Catalytic Effect of Ionic Liquid Induced H<sub>2</sub>-Release from Morpholine Borane Complex: An Efficient Hydrogen Storage Carrier
Dhirendra Kumar Mishra, Raghibul Hussain, G. Pugazhenthi, Tamal Banerjee
Abstract
The demand for effective and secure chemical hydrogen storage systems impedes hydrogen’s usage as an alternative energy carrier. This work reports the use of morpholine borane (MB) as a novel, efficient, and widely viable chemical hydrogen storage material for mobile applications. Herein, for the first time, hydrogen generation from the thermolytic dehydrogenation of MB in the presence of ionic liquid (IL) media is reported. Initially, the COSMO-SAC model was utilized to determine the most appropriate solvent. [Bmim][HSO4] proved to be an excellent catalytic solvent media with maximum solubility in the morpholine borane complex. Thermal dehydrogenation experiments were conducted separately on solid-state and MB-IL systems at 60 and 80 °C in a vacuum-sealed experimental setup. After a prolonged heating period, the solid-state dehydrogenation of the MB complex released 0.62 equiv of hydrogen, whereas the dehydrogenation of the MB-IL system at 60 and 80 °C released 1.75 and 1.46 equiv of hydrogen in a shorter time. The residue products were characterized using 1H and 11B nuclear magnetic resonance (NMR). 1H NMR validated IL’s activity as a catalytic solvent without affecting its structural identity, whereas 11B NMR helped establish an intra- and intermolecular dehydrogenation mechanism connected with MB. As confirmed by the density functional theory-based transition state calculations, the intramolecular dehydrogenation pathway results in a dehydrocoupled product with minimal energy required for the dehydrogenation reaction.