- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
Using the first-principles density functional theory approach, a detailed gas phase dehydrogenation analysis has been carried out for the monomeric as well as the dimeric units of lithium hydrazinidoborane (LiN2H3BH3). Atoms in molecules formalism (AIM) has been employed in order to get bonding features along the desired reaction pathways. The exploration of potential energy surfaces from different structural isomers of both monomeric and dimeric hydrazinidoborane (LiHB) suggests that all the dehydrogenation reactions are endothermic in nature. Hydrogen generation from the dimeric lithium hydrazinidoborane provides an idea about the effect of neighbouring molecules on the dehydrogenation process occurring in the solid state. The lithium ion plays the central role in transferring the hydride in the dehydrogenation of both the monomeric and dimeric form of hydrazinidoborane. In summary our theoretical calculations are expected to shed light on the decomposition mechanism of alkali metal substituted hydrazine-borane type of compounds.
Due to the coexistence of protic and hydridic hydrogen atoms in the same molecule, compounds having B and N entities have drawn much attention towards chemical hydrogen storage. The simplest amine-borane i.e. NH3BH3 (AB) provides 19.6 wt% of hydrogen storage and is proved to be one of the high-capacity solid-state based chemical hydrogen storage materials (HSM) [1,2]. Among the various approaches undertaken, modification of the chemical environment of AB through the replacement of one of its H by strongly electropositive metals (Li, Na, K) has been studied widely in order to get improved dehydrogenation properties of AB [3e17].
In this work, we have systematically explored and analysed the potential energy surfaces for the decomposition of monomeric and dimeric lithium hydrazinidoborane. The three isomers of LiHB are found to be energetically close to each other and all of them undergo dehydrogenation processes which are subsequently characterized from a thermodynamic point of view. Among all the decomposition pathways from monomeric LiHB, NH3 release channel, originating from R1 isomer, is found to be highly exothermic in nature. Comparison of the hydrogen elimination from all of these three isomers of LiHB shows that most of the dehydrogenation steps are energetically unfavourable due to the high energy barriers associated with them. In case of monomeric dehydrogenation channels, hydrogen generation is only found to be possible from the lower energy decomposition channel originated from R2 isomer (pathway 1).