This paper reports on the synthesis of ammonia borane (NH₃BH₃, AB) from sodium borohydride and ammonia complex Ni(NH₃)₆•Cl₂ and the dehydrogenation of the as-synthesized AB. The composition and purity of the products have been tested by instrumental analyses of XRD, FTIR, ¹¹B NMR and ICP. The effects of raw materials molar ratio, reaction temperature, reaction time and solvent on the synthesis of AB have been systematically investigated. At the same time, a thermal decomposition process has also been explored on the as-prepared AB with different raw material ratios. The results show that a pure phase AB (purity＞99%) can be obtained with the molar ratio of NaBH₄∶Ni(NH₃)₆Cl₂＝2∶1 and the reaction time of 10 h. Thermal analysis displays that the hydrogen gas is released in the first step from AB with raw material molar ratio of NaBH₄∶Ni(NH₃)₆Cl₂＝3∶1, and impurities of diborane (m/e＝27), borazine (m/e＝80) are effectively inhibited at the heating rate of 2 ℃/min. In addition, a certain amount of Ni nanoparticles with the size of about 10 nm exist in the products, which would be used as a catalyst for the hydrolysis of AB.

Key words: ammonia borane (AB), preparation, thermal decomposition, catalyst