Enhanced hydrogen adsorption in ordered mesoporous carbon through clathrate formation

Ordered mesoporous carbons were synthesized with a soft-template approach and modified with a water and tetrahydrofuran mixture having a H₂O/THF molar ratio of 17:1 as potential adsorbent media for hydrogen storage. Hydrogen adsorption equilibrium on the carbon adsorbents was measured gravimetrically at 270 K and hydrogen pressures up to 163 bar. Enhanced hydrogen adsorption was observed on the carbon adsorbents doped with 0.5 wt.% and 0.75 wt.% of H₂O/THF due to the combined effects of hydrogen adsorption on the carbon surface and formation of a binary H₂-H₂O-THF clathrate. Hydrogen adsorption capacities on the carbon adsorbents doped with 0.5 wt.%, 0.75 wt.% of H₂O/THF, and the pure carbon at 270 K and 163 bar are 0.747 wt.%, 0.646 wt.% and 0.585 wt.%, respectively. The hydrogen adsorption isotherms on all the doped carbon adsorbents are of typical Type III and can be well correlated by the Freundlich equation. A desorption hysteresis loop was observed on the carbon adsorbents doped with 0.5 wt.% and 0.75 wt.% of H₂O/THF, which was probably caused by the pore size difference during the adsorption and desorption steps.