Hydrogen storage inside graphene-oxide frameworks

Abstract

In this paper, we use applied mathematical modelling to investigate the storage ofhydrogen molecules inside graphene-oxide frameworks, which comprise two parallelgraphenes rigidly separated by perpendicular ligands. Hydrogen uptake is calculated forgraphene-oxide frameworks using the continuous approximation and an equation of statefor both the bulk and adsorption gas phases. We first validate our approach byobtaining results for two parallel graphene sheets. This result agrees well with anexisting theoretical result, namely 1.85 wt% from our calculations, and 2 wt% arisingfrom an ab initio and grand canonical Monte Carlo calculation. This providesconfidence to the determination of the hydrogen uptake for the four graphene-oxideframeworks, GOF-120, GOF-66, GOF-28 and GOF-6, and we obtain 1.68, 2,6.33 and 0 wt%, respectively. The high value obtained for GOF-28 may be partlyexplained by the fact that the benzenediboronic acid pillars between graphenesheets not only provide mechanical support and porous spaces for the molecularstructure but also provide the higher binding energy to enhance the hydrogenstorage inside graphene-oxide frameworks. For the other three structures, thisbinding energy is not as large in comparison to that of GOF-28 and this effectdiminishes as the ligand density decreases. In the absence of conflicting data, thepresent work indicates GOF-28 as a likely contender for practical hydrogen storage.