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Complex transition metal hydrides have been identified as being materials for multi-functional applications holding potential as thermal energy storage materials, hydrogen storage materials and optical sensors. Na2Mg2NiH6 (2Na+·2Mg2+·2H−·[NiH4]4−) is one such material. In this study, the decomposition pathway and thermodynamics have been explored for the first time, revealing that at 225 °C, hydrogen desorption commences with two major decomposition steps, with maximum H2 desorption rates at 278 and 350 °C as measured by differential scanning calorimetry. The first step of decomposition results in the formation of Mg2NiHx (x < 0.3) and NaH, before these compounds decompose into Mg2Ni and Na, respectively. PCI analysis of Na2Mg2NiH6 has determined the thermodynamics of decomposition for the first step to have a ΔHdes and ΔSdes of 83 kJ mol−1 H2 and 140 J K−1 mol−1 H2, respectively. Hydrogen cycling of the first step has been achieved for 10 cycles without any significant reduction in hydrogen capacity, with complete hydrogen desorption within 20 min at 395 °C. Despite the relatively high cost of Ni, the ability to effectively store hydrogen reversibly at operational temperatures of 318–568 °C should allow this material to be considered as a thermal energy storage material.

The Li-5(BH4)(3)NH complex hydride, obtained by ball milling LiBH4 and Li2NH in various molar ratios, has been investigated. Using X-ray powder diffraction analysis the crystalline phase has been indexed with an orthorhombic unit cell with lattice parameters a = 10.2031(3), b = 11.5005(2), and c = 7.0474(2) angstrom at 77 degrees C. The crystal structure of Lis(BH4)(3)NH has been solved in space group Pnma, and refined coupling density functional theory (DFT) and synchrotron radiation X-ray powder diffraction data have been obtained for a 3LiBH(4):2Li(2)NH ball-milled and annealed sample. Solid-state nudear magnetic resonance measurements confirmed the chemical shifts calculated by DFT from the solved structure. The DFT calculations confirmed the ionic character of this lithium-rich compound. Each Li+ cation is coordinated by three BH4- and one NH2- anion in a tetrahedral configuration. The room temperature ionic conductivity of the new orthorhombic compound is close to10(-6) S/cm at room temperature, with activation energy of 0.73 eV.

Initiation of cotton fiber from ovule epidermal cells determines the ultimate number of fibers per cotton ovule, making it one of the restriction factors of cotton fiber yield. Previous comparative proteomics studies have collectively revealed 162 important differentially accumulated proteins (DAPs) in cotton fiber-initiation process, however, whether and how post-translational modifications, especially phosphorylation modification, regulate the expression and function of the DAPs are still unclear. Here we reported the successful identification of 17 phosphopeptides from 16 phosphoproteins out of the 162 DAPs using the integrated bioinformatics analyses of peptide mass fingerprinting data and targeted MS/MS identification method. In-depth analyses indicated that 15 of the 17 phosphorylation sites were novel phosphorylation sites first identified in plants, whereas 6 of the 16 phosphoproteins were found to be the phosphorylated isoforms of 6 proteins. The phosphorylation-regulated dynamic protein network derived from this study not only expanded our understanding of the cotton fiber-initiation process, but also provided a valuable resource for future functional studies of the phosphoproteins.

An intermediate phase LaMg2NiH4.6 found for the hydrogenation reaction of the ternary intermetallic compound LaMg2Ni to the complex transition-metal hydride LaMg2NiH7 has been investigated experimentally and theoretically. It is known that this reaction induces only minor rearrangement of the host metal atoms, and this feature is also observed for the intermediate compound. Another important feature is that the electronic structure of the intermediate phase is metallic, which is free from the energy barrier associated with the metal–insulator transition. The hydrogenation reaction to the intermediate phase proceeds even at room temperature, when the Ni–H clusters are formed. The internal bonding of the Ni–H clusters has a covalent nature, the same as those of NiH4 complexes in LaMg2NiH7. They most likely play as the precursor states for the following complex hydride formation. This picture is insightful to enhance the formation of complex hydrides.

The dehydriding process and hydrogen–deuterium exchange (H–D exchange) of xLiBH4 + (1 − x)Mg2FeD6 (x = 0.25, 0.75) composites has been studied in detail. For the composition with x = 0.25, only one overlapping mass peak of all hydrogen and deuterium related species was observed in mass spectrometry. This implied the simultaneous dehydriding of LiBH4 and Mg2FeD6, despite an almost 190 °C difference in the dehydriding temperatures of the respective discrete complex hydrides. In situ infrared spectroscopy measurements indicated that H–D exchange between [BH4]− and [FeD6]4− had occurred during ball-milling and was promoted upon heating. The extent of H–D exchange was estimated from the areas of the relevant mass signals: immediately prior to the dehydriding, more than two H atoms in [BH4]− was replaced by D atoms. For x = 0.75, H–D exchange also occurred and about one to two H atoms in [BH4]− was replaced by D atoms immediately before the dehydriding. In contrast to the situation for x = 0.25, firstly LiBH4 and Mg2FeD6 dehydrided simultaneously with a special molar ratio = 1:1 at x = 0.75, and then the remaining LiBH4 reacted with the Mg and Fe derived from the dehydriding of Mg2FeD6.

Complex transition metal hydrides have potential technological application as hydrogen storage materials, smart windows and sensors. Recent exploration of these materials has revealed that the incorporation of anionic hydrogen into these systems expands the potential number of viable complexes, while varying the countercation allows for optimisation of their thermodynamic stability. In this study, the optimised synthesis of Na2Mg2TH8 (T = Fe, Ru) has been achieved and their thermal decomposition properties studied by ex situ Powder X-ray Diffraction, Gas Chromatography and Pressure-Composition Isotherm measurements. The temperature and pathway of decomposition of these isostructural compounds differs considerably, with Na2Mg2FeH8 proceeding via NaMgH3 in a three-step process, while Na2Mg2RuH8 decomposes via Mg2RuH4 in a two-step process. The first desorption maxima of Na2Mg2FeH8 occurs at ca. 400 °C, while Na2Mg2RuH8 has its first maxima at 420 °C. The enthalpy and entropy of desorption for Na2Mg2TH8 (T = Fe, Ru) has been established by PCI measurements, with the ΔHdes for Na2Mg2FeH8 being 94.5 kJ mol(-1) H2 and 125 kJ mol(-1) H2 for Na2Mg2RuH8.

In previous studies, complex hydrides LiBH4 and Mg2FeH6 have been reported to undergo simultaneous dehydrogenation when ball-milled as composite materials (1 − x)LiBH4 + xMg2FeH6. The simultaneous hydrogen release led to a decrease of the dehydrogenation temperature by as much as 150 K when compared to that of LiBH4. It also led to the modified dehydrogenation properties of Mg2FeH6. The simultaneous dehydrogenation behavior between stoichiometric ratios of LiBH4 and Mg2FeH6 is not yet understood. Therefore, in the present work, we used the molar ratio x = 0.25, 0.5, and 0.75, and studied the isothermal dehydrogenation processes via pressure–composition–isothermal (PCT) measurements. The results indicated that the same stoichiometric reaction occurred in all of these composite materials, and x = 0.5 was the molar ratio between LiBH4 and Mg2FeH6 in the reaction. Due to the optimal composition ratio, the composite material exhibited enhanced rehydrogenation and reversibility properties: the temperature and pressure of 673 K and 20 MPa of H2, respectively, for the full rehydrogenation of x = 0.5 composite, were much lower than those required for the partial rehydrogenation of LiBH4. Moreover, the x = 0.5 composite could be reversibly hydrogenated for more than four cycles without degradation of its H2 capacity.

The formation process from the intermetallic compound LaMg2Ni to a complex hydride (deuteride) LaMg2NiD7 composed of La3+, 2 × Mg2+, [NiD4]4−, and 3 × D− was investigated by in-situ powder neutron diffraction under deuterium gas pressure at room temperature. Below 0.001 MPa, small amount of deuterium was initially dissolved in the lattice of LaMg2Ni forming LaMg2NiD0.05 and two new hydride phases (LaMg2NiDx1 and LaMg2NiDx2) were continuously yielded. Furthermore, LaMg2NiD4.6 with NiD1.9 and NiD3.3 units and interstitial deuterium atoms was formed prior to appearing of LaMg2NiD7. From their Bragg peak positions, the deuterium contents x1, and x2 were inferred as 0.05

The crystal, electronic and phonon structures, and thermodynamic stability of a hypothetical complex hydride Y 2 CrH 6 were investigated using first-principles calculations. We found that the hydride contains CrH 6 octahedra in the K 2 PtCl 6 -type structure. The electronic structure illustrates that two yttrium atoms donate a total of six electrons to the octahedra, indicating the charge state Y 2 3 + [ CrH 6 ] 6 - which abides by the 18-electron rule. The phonon dispersion curves demonstrate that the hydride is dynamically stable. The calculated enthalpy change of −11 kJ/mol for the reaction, 2YH 2 +Cr + H 2 → Y 2 CrH 6 , gives a possible route to synthesize the stable complex hydride containing [CrH 6 ] 6− . The large charge state of the hexavalent complex anion [CrH 6 ] 6− would be useful to explore new complex hydrides, providing the chemical flexibility through the multiple combinations of cations.

The dehydriding property of xNaBH4 + (1 1 x) Mg2FeH6 (x = 0.1­0.75) is measured to investigate the effect of combining with complex hydride Mg2FeH6 on reducing dehydriding temperature of metal borohydrides, which has lately been found to be effective for LiBH4. When x = 0.1 and 0.125, a single-step dehydriding reaction is observed, while in the composition range x 2 0.25, a multi-step dehydriding reaction is observed. Despite the different dehydriding process, X-ray diffraction measurements confirmed that Mg2FeH6 and NaBH4 began releasing hydrogen simultaneously over the entire composition range. The results also indicate that the dehydriding temperature of NaBH4 is reduced by at least 150K when combining with Mg2FeH6. [doi:10.2320/matertrans.MG201404]

Mg(NH2)2 with three different particle sizes of 100, 500, and 2000 nm are obtained by a series of reactions between Mg, H2, and NH3. The ammonia desorption temperature decreases with the particle s...

Magnesium borohydride (Mg(BH4)2) is one of the most promising complex hydrides presently studied for energy-related applications. Many of its properties depend on the stability of the BH4(-) anion. The BH4(-) stability was investigated with respect to H→D exchange. In situ Raman measurements on high-surface-area porous Mg(BH4 )2 in 0.3 MPa D2 have shown that the isotopic exchange at appreciable rates occurs already at 373 K. This is the lowest exchange temperature observed in stable borohydrides. Gas-solid isotopic exchange follows the BH4(-) +D˙ →BH3D(-) +H˙ mechanism at least at the initial reaction steps. Ex situ deuteration of porous Mg(BH4)2 and its dense-phase polymorph indicates that the intrinsic porosity of the hydride is the key behind the high isotopic exchange rates. It implies that the solid-state H(D) diffusion is considerably slower than the gas-solid H→D exchange reaction at the surface and it is a rate-limiting steps for hydrogen desorption and absorption in Mg(BH4)2.

Cells have evolved rather sophisticated mechanisms to deal with stress positively and efficiently. Accumulation of reactive oxygen species (ROS), release of damage-associated molecular pattern molecule (DAMPs), and autophagy induction, are three inter-related processes occurring during most if not all cellular adaptations to stress. They influence each other reciprocally, initiating individual pathways, mediating and/or inducing effector mechanisms and modifying cellular function. High-mobility group box 1 (HMGB1), is a prototypic DAMP molecule, with various roles depending on its compartmental localization (nuclear, cytosolic, extracellular), well-defined but rather promiscuous binding partners, and the redox status within or without the cell. Typically, HMGB1 serves as a redox sensor, where redox modification also defines its translocation, release and activity, illustrative of the coordinate and multiply determined paths involved in the response to cell stress. Since DAMPs, redox and autophagy are essential and multifaceted in their roles in host defense, inflammation, and homeostasis, understanding how they interact and coordinate various signaling pathways to adjust to the stressful environment is important in the development of various potential therapeutic strategies, including application to patients with cancer.

Combinations of complex metal borohydrides ball milled with the transition metal complex hydride, Mg2FeH6, are analysed and compared. Initially, the Reactive Hydride Composite (RHC) of Mg2+ cation mixtures of Mg2FeH6 and γ-Mg(BH4)2 is combined in a range of molar ratios and heated to a maximum of 450 °C. For the molar ratio of 6 Mg2FeH6 + Mg(BH4)2, simultaneous desorption of the two hydrides occurred, which resulted in a single event of hydrogen release. This single step desorption occurred at temperatures between those of Mg2FeH6 and γ-Mg(BH4)2. Keeping this anionic ratio constant, the desorption behavior of four other borohydrides, Li-, Na-, K-, and Ca-borohydrides was studied by using materials ball milled with Mg2FeH6 applying the same milling parameters. The mixtures containing Mg-, Li-, and Ca-borohydrides also released hydrogen in a single event. The Mass Spectrometry (MS) results show a double step reaction within a narrow temperature range for both the Na- and K-borohydride mixtures. This phenomenon, observed for the RHC systems at the same anionic ratio with all five light metal borohydride mixtures, can be described as simultaneous hydrogen desorption within a narrow temperature range centered around 300 °C.

Formation kinetics of a complex hydride YMn2H6 with [MnH6]5− complex anion from a metal hydride YMn2H4.5 was investigated in the temperature range between 373 K and 448 K under 25 MPa H2. The time dependent of the YMn2H6 formation fraction suggested that the formation kinetics are controlled by random nucleation and growth with the activation energy of 113 kJ/mol H2. Local structure of YMn2H6 synthesized was also studied by x-ray absorption fine structure analysis. Mn–H covalent bonding nature in [MnH6]5− complex anion was successfully detected and the Mn–H distance was determined to be 1.67 ± 0.05 A.