Abstract
Ammonia borane NH3BH3 (AB), a remarkable hydrogen storage material carrying 19.6 wt% of hydrogen, owns attractive properties. It (in thermolytic conditions) has been understandably much investigated within the past two decades leading to destabilization strategies in order to decrease the onset dehydrogenation temperature (<100°C). Nanosizing AB is an attractive approach to make it suitable for solid-state hydrogen storage. The destabilization of the borane (i.e. modified thermal stability and reactivity) has been anticipated via changed atomic charges of the NH3BH3 molecule, perturbed intermolecular N−H‧‧‧H−B network and lowered activation energy. The nanoconfinement of AB has then shown new pathway to dehydrogenation properties. With this knowledge, it was demonstrated that different porous structures so called scaffolds can be used to improve dehydrogenation properties of AB, such as silica (ex. SBA-15), MOF (ex. Mg-MOF-74) or polymers (ex. PMMA). In regards to efficiency, sustainability and disruption, AB has been nanosized without scaffold. Inspired from the nanosized AB using cetyltrimethylammonium bromide (CTAB) as surfactant, and obtained via an anti-precipitation method in solution, we used amine-borane adducts to produce nanosized AB particles (60 to 200nm). Adducts are the keys for shaping. Different adducts R-NH2-BH3 with R a carbonaceous group have been successfully synthesized and characterized. We have produced adducts such as tetradecylamineborane (C16H33NH2BH3AB) and biphenylamineborane (C12H11NH2BH3). The self-assembling properties of adducts have allowed nanostructuring of AB in solution; spherical, lamellar and polyhedral shapes have been observed. We accordingly synthesized nanoparticles of AB without a scaffold, which opens new perspectives for elaborating from these nanostructured new C-doped B-N-based materials. Recent computational works support that such materials would be the most attractive solutions for reversible H2 storage at ambient conditions. However, there is to our knowledge a lack of experimental evidence yet. The present project aims at confirming the potential of high reversible H2 storage in the field of B-based ceramics.