Mechanism of Hydrogen Storage in the Graphene Nanoflake–Lithium–H₂ System

Abstract

Carbon materials, such as graphene nanoflakes, carbon nanotubes, and fullerenes, can be used for hydrogen storage. Alkali doping of these materials generally increases their H2-storage density. In this study, the interaction of hydrogen molecules with Li-doped graphene nanoflakes was systematically investigated using density functional theory (DFT). A large polycyclic aromatic hydrocarbon composed of 37 benzene rings (referred to as GR) was used as a model of a graphene nanoflake, and GR–Li–(H2) n and GR–Li+–(H2) n (n = 0–13) clusters were used as hydrogen storage systems. The first and second coordination shells of H2 around GR–Li were saturated at n = 3 and 7, respectively. The binding energy of H2 to GR–Li decreased with increasing n, reaching a limiting value at n = 10. For GR–Li+–(H2) n , similar results were obtained and the Li atom on GR was shown to be activated by electron transfer from Li to GR. The diffusion barrier of Li+ on GR decreased upon addition of H2 to Li+ from 6.35 (n = 0) to 3.62 kcal/mol (n = 4). The mechanism of H2 addition is discussed herein based on the calculated results.

C60Con complexes as hydrogen adsorbing materials

“…An interesting group has been termed sorbent materials [2,3]. These include, among others, carbon nanotubes [4][5][6], boron nitride nanotubes [7,8], inorganic and organic fullerenes [9,10], graphene nanoflakes [11,12], porous carbons [13][14][15][16][17][18][19], mesoporous silica [3], metal-organic frameworks (MOFs) [19], covalent-organic frameworks (COFs) [20], and clathrates [21]. In these, hydrogen is bound to the substrate by physisorption forces [22,23], so the systems are good hydrogen adsorbers only at low temperature.…”

Hydrogen Storages Based on Graphene Nano-Flakes: Density Functional Theory Approach

“…However, the effects of Li on the H2 storage mechanism and capacity of GNF are not clearly understood. In this section, DFT studies on the mechanism of hydrogen storage due to GNFs doped by Li-metals are presented [38].…”

Synthesis of holey graphene for advanced nanotechnological applications

“… 153 It is believed that the hydrogen storage mechanism varies from sample to sample. 154 The interaction between hydrogen and carbon materials is governed by van der Waals force. This attractive force could lead to physisorption.…”