Abstract
On a long path of finding appropriate materials to store hydrogen, graphene and carbon nanotubes have drawn a lot of attention as potential storage materials. Their advantages lie at hand since those materials provide a large surface area (which can be used for physisorption), are cheap compared to metal hydrides, are abundant nearly everywhere, and most importantly, can increase safety to existing storage solutions. Therefore, a great variety of theoretical studies were employed to study those materials. After a benchmark study of different van-der-Waals corrections to Generalized Gradient Approximation (GGA), the present Density Functional Theory (DFT) study employs Tkatchenko–Scheffler (TS) correction to study the influence of vacancy and Stone–Wales defects in graphene on the physisorption of the hydrogen molecule. Furthermore, we investigate a large-angle (1,0) grain boundary as well as the adsorption behaviour of Penta-Octa-Penta (POP)-graphene.
Highlights
On the quest for environmentally-friendly energy generation, chemical energy released during formation of a water molecule out of hydrogen atoms reacting with atmospheric oxygen has been proposed as a possible route
In order to take into account the van-der-Waals interaction, various dispersion correction methods (DFT-D2 [34], Density Functional Theory (DFT)-D3 [35], DFT-TS [24,36]) implemented in VASP were tested for their ability to reproduce experimental lattice parameters of graphite and graphene
We start with testing the DFT-TS method against literature data, which was obtained by employing Grimme’s D3 method (DFT-D3)
Summary
On the quest for environmentally-friendly energy generation, chemical energy released during formation of a water molecule out of hydrogen atoms reacting with atmospheric oxygen has been proposed as a possible route. Carbon-based nano-structured materials have been suggested as promising candidates for hydrogen storage [1]. It was the discoverers [2] of graphene themselves, who first showed that the novel 2D material could store hydrogen at cryogenic temperatures and release it again at higher temperatures [3]. In order to tune the material response further, chemical as well as structural modifications to graphene can be introduced These include, e.g., metal decoration [10,11,12,13] or application of perforated graphene [14,15]. We consider impact of structural defects on the local adsorption properties and try to extract simple rule-of-thumb guidelines which can be used to steer further optimization of the carbon-based materials for H2 storage
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