BN-bicyclohexyl material for enhanced reversible dehydrogenation reaction for hydrogen storage: Density functional theory approach

Abstract

Hydrogen is considered as an environmentally friendly energy resource to replace fossil fuels. This study aims to enhance the dehydrogenation efficiency of liquid organic hydrogen carrier (LOHC) materials by investigating the dehydrogenation and hydrogenation mechanisms through hetero atom (B and N) substitution of bicyclohexyl, as well as by applying the high-efficiency catalysts, palladium and ruthenium. To achieve this, BN-bicyclohexyl, a novel material based on bicyclohexyl, was proposed using density functional theory (DFT) calculations, and the synthesis of the new material was evaluated through enthalpy and free energy calculations. Mulliken charge analysis showed that the B and N atoms substituted in bicyclohexyl can induce dihydrogen bonding, resulting in efficient dehydrogenation at the substitution site. The dehydrogenation efficiency of BN-bicyclohexyl (1.53 eV in activation energy) surpasses that of bicyclohexyl (2.77 eV) on the Pd(111) surface. However, on the Ru(001) surface, BN-bicyclohexyl exhibits a slightly lower hydrogenation efficiency than bicyclohexyl, with an increase of 0.39 eV in activation energy. This trend highlights BN as a promising candidate for enhancing the capability of LOHCs. Notably, the dehydrogenation efficiency of BN-bicyclohexyl is significantly higher than that of bicyclohexyl, which go beyond slightly lower hydrogenation efficiency than bicyclohexyl.