Defying Thermodynamics: Stabilization of Alane Within Covalent Triazine Frameworks for Reversible Hydrogen Storage.

The highly unfavorable thermodynamics of direct aluminum hydrogenation can be overcome by stabilizing alane within a nanoporous bipyridine-functionalized covalent triazine framework (AlH @CTF-bipyridine). This material and the counterpart AlH @CTF-biphenyl rapidly desorb H between 95 and 154 °C, with desorption complete at 250 °C. Sieverts measurements, Al MAS NMR and Al{ H} REDOR experiments, and computational spectroscopy reveal that AlH @CTF-bipyridine dehydrogenation is reversible at 60 °C under 700 bar hydrogen, >10 times lower pressure than that required to hydrogenate bulk aluminum.

Cationically Substituted BiFeOCl Nanosheets as Li Ion Battery Anodes.

Cation substitution of Bi with Fe in BiOCl leads to the formation of ionically layered BiFeOCl nanosheets. The synthesis follows a hydrolysis route using bismuth(III) nitrate and iron(III) chloride, followed by postannealing at 500 °C. Room temperature electrical conductivity improves from 6.

First-principles calculated decomposition pathways for LiBH4 nanoclusters.

We analyze thermodynamic stability and decomposition pathways of LiBH4 nanoclusters using grand-canonical free-energy minimization based on total energies and vibrational frequencies obtained from density-functional theory (DFT) calculations. We consider (LiBH4)n nanoclusters with n = 2 to 12 as reactants, while the possible products include (Li)n, (B)n, (LiB)n, (LiH)n, and Li2BnHn; off-stoichiometric LinBnHm (m ≤ 4n) clusters were considered for n = 2, 3, and 6. Cluster ground-state configurations have been predicted using prototype electrostatic ground-state (PEGS) and genetic algorithm (GA) based structural optimizations.

Reversible hydrogen storage by NaAlH4 confined within a titanium-functionalized MOF-74(Mg) nanoreactor.

We demonstrate that NaAlH(4) confined within the nanopores of a titanium-functionalized metal-organic framework (MOF) template MOF-74(Mg) can reversibly store hydrogen with minimal loss of capacity. Hydride-infiltrated samples were synthesized by melt infiltration, achieving loadings up to 21 wt %. MOF-74(Mg) possesses one-dimensional, 12 Å channels lined with Mg atoms having open coordination sites, which can serve as sites for Ti catalyst stabilization.

Density functional theory studies on the electronic, structural, phonon dynamical and thermo-stability properties of bicarbonates MHCO(3), M = Li, Na, K.

The structural, electronic, phonon dispersion and thermodynamic properties of MHCO(3) (M = Li, Na, K) solids were investigated using density functional theory. The calculated bulk properties for both their ambient and the high-pressure phases are in good agreement with available experimental measurements. Solid phase LiHCO(3) has not yet been observed experimentally.

Tuning metal hydride thermodynamics via size and composition: Li-H, Mg-H, Al-H, and Mg-Al-H nanoclusters for hydrogen storage.

Nanoscale Li and intermetallic Al-Mg metal hydride clusters are investigated as a possible hydrogen storage material using the high-level quantum Monte Carlo computational method. Lower level methods such as density functional theory are qualitatively, not quantitatively accurate for the calculation of the enthalpy of absorption of H(2). At sizes around 1 nm, it is predicted that Al/Mg alloyed nanoparticles are stable relative to the pure compositions and the metal composition can be tuned in tandem with the size to tune the hydrogen absorption energy, making this a promising route to a rechargeable hydrogen storage material.

Improved synthesis of bis(borano)hypophosphite salts.

A synthesis of the bis(borano)hypophosphite anion with various counterions has been developed to make use of more benign and commercially available reagents. This method avoids the use of potentially dangerous reagents used by previous methods and gives the final products in good yield. Details of the crystal structure determination of the sodium salt in space group Ama2 are given using a novel computational technique combined with Rietveld refinement.

Calcium borohydride for hydrogen storage: catalysis and reversibility.

We demonstrate a new solid-state synthesis route to prepare calcium borohydride, Ca(BH4)2, by reacting a ball-milled mixture of CaB(6) and CaH(2) in a molar ratio of 1:2 at 700 bar of H2 pressure and 400-440 degrees C. Moreover, doping with catalysts was found to be crucial to enhance reaction kinetics. Thermogravimetric analysis and differential scanning calorimetry revealed a reversible low-temperature to high-temperature endothermic phase transition at 140 degrees C and another endothermic phase transition at 350-390 degrees C associated with hydrogen release upon formation of CaB(6) and CaH(2), as was evident from X-ray diffraction analysis.

Crystal structure, Raman spectroscopy, and ab initio calculations of a new bialkali alanate K2LiAlH6.

A new bialkali alanate K2LiAlH6 was synthesized at 320-330 degrees C and 100-700 bar. It was structurally characterized by powder X-ray diffraction. It crystallizes in space group R3m (No.