Adsorption and desorption behavior of titanium-decorated polycrystalline graphene toward hydrogen storage: a molecular dynamics study

Abstract

The hydrogen adsorption and desorption capacity of polycrystalline graphene sheets (PGs) with and without titanium (Ti) decoration is investigated using molecular dynamics simulations. Interatomic interactions of PGs are modeled using Tersoff potential, and the remainder of interactions are calculated via Lennard-Jones potential. The effect of grain size and Ti concentration on the mechanical properties and hydrogen adsorption capacity of PGs is studied. The presence of grain boundaries in PGs reduces their mechanical properties, while the decoration of Ti adatoms does not significantly alter the mechanical properties of PGs. PGs showed a ~ 57% increase in the gravimetric density of H 2 at 300 K and 50 bar compared to the pristine graphene sheet. At 100 bar pressure, PGs with 1% Ti concentration achieved a gravimetric density of 9.9 wt.% and 3.2 wt.% at 77 and 300 K, respectively. In Ti-decorated PGs, the desorption curve follows the same path at 300 K as the adsorption curve with increasing Ti concentration, and the desorption curve diverges from the adsorption curve after 1.5% Ti concentration at 77 K. The potential use of the isosteric enthalpy of adsorption to determine the adsorbent's capability for adsorbing H 2 molecules is also discussed.

Hetero-atom doped graphene for marvellous hydrogen storage: unveiling recent advances and future pathways

“…In the case of 1% Ti-decorated polycrystalline graphene, the HSC reaches 3.2 wt% at 300 K and 9.9 wt% at 77 K, both under a 100 bar pressure. 183 3.2.2.2. Titanium-decorated N/B-doped graphene for hydrogen storage.…”

Improvement of Hydrogen Adsorption on the Simultaneously Decorated Graphene Sheet with Titanium and Palladium Atoms

“…This metal is adsorbed in graphene with a high energy (−1.98 eV) 22 high capacity for storing hydrogen (9.9 wt % at 77 K). 23 However, cluster formation has limited its use in the hydrogen storage industry. In 2018, Yuan et al showed that the adsorption energy of the Ti atom on the graphene sheet was −3.65 eV.…”

Calcium-Decorated Polygon-Graphenes for Hydrogen Storage

“…However, due to the small size and gaseous nature of H 2 , efficient storage of H 2 is the main bottleneck for its practical applications. Recently, H 2 storage on surfaces of nanostructures such as graphene was suggested by adsorption of H 2 on their surfaces, which improves the quality by overcoming a high operating temperature and slow kinetics. − It has been found that transition metal atoms are decorated on carbon nanomaterials to store H 2 on a molecular form of H 2 because H 2 can be adsorbed on the metal atoms through the hybridization of metal “d” orbitals with H 2 “σ” and “σ*” orbitals, which is called Kubas-type H 2 storage materials. − …”

“…In this regard, Kubas-type H 2 storage materials have received much attention because they can be used for room-temperature H 2 storage, since the adsorption energy of H 2 fulfills the condition (∼0.2 to 0.4 eV) of room-temperature H 2 storage. − However, it has been found that the capability of H 2 storage at room temperature is diminished because metal clustering is in energy favorable due to their large cohesive energy (∼4 eV) . On the other hand, Kubas-type H 2 storage materials, multilayer Ti 2 CT x , have been synthesized and the performance of H 2 storage capability has been demonstrated .…”