Hydrogen Adsorption on Activated Carbon

The adsorption of hydrogen on carbon nanotubes and activated carbons has generated considerable interest in relation to hydrogen storage for fuel cells applications[1-3]. However, the widespread use of hydrogen as a fuel is limited by the lack of a convenient and cost-effective method of hydrogen storage. Adsorption of supercritical hydrogen is limited by the low interaction energy between hydrogen and the carbon surface, which is only enhanced in nanoporosity. Activated carbons have hydrophobic sites consisting of the graphene basal plane layers and hydrophilic sites comprising the functional groups. The hydrophobic graphene layer surfaces act as primary adsorption sites for neutral species, such as hydrogen, whereas the hydrophilic oxygen functional groups are primary sites for adsorption of polar species. It is envisaged that an adsorbent material consisting exclusively of ultramicropores with molecular dimensions could adsorb sufficient hydrogen to meet the requirements for transportation use. However, to date, there have only been limited detailed published studies of the results for hydrogen adsorption on carbon materials. In this study, we systematically investigate the influence of porous structure and functional groups characteristics on the adsorption/desorption of hydrogen on activated carbons. The effect of temperature on the amounts adsorbed and the adsorption dynamics of hydrogen on activated carbon were also studied.