Tuning the pore structure and surface chemistry of porous graphene for CO2 capture and H2 storage

Porous graphene materials (PGMs) have been fabricated through CO2 and KOH activation of thermal exfoliated graphite oxide. The CO2 activated PGMs (CPGMs) display a three-dimensional morphology with hierarchical pore structure, while the KOH activated PGMs (KPGMs) exhibit a two-dimensional sheet morphology with numerous micropores and small mesopores. By adjusting the activation conditions, their specific surface areas and pore volumes can be easily tuned in a wide range. Moreover, the as-prepared PGMs show various surface chemistry, in which the CPGMs own a high content of quinone and carbonyl groups, and the KPGMs possess abundant hydroxyl groups. Gas adsorption experiments demonstrate that CO2 and H-2 uptakes of PGMs are affected by both their pore structure and surface chemistry. Notably, the KPGMs-7 has the highest CO2 uptake of 17.87 wt% (4.06 mmol g(-1)) at 273 K and 1 bar and H2 uptake of 2.41 wt% (11.88 mmol g(-1)) at 77 K and 1 bar, respectively.