Volume 5: Innovative Solutions for Energy Transitions: Part IV

Theoretical Study on the Pyrolytic Dehydrogenation Mechanism of Ammonia Borane Xiao Tan, Libin Shi, Jiawei Yan, Suitao Qi

Abstract

Due to the increasing consumption of traditional fossil energy sources and the resulting environmental problems, the need for new energy sources is increasing. Hydrogen is an efficient and clean energy, and developing a suitable hydrogen storage medium is the key to the use of hydrogen energy. Ammonia borane has attracted much attention due to its high hydrogen storage density (19.6 wt %) and room temperature stability. It can be dehydrogenated by hydrolysis and pyrolysis. At present, the pyrolytic dehydrogenation mechanism of ammonia borane is still unclear. In this work, the dehydrogenation of ammonia borane (AB), ammonia borane dimer ((AB)2), and the diaminodiborane (DADB) have been studied based on density functional theory (DFT). The results show that the energy barriers of the first and second steps for AB pyrolytic dehydrogenation are 38.58 kcal/mol and 78.14 kcal/mol. (AB)2 dehydrogenation were generated by forming N-H…H-B bond, the energy barriers for the first step (46.45 kcal/mol) is higher than AB. In addition, the energy barrier (21.67 kcal/mol) of DADB to form N-H…H-B bond dehydrogenation is much smaller than (AB)2. It reveals that DADB is easier to dehydrogenate than AB and (AB)2. The above results would provide theoretical guidance for the pyrolytic dehydrogenation of ammonia borane.

Keywords ammonia borane, density functional theory (DFT), pyrolysis dehydrogenation, reaction mechanism