Hydrogen Trapping Efficiency of Li-Decorated Metal–Carbyne\nFramework: A First-Principles Study

Abstract

The\nneed for sustainable energy fuel is much higher than before. The use\nof hydrogen as a fuel is impeded due to its low storage capacity in\nthe storage medium. In this work, a newly designed metal–carbyne\nframework (MCF) is decorated with Li atoms with an average Li binding\nenergy of 1.94 eV. Two Li atoms are used to decorate each carbyne\nlinker of the MCF. Here, using density functional theory calculations,\nwe systematically investigated the adsorption of H₂ in\nLi-decorated MCF, namely MCFLi₈. It is found that four\nH₂ molecules are adsorbed in the molecular form on each\nLi in MCFLi₈ by Niu’s charge polarization mechanism.\nOur findings revealed that the Li-decorated MCF exhibits a high hydrogen\nstorage capacity at ambient conditions with adsorption–desorption\nenergy ranging between 0.2 and 0.6 eV. Hirshfeld charge analysis and\nelectrostatic potential maps show the charge transfer mechanism during\nthe hydrogen adsorption. Born–Oppenheimer molecular dynamics\nsimulations reveal the reversibility of adsorbed hydrogen at ideal\npressure and temperature conditions. Thermodynamic usable capacity\nof adsorbed hydrogen at adsorption and desorption conditions is determined\nby calculating hydrogen occupation number. The gravimetric hydrogen\ndensity of 11.1 wt % is found for complete H₂ adsorbed\nin MCFLi₈. This study suggests that Li-decorated MCF can\nbe a promising hydrogen storage material.