Ammonia borane Borazane (NH3BH3) also called borazane ammonia borane has been considered, since its synthesis in 1955, a promising compound for hydrogen storage due to its remarkably high hydrogen content (19.6 wt%) and volumetric density (146 g(H2) 1-1); moreover it is non-toxic and stable at ambient temperature. A large amount of scientific literature has, therefore, been produced on ammonia borane dehydrogenation processes. Hydrogen can be produced by hydrolysis or thermolysis of ammonia borane. In the present chapter we focus our attention on thermal decomposition of ammonia borane. Some hints are also given about ammonia borane synthesis and regeneration. Upon Heating heatingammonia borane, a structural modification occurs in ammonia borane at about 70°C before hydrogen evolution. About 2 moles of hydrogen per mole of ammonia borane (15 wt%) are thermally released in the 110-150 °C temperature range through a two-steps exothermic reaction. However, the decomposition rate is extremely low (several hours). Complete decomposition of ammonia borane takes place at temperatures above 500°C. The decomposition reaction steps have been extensively studied by complementary experimental techniques: differential scanning calorimetry (DSC), thermogravimetric analyses (TGA) and differential thermo-analysis (DTA) at various temperature scan rates followed by isothermal desorption, thermogravimetric analyses (TGA), volumetric and spectroscopic methods. The study of thermodynamic and of the structural and thermodynamic modifications occurring at each step and the identification of the corresponding reaction products allowed a detailed description of the involved chemical reactions. Doping and or dispersing ammonia borane into nanostructures have showned beneficial effects on hydrogen ammonia borane desorption rate. Ammonia borane metal composites have also been investigated as high capacity hydrogen storage materials. Some hints are also given about ammonia borane synthesis and regeneration. © 2011 by Nova Science Publishers, Inc. All rights reserved.
|Title of host publication||Boron Hydrides, High Potential Hydrogen Storage Materials|
|Publisher||Nova Science Publishers, Inc.|
|Publication status||Published - 2011|
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