Researchers at the Chinese Academy of Sciences have developed a type of activated carbon with a high surface area of up to 3,190 m2 g-1 and a gravimetric hydrogen uptake capacity of 7.08 wt % at 77 K and 20 Bar—one of the largest for porous carbon materials. The results suggests that porous carbon with large amounts of active sites, high surface area, and high micropore volume related to optimum pore size could achieve high gravimetric hydrogen storage.
|Hydrogen uptake of different activated carbons. Credit: ACS. Click to enlarge.|
The activated carbons may also possess wide application in fields ranging from catalysts to energy conversion, the researchers noted. A paper on their work was published online 30 April in the Journal of the American Chemical Society.
There are two general types of activation procedures, physical and chemical. Physical activation involves gasification of the carbon materials in the presence of suitable oxidizing gasifying agents, such as CO2 and steam. Chemical activation relies on the reaction between a chemical agents such as KOH (potassium hydroxide) and the carbon materials.
Huanlei Wang, Qiuming Gao, and Juan Hu used both approaches in the study. They found that compared to CO2 activation, KOH activation can “remarkably” change pore structures of the activated carbon.
An enhanced hydrogen uptake of 7.08 wt % was successfully achieved for the as-obtained porous carbon AC-K5 at 77 K and 20 bar. The results indicate that the second activated carbons are promising materials for hydrogen storage, and higher gravimetric hydrogen uptake could be obtained if one can improve the microporosity with high surface area related to optimum pore size distribution and increase the number of active sites.—Wang et al. (2009)
Huanlei Wang, Qiuming Gao, and Juan Hu (2009) High Hydrogen Storage Capacity of Porous Carbons Prepared by Using Activated Carbon. J. Am. Chem. Soc., Article ASAP doi: 10.1021/ja8083225