate of up to 100 Hz. In situ and time-resolved powder diffraction measurements are demonstrated for nanoporous Cu coordination polymer in various gas and vapour atmospheres.

High-pressure and -temperature spinning capillary cell for in situ synchrotron X-ray powder diffraction

In situ research of materials under moderate pressures (hundreds of bar) is essential in many scientific fields. These range from gas sorption to chemical and biological processes. One industrially important discipline is the hydration of oil well cements. Existing capillary cells in this pressure range are static as they are easy to design and operate. This is convenient for the study of single-phase materials; however, powder diffraction quantitative analyses for multiphase systems cannot be performed accurately as a good powder average cannot be attained. Here, the design, construction and commissioning of a cost-effective spinning capillary cell for in situ powder X-ray diffraction is reported, for pressures currently up to 200 bar. The design addresses the importance of reducing the stress on the capillary by mechanically synchronizing the applied rotation power and alignment on both sides of the capillary while allowing the displacement of the supports needed to accommodate different capillaries sizes and to insert the sample within the tube. This cell can be utilized for multiple purposes allowing the introduction of gas or liquid from both ends of the capillary. The commissioning is reported for the hydration of a commercial oil well cement at 150 bar and 150°C. The quality of the resulting powder diffraction data has allowed in situ Rietveld quantitative phase analyses for a hydrating cement containing seven crystalline phases.

Evolution of intermetallic GaPd2/SiO2 catalyst and optimization for methanol synthesis at ambient pressure

The CO2 hydrogenation to methanol is efficiently catalyzed at ambient pressure by nanodispersed intermetallic GaPd2/SiO2 catalysts prepared by incipient wetness impregnation. Here we optimize the catalyst in terms of metal content and reduction temperature in relation to its catalytic activity. We find that the intrinsic activity is higher for the GaPd2/SiO2 catalyst with a metal loading of 13 wt.% compared to catalysts with 23 wt.% and 7 wt.%, indicating that there is an optimum particle size for the reaction of around 8 nm. The highest catalytic activity is measured on catalysts reduced at 550°C. To unravel the formation of the active phase, we studied calcined GaPd2/SiO2 catalysts with 23 wt.% and 13 wt.% using a combination of in situ techniques: X-ray diffraction (XRD), X-ray absorption near edge fine structure (XANES) and extended X-ray absorption fine structure (EXAFS). We find that the catalyst with higher metal content reduces to metallic Pd in a mixture of H2/Ar at room temperature, while the catalyst with lower metal content retains a mixture of PdO and Pd up to 140°C. Both catalysts form the GaPd2 phase above 300°C, albeit the fraction of crystalline intermediate Pd nanoparticles of the catalyst with higher metal loading reduces at higher temperature. In the final state, the catalyst with higher metal loading contains a fraction of unalloyed metallic Pd, while the catalyst with lower metal loading is phase pure. We discuss the alloying mechanism leading to the catalyst active phase formation selecting three temperatures: 25°C, 320°C and 550°C.

In situ observation of phase changes of a silica-supported cobalt catalyst for the Fischer-Tropsch process by the development of a synchrotron-compatible in situ/operando powder X-ray diffraction cell

In situ characterization of catalysts gives direct insight into the working state of the material. Here, the design and performance characteristics of a universal in situ synchrotron-compatible X-ray diffraction cell capable of operation at high temperature and high pressure, 1373 K, and 35 bar, respectively, are reported. Its performance is demonstrated by characterizing a cobalt-based catalyst used in a prototypical high-pressure catalytic reaction, the Fischer-Tropsch synthesis, using X-ray diffraction. Cobalt nanoparticles supported on silica were studied in situ during Fischer-Tropsch catalysis using syngas, H₂ and CO, at 723 K and 20 bar. Post reaction, the Co nanoparticles were carburized at elevated pressure, demonstrating an increased rate of carburization compared with atmospheric studies.

Low-cost disposable high-pressure setup for in situ X-ray experiments

A low-cost, flexible and fast method to create disposable sample cells suitable for in situ catalytic or material synthesis studies based on standard quartz capillaries, heat-shrinkable tubing and standard Swagelok components is described.

AGES: Automated Gas Environment System for in situ neutron powder diffraction

High fluxes available at modern neutron and synchrotron sources have opened up a wide variety of in situ and operando studies of real processes using scattering techniques. This has allowed the user community to follow chemistry in the beam, which often requires high temperatures, gas flow, etc. In this paper, we describe an integrated gas handling system for the general-purpose powder diffraction beamline Powgen at the Spallation Neutron Source. The Automated Gas Environment System (AGES) allows control of both gas flow and temperature (room temperature to 850 °C), while measuring the partial pressure of oxygen and following the effluent gas by mass spectrometry, concurrent with neutron powder diffraction, in order to follow the structural evolution of materials under these conditions. The versatility of AGES is illustrated by two examples of experiments conducted with the system. In solid oxide fuel cell electrode materials, oxygen transport pathways in double perovskites PrBaCo₂O_5+δ and NdBaCo₂O_5+δ were elucidated by neutron diffraction measurements under atmosphere with oxygen partial pressures (pO₂) of 10^-1 to 10^-4 (achieved using mixtures of nitrogen and oxygen) and temperatures from 575 to 850 °C. In another example, the potential oxygen storage material La_1-xSr_xFeO₃ was measured under alternating flows of 15% CH₄ in N₂ and air (20% O₂ in N₂) at temperatures from 135 to 835 °C. From the oxygen stoichiometry, the optimal composition for oxygen storage was determined.

Development of an in situ synchrotron X-ray total scattering setup under pressurized hydrogen gas

This article describes the development of an in situ gas-loading sample holder for synchrotron X-ray total scattering experiments, particularly for hydrogen storage materials, designed to collect diffraction and pair distribution function (PDF) data under pressurized hydrogen gas. A polyimide capillary with a diameter and thickness of 1.4 and 0.06 mm, respectively, connected with commercially available Swagelok fittings was used as an in situ sample holder. Leakage tests confirmed that this sample holder allows 3 MPa of hydrogen gas pressure and 393 K to be achieved without leakage. Using the developed in situ sample holder, significant background and Bragg peaks from the sample holder were not observed in the X-ray diffraction patterns and their signal-to-noise ratios were sufficiently good. The PDF patterns showed sharp peaks in the r range up to 100 Å. The results of Rietveld and PDF refinements of Ni are consistent with those obtained using a polyimide capillary (1.0 mm diameter and 0.04 mm thickness) that has been used for ex situ experiments. In addition, in situ synchrotron X-ray total scattering experiments under pressurized hydrogen gas up to 1 MPa were successfully demonstrated for LaNi4.6Cu.

Transmission in situ and operando high temperature X-ray powder diffraction in variable gaseous environments

This work describes a device for time-resolved synchrotron-based in situ and operando X-ray powder diffraction measurements at elevated temperatures under controllable gaseous environments. The respective gaseous sample environment is realized via a gas-tight capillary-in-capillary design, where the gas flow is achieved through an open-end 0.5 mm capillary located inside a 0.7 mm capillary filled with a sample powder. Thermal mass flow controllers provide appropriate gas flows and computer-controlled on-the-fly gas mixing capabilities. The capillary system is centered inside an infrared heated, proportional integral differential-controlled capillary furnace allowing access to temperatures up to 1000 °C.

Fluoride substitution in LiBH4; destabilization and decomposition

Fluoride substitution in LiBH₄ is studied by investigation of LiBH₄-LiBF₄ mixtures (9 : 1 and 3 : 1). Decomposition was followed by in situ synchrotron radiation X-ray diffraction (in situ SR-PXD), thermogravimetric analysis and differential scanning calorimetry with gas analysis (TGA/DSC-MS) and in situ infrared spectroscopy (in situ FTIR). Upon heating, fluoride substituted LiBH₄ forms (LiBH_4-xF_x) and decomposition occurs, releasing diborane and solid decomposition products. The decomposition temperature is reduced more than fourfold relative to the individual constituents, with decomposition commencing at T = 80 °C. The degree of fluoride substitution is quantified by sequential Rietveld refinement and shows a selective manner of substitution. In situ FTIR experiments reveal formation of bands originating from LiBH_4-xF_x. Formation of LiF and observation of diborane release implies that the decomposing materials have a composition that facilitates formation of diborane and LiF, i.e. LiBH_4-xF_x (LiBH₃F). An alternative approach for fluoride substitution was performed, by addition of Et₃N·3HF to LiBH₄, yielding extremely unstable products. Spontaneous decomposition indicates fluoride substitution to have occurred. From our point of view, this is the most significant destabilization effect seen for borohydride materials so far.

A flow cell for the study of gas-solid reactions via in situ powder X-ray diffraction

This paper describes the development and testing of a novel capillary flow cell for use in in situ powder X-ray diffraction experiments. It is designed such that it achieves 200° of rotation of the capillary whilst still allowing the flow of gas through the sample and the monitoring of off gas via mass spectrometry, gas chromatography, or other such analytical techniques. This high degree of rotation provides more uniform heating of the sample than can be achieved in static cells or those with lower rotational ranges and consequently also improves particle statistics. The increased uniformity of heating provides more accurate temperature calibration of the experimental setup as well. The cell is designed to be held in a standard goniometer head and is therefore suitable for use in many laboratory and synchrotron instruments.

Metal borohydrides and derivatives – synthesis, structure and properties

A comprehensive review of metal borohydrides from synthesis to application.

Phase diagrams of the LiBH4–NaBH4–KBH4 system

The LiBH₄–NaBH₄–KBH₄ system was explored combining experimental and theoretical techniques to establish phase diagrams and thermodynamic properties in all temperature and composition ranges.

Synthesis, structures and thermal decomposition of ammine MxB12H12complexes (M = Li, Na, Ca)

This work presents the structural and thermal properties of ammine metal dodecahydro-closo-dodecaboranes and their reversible ammonia (or hydrogen) storage.

From M(BH4)3 (M = La, Ce) Borohydride Frameworks to Controllable Synthesis of Porous Hydrides and Ion Conductors

Rare earth metal borohydrides show a number of interesting properties, e.g., Li ion conductivity and luminescence, and the series of materials is well explored. However, previous attempts to obtain M(BH₄)₃ (M = La, Ce) by reacting MCl₃ and LiBH₄ yielded LiM(BH₄)₃Cl. Here, a synthetic approach is presented, which allows the isolation of M(BH₄)₃ (M = La, Ce) via formation of intermediate complexes with dimethyl sulfide. The cubic c-Ce(BH₄)₃ (Fm3̅c) is isostructural to high-temperature polymorphs of A(BH₄)₃ (A = Y, Sm, Er, Yb) borohydrides. The larger size of the Ce³⁺ ion makes the empty void in the open ReO₃-type framework structure potentially accessible to small guest molecules like H₂. Another new rhombohedral polymorph, r-M(BH₄)₃ (M = La, Ce), is a closed form of the framework, prone to stacking faults. The new compounds M(BH₄)₃ (M = La, Ce) can be combined with LiCl in an addition reaction to form LiM(BH₄)₃Cl also known as Li₄[M₄(BH₄)₁₂Cl₄]; the latter contains the unique tetranuclear cluster [M₄(BH₄)₁₂Cl₄]^4- and shows high Li-ion conductivity. This reaction pathway opens a way to synthesize a series of A₄[M₄(BH₄)₁₂X₄] (M = La, Ce) compounds with different anions (X) and metal ions (A) and potentially high ion conductivity.

A new multipurpose diffractometer PILATUS@SNBL

The diffraction beamline BM01A at the European Synchrotron Radiation Facility (CRG Swiss-Norwegian beamlines) has been successfully operational for 20 years. Recently, a new multifunctional diffractometer based on the Dectris Pilatus 2M detector has been constructed, commissioned and offered to users. The diffractometer combines a fast and low-noise area detector, which can be tilted and moved horizontally and vertically, together with flexible goniometry for sample positioning and orientation. The diffractometer is controlled by a user-friendly and GUI-based software Pylatus which is also used to control various auxiliary equipment. The latter includes several heating and cooling devices, in situ cells and complimentary spectroscopic tools.

Metal borohydride formation from aluminium boride and metal hydrides

Formation and quantification of metal borohydrides at high pressure, p(H₂) = 600 bar, and elevated temperature from AlB₂-MH_x (M = Li, Na, Mg, Ca) composites.

A thermodynamic investigation of the LiBH4–NaBH4 system

The LiBH₄–NaBH₄ system was investigated experimentally and theoretically (XRD, TPPA, DSC and ab initio calculations). All collected data and literature values were used for a thermodynamic assessment by the calphad method.

Synthesis and thermal stability of perovskite alkali metal strontium borohydrides

Synthesis of new thermally stable perovskite-type metal strontium borohydrides, MSr(BH₄)₃ (M = K, Rb, Cs).

Ammine Calcium and Strontium Borohydrides: Syntheses, Structures, and Properties

A new series of solvent- and halide-free ammine strontium metal borohydrides Sr(NH3 )n (BH4 )2 (n=1, 2, and 4) and further investigations of Ca(NH3 )n (BH4 )2 (n=1, 2, 4, and 6) are presented. Crystal structures have been determined by powder XRD and optimized by DFT calculations to evaluate the strength of the dihydrogen bonds. Sr(NH3 )(BH4 )2 (Pbcn) and Sr(NH3 )2 (BH4 )2 (Pnc2) are layered structures, whereas M(NH3 )4 (BH4 )2 (M=Ca and Sr; P21 /c) are molecular structures connected by dihydrogen bonds. Both series of compounds release NH3 gas upon thermal treatment if the partial pressure of ammonia is low. Therefore, the strength of the dihydrogen bonds, the structure of the compounds, and the NH3 /BH4 (-) ratio for M(NH3 )n (BH4 )m have little influence on the composition of the released gasses. The composition of the released gas depends mainly on the thermal stability of the ammine metal borohydride and the corresponding metal borohydride.

In situX-ray diffraction environments for high-pressure reactions

New sample environments and techniques specifically designed forin situpowder X-ray diffraction studies up to 1000 bar (1 bar = 105 Pa) gas pressure are reported and discussed. The cells can be utilized for multiple purposes in a range of research fields. Specifically, investigations of gas–solid reactions and sample handling under inert conditions are undertaken here. Sample containers allowing the introduction of gas from one or both ends are considered, enabling the possibility of flow-through studies. Various containment materials are evaluated,e.g.capillaries of single-crystal sapphire (Al2O3), quartz glass (SiO2), stainless steel (S316) and glassy carbon (Sigradur K), and burst pressures are calculated and tested for the different tube materials. In these studies, high hydrogen pressure is generated with a metal hydride hydrogen compressor mounted in a closed system, which allows reuse of the hydrogen gas. The advantages and design considerations of thein situcells are discussed and their usage is illustrated by a case study.

Novel solvates M(BH₄)₃S(CH₃)₂ and properties of halide-free M(BH₄)₃ (M = Y or Gd)

Rare earth metal borohydrides have been proposed as materials for solid-state hydrogen storage because of their reasonably low temperature of decomposition. New synthesis methods, which provide halide-free yttrium and gadolinium borohydride, are presented using dimethyl sulfide and new solvates as intermediates. The solvates M(BH4)3S(CH3)2 (M = Y or Gd) are transformed to α-Y(BH4)3 or Gd(BH4)3 at ~140 °C as verified by thermal analysis. The monoclinic structure of Y(BH4)3S(CH3)2, space group P2₁/c, a = 5.52621(8), b = 22.3255(3), c = 8.0626(1) Å and β = 100.408(1)°, is solved from synchrotron radiation powder X-ray diffraction data and consists of buckled layers of slightly distorted octahedrons of yttrium atoms coordinated to five borohydride groups and one dimethyl sulfide group. Significant hydrogen loss is observed from Y(BH4)3 below 300 °C and rehydrogenation at 300 °C and p(H2) = 1550 bar does not result in the reformation of Y(BH4)3, but instead yields YH3. Moreover, composites systems Y(BH4)3-LiBH4 1 : 1 and Y(BH4)3-LiCl 1 : 1 prepared from as-synthesised Y(BH4)3 are shown to melt at 190 and 220 °C, respectively.

Tailoring the properties of ammine metal borohydrides for solid-state hydrogen storage

A series of halide-free ammine manganese borohydrides, Mn(BH4 )2 ⋅nNH3 , n=1, 2, 3, and 6, a new bimetallic compound Li2 Mn(BH4 )4 ⋅6NH3 , and the first ammine metal borohydride solid solution Mg1-x Mnx (BH4 )2 ⋅6NH3 are presented. Four new crystal structures have been determined by synchrotron radiation powder X-ray diffraction and the thermal decomposition is systematically investigated for all the new compounds. The solid-gas reaction between Mn(BH4 )2 and NH3 provides Mn(BH4 )2 ⋅6NH3 . The number of NH3 per Mn has been varied by mechanochemical treatment of Mn(BH4 )2 ⋅6NH3 -Mn(BH4 )2 mixtures giving rise to increased hydrogen purity for n/m≤1 for M(BH4 )m ⋅nNH3 . The structures of Mg(BH4 )2 ⋅3NH3 and Li2 Mg(BH4 )4 ⋅6NH3 have been revisited and new structural models are presented. Finally, we demonstrate that ammonia destabilizes metal borohydrides with low electronegativity of the metal (χp <∼1.6), while metal borohydrides with high electronegativity (χp >∼1.6) are generally stabilized.

A versatile environmental control cell forin situguest exchange single-crystal diffraction

In situsingle-crystal diffraction experiments provide researchers with the opportunity to study the response of crystalline systems, including metal–organic frameworks and other nanoporous materials, to changing local microenvironments. This paper reports a new environmental control cell that is remarkably easy to use, completely reusable, and capable of delivering static or dynamic vacuum, liquids or gases to a single-crystal sample. Furthermore the device is nearly identical in size to standard single-crystal mounts so a full unrestricted range of motion is expected for most commercial goniometers.In situsingle-crystal X-ray diffraction experiments performed under dynamic gas-flow conditions revealed the cell was capable of stabilizing a novel metastable intermediate in the dehydration reaction of a previously reported metal–organic framework.

Anin situpowder diffraction cell for high-pressure hydrogenation experiments using laboratory X-ray diffractometers

Anin situdiffraction cell is presented which has been designed and constructed for in-house powder diffraction experiments under high gas pressures up to 30 MPa. For a proof of principle, thein situcell has been tested for several hydrogenation experiments under elevated pressures and temperatures. LaNi5was chosen as an example for hydrogenation, applying simultaneously 5.5 MPa H2pressure at a temperature of 423 K. For testing the high-pressure–temperature suitability of thein situcell, pressure–temperature experiments up to 14 MPa at 373 K were performed, studying the rehydrogenation of NaH and Al to NaAlH4. The experimental setup enables recording ofin situX-ray diffraction data on laboratory instruments with short data acquisition times at elevated hydrogen pressures and temperatures.

Manganese borohydride; synthesis and characterization

Three manganese borohydride polymorphs are synthesized in solution and found to be structural analogues of three magnesium borohydride polymorphs.

Exceptional adsorption-induced cluster and network deformation in the flexible metal–organic framework DUT-8(Ni) observed by in situ X-ray diffraction and EXAFS

The “gate opening” mechanism in flexible MOF Ni₂(2,6-ndc)₂dabco was elucidated in detail.