Promoted hydrogen release from ammonia borane with mannitolvia a solid-state reaction route

Abstract

Promoted hydrogen release from ammonia borane (NH₃BH₃, AB) with mannitol (C₆H₈(OH)₆, MA) additive is reported. It is found that for the MA/2AB sample, the dehydrogenation temperature is lowered by ∼25 °C compared to that of neat AB, the liberation of undesired byproduct borazine is suppressed, and the released ammonia can be removed by using anhydrous MgCl₂ as absorber. The analyses of Raman, Fourier transform infrared spectroscopy and ¹¹B nuclear magnetic resonance spectroscopy demonstrate the breaking of B–N, B–H and O–H bonds and the formation of B–O bonds for the dehydrogenation process of MA/2AB. These results suggest a solid-state dehydrogenation reaction between AB and MA: the B–H^δ− bonds in AB and the O–H^δ+ bonds in MA combine with each other to release H₂. Furthermore, the use of the perfect –OH carrier MA as additive leads to a straightforward understanding of the improved dehydrogenation of AB under the effect of hydroxyl groups in the solid state.