(622b) Promoted Effect of D-Mannitol on Thermal Dehydrogenation of Ammonia Borane

Increasing CO₂ emissions from burning fossil fuels put tremendous pressure on the ecosystem cycle. In this context, hydrogen is a clean energy carrier that produces water, heat, and electricity when consumed in fuel cells. Among the chemical hydrides, ammonia borane (AB, NH₃BH₃) has attracted a great deal of attention as a promising hydrogen storage candidate, owing to its high hydrogen content (19.6%), decomposition under the moderate condition, and stability at room temperature. However, relatively high operating temperature, long-induction period, low H₂ yield, and slow kinetics remain challenges for thermal dehydrogenation of AB. In the present work, d-mannitol was employed as an additive to promote AB dehydrogenation. The effect of d-mannitol was investigated over a wide range of AB weight ratio, pressure, temperature, density, and heating rate. It was found that hydrogen yield and thermal characteristics were influenced by these operating parameters. Furthemore, the hydrogen release kinetics for AB dehydrogenation is significantly enhanced by addition of d-mannitol. Along with rapid kinetics, the high hydrogen equivalent (> 2) was obtained at 1 atm and 85 ^oC, near PEM fuel cell operating temperatures. Finally, TPD/MS and ¹¹B MAS NMR analysis were performed to understand reaction mechanisms. The results show that our proposed method is promising for hydrogen storage and can be used in various applications equipped with PEM fuel cell.