Dehydrogenation of ammonia borane recrystallized by different techniques

The literature shows that practically no attention has been paid to the size and shape of the particles of bulk ammonia borane (NH3BH3). The published results about the influence of the dispersity of this hydride on its dehydrogenation are not numerous and contradictory. This work presents new results on the low-temperature solid-state dehydrogenation of bulk NH3BH3. The samples under study were recrystallized using different procedures and had, therefore, different particle characteristics. The reactivity of these samples of NH3BH3 was compared on the basis of thermal analysis data obtained under non-isothermal conditions, including the Kissinger kinetics, and H-2 evolution under isothermal conditions (84-96 & DEG;C) using Avrami-Erofeev kinetics. The finely dispersed sample with a particle size of < 40 mm was found to be the most active one. A correlation between the NH3BH3 melting temperature and the temperature of its dehydrogenation has been established. A filamentous NH3BH3 with a length to-thickness ratio of the filaments of > 100 was synthesized and described for the first time. It was suggested that its relatively high reactivity was determined by its ordered structure. These results show the importance of further investigations of bulk ammonia borane with different types of particles.& nbsp;(c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The particle size and shape of bulk ammonia borane (NH3BH3) have received little attention in the literature. The published results on the influence of hydride dispersity on its dehydrogenation are limited and contradictory. This study presents new findings on the solid-state dehydrogenation of NH3BH3 at low temperatures. Samples with different particle characteristics, obtained by recrystallization using different procedures, were compared based on thermal analysis data and hydrogen evolution experiments. The results showed that the finely dispersed sample with a particle size of < 40μm exhibited the highest reactivity. A filamentous NH3BH3 with an ordered structure was synthesized and found to have relatively high reactivity. These findings highlight the need for further investigations on bulk ammonia borane with different particle types.