Mesoporous carbons with KOH activated framework and their hydrogen adsorption

Abstract

The effects of KOH activation on pore structure of ordered mesoporous carbons were analyzed by transmission electron microscopy, powder X-ray diffraction and argon adsorption. The activation led to remarkable increases in micropore volume and BET surface area up to 1.0 mL g⁻¹ and 2700 m² g⁻¹, at the expense of the mesostructural order. The resultant carbons with various microporosity and mesoporosity were tested for room-temperature adsorption of hydrogen under high pressure. The adsorption data were analyzed in correlation with the varied carbon pore structures. The results showed that the hydrogen adsorption capacity increased approximately linearly with respect to micropore volume, or BET surface area, reaching a 2.5-times higher value when fully activated. However, the adsorption capacity at 100 atm (0.75 wt%) was still far below the US DOE target of 6.5 wt%. The extrapolation of our results to the carbon structure with the highest possible surface area could lead to no more than 2.5 wt%. This result suggests that chemisorption or other chemical storage methods should be combined with physisorption if carbon materials are considered for hydrogen storage.