•Two new amide chloride phases have been identified with reduced chloride content.•Both Li7(NH2)6Cl and Li6Mg0.5(NH2)6Cl released H2, but not NH3, on reaction with LiH.•In both cases the temperature of hydrogen release was lower than observed for LiNH2.•Hydrogen release was found to be reversible for both new compounds.•The imide products were more easily rehydrogenated than those of Li4(NH2)3Cl.Two new amide chloride phases, with approximate stoichiometries Li7(NH2)6Cl and Li6Mg0.5(NH2)6Cl, have been identified by powder X-ray diffraction, and their hydrogen storage properties studied. Both phases released hydrogen on reaction with LiH at a lower temperature than observed for lithium amide, and ammonia release was suppressed. The chloride ions were maintained within the structure after hydrogen desorption and rehydrogenation, raising the possibility that the materials might be cycled. The desorption properties of Li7(NH2)6Cl were found to be similar to the previously reported amide chloride Li4(NH2)3Cl but with a much reduced gravimetric penalty owing to chloride incorporation. Rehydrogenation of the imide products of reaction of both Li7(NH2)6Cl and Li6Mg0.5(NH2)6Cl with LiH occurred more readily at 90 bar and 300 °C than that of Li4(NH2)3Cl.

•H2 desorption from 2LiNH2–MgH2–xCaX2 (x = 0, 0.1, 0.15; X = Cl, Br) samples studied.•Addition of calcium halides reduced the desorption temperature in all samples.•Peak H2 release was around 150 °C lower in ball-milled than in hand-ground samples.•The 2LiNH2–MgH2–0.15CaBr2 sample showed the lowest peak desorption temperature.•CaBr2 reduced the activation energy to 78.8 kJ mol−1, 24% less than the undoped sample.Calcium-halide-doped lithium amide–magnesium hydride samples were prepared both by hand-grinding and ball-milling 2LiNH2–MgH2–xCaX2 (x = 0, 0.1, and 0.15; X = Cl or Br). The addition of calcium halides reduced the hydrogen desorption temperature in all samples. The ball-milled undoped sample (2LiNH2–MgH2) began to desorb hydrogen at around 125 °C and peaked at 170 °C. Hydrogen desorption from the 0.15 mol CaCl2-containing sample began ca 30 °C lower than that of the undoped sample and peaked at 150 °C. Both the onset and peak temperatures of the CaBr2 sample (x = 0.15) were reduced by 15 °C compared to the chloride. Kissinger’s method was used to calculate the effective activation energy (Ea) for the systems: Ea for the 0.15 mol CaCl2-containing sample was found to be 91.8 kJ mol−1 and the value for the 0.15 mol CaBr2-containing sample was 78.8 kJ mol−1.

•Reactions of ZnCl2 + nLiNH2 gave a mixture of Zn3N2 and LiZnN as products.•No stable amide chloride, imide chloride or nitride chloride phases were identified.•The addition of lithium hydride (LiH) changed the main gaseous product from NH3 to H2.•Neither pure LiZnN nor Zn3N2 could be rehydrogenated under the conditions studied.•LiZnN/Zn3N2, and LiZnN/LiCl mixtures hydrogenated at 300 °C to form LiNH2 and Zn metal.Reactions of ZnCl2 + nLiNH2 at a range of molar ratios and temperatures gave a mixture of Zn3N2 and LiZnN as products; no stable amide chloride, imide chloride or nitride chloride phases were identified. Temperature-programmed desorption with mass spectrometry (TPD–MS) showed that the main gas emitted was ammonia (NH3). The addition of lithium hydride (LiH) changed the main gaseous product from NH3 to H2, which was released at a low temperature beginning around 90 °C. Neither pure LiZnN nor Zn3N2 could be rehydrogenated under the conditions studied. However, mixtures of LiZnN and Zn3N2, and LiZnN and LiCl reacted with H2 at 300 °C to form LiNH2 and zinc metal.

•The lower limits of halide incorporation in lithium amide have been investigated.•The only amide iodide stoichiometry observed was Li3(NH2)2I.•Solid solutions were observed in both the amide chloride and amide bromide systems.•A 46% reduction in chloride content resulted in a new phase: Li7(NH2)6Cl.•New low-chloride phase maintained improved H2 desorption properties of Li4(NH2)3Cl.An investigation has been carried out into the lower limits of halide incorporation in lithium amide (LiNH2). It was found that the lithium amide iodide Li3(NH2)2I was unable to accommodate any variation in stoichiometry. In contrast, some variation in stoichiometry was accommodated in Li7(NH2)6Br, as shown by a decrease in unit cell volume when the bromide content was reduced. The amide chloride Li4(NH2)3Cl was found to adopt either a rhombohedral or a cubic structure depending on the reaction conditions. Reduction in chloride content generally resulted in a mixture of phases, but a new rhombohedral phase with the stoichiometry Li7(NH2)6Cl was observed. In comparison to LiNH2, this new low-chloride phase exhibited similar improved hydrogen desorption properties as Li4(NH2)3Cl but with a much reduced weight penalty through addition of chloride. Attempts to dope lithium amide with fluoride ions have so far proved unsuccessful.

•Li6NBr3 was synthesized via solid state methods and hydrogenation attempted.•Hydrogenation of a lithium nitride halide was demonstrated for the first time.•Powder XRD and Raman spectroscopy showed that hydrogenation had gone to completion.•The ionic conductivities of Li6NBr3 and Li3N were compared through A.C. impedance spectroscopy.•The lower conductivity of Li6NBr3 is consistent with its higher hydrogenation temperature.The reaction of lithium amide and imide with lithium halides to form new amide halide or imide halide phases has led to improved hydrogen desorption and absorption properties and, for the amides, lithium ion conductivities. Here we investigate the effect of bromide incorporation on the ionic conductivity and hydrogen absorption properties of lithium nitride. For the first time we show that it is possible for a lithium halide nitride, the cubic bromide nitride Li6NBr3, to take up hydrogen—a necessary condition for potential use as a reversible solid-state hydrogen storage material. Powder X-ray diffraction showed the formation of Li2Br(NH2) and LiBr, and Raman spectroscopy confirmed that only amide anions were present and that the hydrogen uptake reaction had gone to completion. The lithium ion conductivity of Li6NBr3 at the hydrogenation temperature was found to be less than that of Li3N, which may be a significant factor in the kinetics of the hydrogenation process.

Variable-temperature powder X-ray diffraction studies have been used to monitor dramatic changes in the thermal expansion properties of zeolites with the LTA topology on changing the pore contents. Detailed structural analysis was performed on dehydrated Li-, Na-, K-, Rb-, and Cs-exchanged zeolite A and a comparison made with their purely siliceous analogue ITQ-29. Mean thermal expansion coefficients were also determined for the hydrated alkali-metal-exchanged forms. Thermal expansion behavior ranging from negative to positive was observed as different monovalent cations were included in the zeolite pores. Cation-induced strain to the zeolite framework has been shown to play a significant role in the thermal expansion mechanism of LTA-zeolites. Atomic-scale mechanisms behind the thermal expansion behavior have been deduced for ITQ-29, dehydrated Ag-A, and dehydrated Na-A systems.

X-Ray powder diffraction studies have been used to measure the thermal expansion properties of three zeolites with the LTA topology and provide details of the underlying structural changes. Siliceous ITQ-29 and dehydrated and hydrated silver zeolite A have large negative, moderate negative and positive thermal expansion coefficients, respectively.

Copper(I) chloride nanowires have been synthesized by heating the salt in the presence of copper zeolite X (FAU structure type). Their structure and composition were studied by powder X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. Wire growth was found to be dependent on a number of factors, the most important being the temperature of the reaction. The mechanism of wire growth, involving the occlusion of CuCl within the zeolite pores, is discussed.

The structure of the new complex hydride Li2BH4NH2, determined through Rietveld analysis of synchrotron X-ray and neutron powder diffraction data, comprises a hexagonal array of discrete (LiNH2)6 clusters dispersed in a LiBH4 matrix.

The reactions xLiNH2 + (1 − x)LiBH4 and xNaNH2 + (1 − x)NaBH4 have been investigated and new phases identified. The lithium amide–borohydride system is dominated by a body centred cubic compound of formula Li4BH4(NH2)3. In the sodium system, a new hydride of approximate composition Na2BH4NH2 has been identified with a primitive cubic structure and lattice parameter a ≈ 4.7 Å. The desorption of gases from the two amide–borohydrides on heating followed a similar pattern with the relative proportions of H2 and NH3 released depending critically on the experimental set-up: in the IGA, ammonia release occurred in two steps – beginning at 60 and 260 °C for Li4BH4(NH2)3 – the second of which was accompanied by hydrogen release; in the TPD system the main desorption product was hydrogen—again at 260 °C for Li4BH4(NH2)3 accompanied by around 5% ammonia. We hypothesize that the BH4− anion can play a similar role to LiH in the LiNH2 + LiH system, where ammonia release is suppressed in favour of hydrogen. The reaction xLiNH2 + (1 − x)LiAlH4 did not result in the production of any new phases but TPD experiments show that hydrogen is released from the mixture 2LiNH2 + LiAlH4, over a wide temperature range. We conclude that mixed complex hydrides may provide a means of tuning the dehydrogenation and rehydrogenation reactions to make viable storage systems.

Rietveld analysis of synchrotron powder X-ray diffraction data obtained from the product of the reaction of cadmium vapour with dehydrated zinc-exchanged zeolite A (LTA structure type) indicates the formation of cationic zinc–cadmium alloy clusters. The clusters are located in approximately 40% of the sodalite cages; the remaining 60% of the cages contain divalent zinc ions coordinated both to the oxygen atoms of the zeolite framework and to residual extra framework oxygen.

The solid solution, (LiNH2)x(LiBH4)(1−x), formed through the reaction of the two potential hydrogen storage materials, LiNH2 and LiBH4, is dominated by a compound that has an ideal stoichiometry of Li4BN3H10 and forms a body-centred cubic structure with a lattice constant of ca. 10.66 Å.

We report the results of a detailed examination of the occlusion of silver nitrate in silver zeolite A (AgA). The superlattice reported to occur in (AgNO3)9–AgA was found to melt at between 80 and 100 °C on heating and reappear when the sample was cooled down to 80 °C. Annealing in this temperature range and rigorous exclusion of water produced an enhancement of the superlattice peaks, which results from ordering of the contents of the zeolite cages. Peaks assigned to the superlattice were indexed with the tetragonal lattice parameters a = 17.440(5) and c = 12.398(4) Å and proposed space group P4/nmm. The sharp peaks representing the lattice of the framework (a = 12.3711(5) Å, Pmm) remained largely unaffected by the guest in this compound, which was found to exhibit strong negative thermal expansion. The host and guest lattices are incommensurate with the tetragonal guest lattice being slightly larger than the cubic host in the c-direction and slightly smaller in the a- and b-directions.

We report the discovery of a new, chemical route for ‘activating’ the hydrogen store MgH2, that results in highly effective hydrogen uptake/release characteristics, comparable to those obtained from mechanically-milled material.

Temperature dependent powder X-ray diffraction studies of zinc-exchanged zeolite A (LTA structure type; cubic at room temperature) have demonstrated the presence of a non-cubic phase between 150 °C and 600 °C. Analysis of the data indicated that a rhombohedral phase was formed with refined lattice parameters a = 17.182(3) Å and α = 59.147(9)° (after quenching from 150 °C to room temperature under vacuum). Heating above 600 °C produced a second cubic phase, which persisted upon cooling, and the rhombohedral phase only appeared for samples that had not been heated above 600 °C. The distortion from cubic symmetry may be linked to the formation of species such as Znx(H2O)ym+ or Znx(H2O)y(OH)zn+ during dehydration.

Large crystallites of high purity zeolite rho were synthesized by controlled monitoring of the aging and heating period of the mother gel. The microwave conductivity of Rb-rho doped with up to 20 Rb atoms per unit cell was measured over the temperature range 15–300 K, and the structures of three of the samples were examined through Rietveld analysis of powder neutron diffraction data. At low concentrations of rubidium dopant the observed microwave responses were dominated by polarization effects. In the sample Rb17/Rb-rho a strongly temperature-dependent electronic contribution to the conductivity was observed above ≈150 K. In Rb20/Rb-rho, conductivities in the range 1.5–2.3 Sm−1 were observed between 15 and 300 K. This residual conductivity at 15 K, unprecedented in a zeolite, indicates that the sample is indeed metallic; however, the values of conductivity measured are low in comparison to conventional metals and comparable to those of doped semiconductors. The evolution of the conducting behaviour is discussed in relation both to observed structural and to possible electronic changes occurring within the samples on metal doping.

Silver nanowires both included in and extruded from a purely siliceous mesoporous support have been produced from silver ion containing precursors prepared through dry salt occlusion.

We report the synthesis and structure, obtained through Rietveld analysis of powder synchrotron X-ray diffraction data, of zinc oxide clusters encapsulated in zeolite LTA.

We report the application of 27Al and 29Si MAS NMR to provide a direct probe of alkali metal cluster formation and distribution in the α-cages of zeolite A (LTA).

X-Ray powder diffraction studies have been used to measure the thermal expansion properties of three zeolites with the LTA topology and provide details of the underlying structural changes. Siliceous ITQ-29 and dehydrated and hydrated silver zeolite A have large negative, moderate negative and positive thermal expansion coefficients, respectively.

The structure of the new complex hydride Li2BH4NH2, determined through Rietveld analysis of synchrotron X-ray and neutron powder diffraction data, comprises a hexagonal array of discrete (LiNH2)6 clusters dispersed in a LiBH4 matrix.