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A metal-free method for H 2 -release from ammonia borane with the addition of polyethers would be helpful for the development of feasible hydrogen storage systems. As featured in:See Yongmin Kim et al., Phys. Chem. Chem. Phys., 2013, 15, 19584. 19584 Phys. Chem. Chem. Phys., 2013, 15, 19584--19594 This journal is c the Owner Societies 2013 Polyetheral additives were found to be efficient promoters to enhance the rate of H 2 -release from ammonia borane (AB) at various temperatures. In particular, tetraethylene glycol dimethyl ether (T4EGDE, 29 wt% relative to AB + T4EGDE) exhibited significantly improved activities for AB dehydrogenation, with the material-based hydrogen storage capacity of 10.3 wt% at 125 1C within 40 min. In situ FT-IR spectroscopy indicated the formation of B-(cyclodiborazanyl)amino-borohydride (BCDB), borazine, and m-aminodiborane as gaseous byproducts. In addition, 11 B nuclear magnetic resonance (NMR) spectroscopy further revealed that diammoniate of diborane (DADB) was initially formed to give polyaminoborane as liquid and/or solid spent-fuel, consistent with previous reports. Density Functional Theory (DFT) calculations suggested that hydrogen bonding interactions between ABand a polyetheral promoter initially played an important role in increasing the reactivity of B-H bonds of AB by transferring electron density from oxygen atoms of the promoter into B-H bonds of AB. These partially activated, hydridic B-H bonds were proposed to help promote the formation of diammoniate of diborane (DADB), which is considered as a reactive intermediate, eventually enhancing the rate of H 2 -release from AB. In addition, our in situ solid state 11 B magic angle spinning (MAS) NMR measurements further confirmed that the rate of DADB formation from AB with a small quantity of T4EGDE was found to be much faster than that of pristine AB even at 50 1C. This metal-free method for H 2 -release from AB with an added, small quantity of polyethers would be helpful to develop feasible hydrogen storage systems for long-term fuel cell applications.

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The susceptibility of layered structures to stacking faults is a problem in some of the more attractive semiconductor materials for ambient-temperature radiation detectors. In this work, Bridgman-grown BiI 3 layered single crystals are investigated to understand and eliminate structural disorder, which reduces radiation detector performance. The use of superheating gradients has been shown by others to improve crystal quality in non-layered semiconductor crystals [Rudolph et al., 1996]; thus the technique was explored to improve the growth of BiI 3. When investigating the homogeneity of non-superheated crystals, highly geometric void defects were found to populate the bulk of the crystals. Applying a superheating gradient to the melt prior to crystal growth improved structural quality and decreased defect density from the order of 4600 voids per cm 3 to 300 voids per cm 3. Corresponding moderate improvements to electronic properties also resulted from the superheat gradient method of crystal growth. Comparative measurements through infrared microscopy, etch-pit density, X-ray rocking curves, and sheet resistivity readings show that superheat gradients in BiI 3 growth led to higher quality crystals.

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