2-Aminoimidazole borohydride as a hydrogen carrier

Abstract

2-Aminoimidazole borohydride (Im-NH₂BH₄) is synthesized via the reaction between 2-aminoimidazole hemisulfate ((Im-NH₂)₂SO₄) and sodium borohydride by a simple ball milling method. This compound holds theoretical hydrogen capacity of 8.1 wt%. It is designed based on the strategy of destabilizating BH₄⁻ using a large conjugated cation, Im-NH₂⁺ and maximizing the protonic-hydridic hydrogen interaction by balancing their numbers. Thermal dehydrogenation analyses demonstrate that it can release about 3.2 wt% hydrogen (Na₂SO₄ included) without gaseous impurities below 320 °C. The decomposition process has three exothermal steps and the onset dehydrogenation temperature is 50.5 °C. These results indicate that the above strategy is effective. The dehydrogenation process of this compound is discussed and the product at 320 °C is proposed to be C₃N₃H₃BH.