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

Abstract

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