Hydrogen storage capacity of carbon-based materials (carbon foams, nanotube bundles, etc.) is usually within ~3.0–6.0 wt.% at 77 K and moderate pressures of 50-70 bar. For comparison, the best metal–organic framework (MOF) adsorbs up to ~9 wt % (excess) of molecular hydrogen at the same conditions. Since MOFs are in general expensive and in most cases humidity-sensitive, we consider graphene-based nanostructures as a reasonable alternative for hydrogen storage applications. In the last years considerable attention has been focused on the chemistry of graphene-oxide (GO) frameworks (GOFs, alternatively called pillared graphene-oxide). Simulations on model systems gave promising results, with total uptake up to ~10 wt % (77 K). However, the actual structure of GOFs based on covalent cross-linking of GO-layers has to be ruled out because of observed significant swelling of the materials. Furthermore, the structures are usually microporous (pore volume = ~0.5 cm3/g) with surface areas close to 1000 m2/g. In line with Chahine’s rule, the storage capacity of such materials does not exceed 2 wt % (77 K). Recently, by KOH-activation of GO-powder and subsequent annealing in hydrogen atmosphere, so-called “3D graphene scaffolds” with high surface area (~3400 m2/g) and large pore volume (2.2 cm3/g) have been prepared. This material adsorbs ~7.5 wt % of H2 at 77 K (~50 bar). The structure of this material is rather irregular. As a model system that could approximate its structure, we suggested polycatenated layers of perforated graphene. The model, however, gave rise to a somewhat lower surface area and smaller uptake (6 wt %).
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