This article presents the hydrogen storage capacity of Ar encapsulated and Li functionalized Si 12 C 12 heterofullerene using state-ofthe-art Density Functional Theory (DFT) simulations. We find that the Li atom regioselectively prefers to bind at the top of the tetragonal sites of Ar encapsulated Si 12 C 12 heterofullerene with a maximum binding energy of 2.02 eV. Our study reveals that inert gas Ar encapsulation inside bare Si 12 C 12 provides greater stability to the heterofullerene by reducing the distortion. Hence, it provides a steady platform for Li decoration and successive H 2 adsorption. The adsorption energies of sequentially hydrogen
Summary
This article addresses the reversible hydrogen storage capacities of lithium (Li) decorated and silicon (Si) substituted normalC20 fullerene using density functional theory. The stabilities of the newly designed Si2normalC18Li6 and Si4normalC16Li6 cages have been verified from their chemical hardnesses and HOMO−LUMO gaps. The interaction between normalH2 molecules and the Li centers occurs via a Niu‐Rao‐Jena type interaction. Topological analysis reveals that the nature of the bonding between normalH2 and the host clusters as a weak non‐covalent type. The normalH2 molecules in Si2C18Li6‐nH2 and Si4C16Li6‐nH2 are found to be adsorbed in quasi‐molecular fashion with the average adsorption energies in the range of 0.119 eV ‐ 0.139 eV and 0.131 eV ‐ 0.140 eV, respectively. The molecular dynamics simulation confirms the thermal stability and structural integrity of Li decorated Si2normalC18 and Si4normalC16 cages at a relatively high temperature of 400 K. It has been observed that between 300 K and 400 K, most of the hydrogen molecules get desorbed from the host cages, and the structures of the clusters remain almost intact after the complete desorption, which confirmed their reversibility. The practical storage capacities of Si2normalC18Li6 and Si4normalC16Li6 cages at temperature and pressure ranges of 40 K ‐ 140 K, 40 K ‐ 120 K, and 1 ‐ 60 bar are found to be 16.09 % and 14.77 wt%, which are fairly high as compared to the target of the United States Department of Energy (5.5 wt% by 2020). Moreover, we have found that at the temperature and pressure of 200 K and 40 bar, the gravimetric density of both the cages are approximately 5.5 wt%. Hence, the newly designed Si2normalC18Li6 and Si4normalC16Li6 cages can be considered as promising materials for hydrogen storage systems.
Industrial revolution and sustainable development have intensified the need for clean resources of energy. Among all the possible alternative sources of green energy, hydrogen energy is the most promising one because of its abundancy, maximum energy density per unit mass, and clean combustion. The energy content per unit mass of hydrogen is estimated to be the highest among all known chemical fuels. Therefore, it has enough potential to meet the rising energy demand if some major barriers in its production, storage, and effective commercial or vehicular use are resolved efficiently. One of the most significant challenges in the development of a global hydrogen-based economy is the hydrogen storage problem, which essentially means minimizing the enormous volume of hydrogen gas to achieve optimum gravimetric and volumetric density synergistically. This chapter briefly discusses the significant challenges, especially the hydrogen storage problem in the path of the development of a hydrogen-based economy and the possible approaches to meet the challenges.
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