Elucidation of the Effect of Functional Group Substitution of BN-cyclohexane for Renewable Energy Hydrogen Storage: Density Functional Theory Approach

Abstract

Liquid organic hydrogen carrier (LOHC) has been attracting attention as a hydrogen storage technology. Among the LOHC materials, we explore fluorine (F) and amine (NH2) functional group substituted 1,2-BN cyclohexane-based hydrogen storage materials with improved reversibility of dehydrogenation-hydrogenation reaction. Density functional theory (DFT) calculations were conducted by using Gaussian 16 software to calculate dehydrogenation reaction enthalpy (∆) and reaction free energy (∆). F-BN-cyclohexane and NH2-BN-cyclohexane show ∆ of ‒4.10 and ‒5.38 kJ/mol, respectively, whereas 1,2-BN cyclohexane shows ∆ of ‒5.71 kJ/mol. Because the reversibility of dehydrogenation-hydrogenation reactions is excellent as the ∆ value is close to zero, the functional group substitution enhanced the reversibility of the dehydrogenation-hydrogenation reaction. This DFT study not only presents a systematic methodology to evaluate the dehydrogenation-hydrogenation reaction reversibility that can be improved by substituting F and NH2 functional groups in existing BN-cyclohexane, but also provides the fundamental mechanisms of dehydrogenation of Fand NH2-BN-cyclohexane.