Tuning the dehydrogenation performance of dibenzyl toluene as liquid organic hydrogen carriers

Abstract

Strategies to decrease the dehydrogenation enthalpy (ΔHd) of dibenzyl toluene (DBT) were examined by density functional theory (DFT) modeling. The stronger electron-donating substituent showed higher hydrogen-releasing properties. The sequences of the dehydrogenation process of perhydro-dibenzyl toluene (18H-DBT) and perhydro-lithium 3,5-dibenzyl phenolate (18H-DBT-OLi), which is the compound of modified DBT with the highest potential, were the same. The energy required to release hydrogen from 18H-DBT-OLi (11.514 kcal/mol) was smaller than that from 18H-DBT (12.574 kcal/mol). In the hydrogen-releasing process, the rate-determining steps for the dehydrogenation of 18H-DBT and 18H-DBT-OLi were the 12H-DBT → 10H-DBT + H2 and 12H-DBT-OLi → 10H-DBT-OLi + H2 steps, respectively. Furthermore, the charge distribution of 18H-DBT and 18H-DBT-OLi was also explored.