Pore size effects of nanoporous carbons with ultra-high surface area on high-pressure hydrogen storage

In this work, the morphologies and pore structures of a series of corncob-derived activated carbons and zeolite templated carbon with ultrahigh surface area were carefully investigated by SEM, HRTEM and N-2-sorption characterization technologies. The high-pressure hydrogen uptake performance was analyzed using standard Pressure-Composition-Temperature apparatus in order to study the pore size effects on hydrogen uptake. These as-obtained porous carbons showed different characteristics of pore size distribution as well as specific surface area. The results indicate that the most effective pores for adsorbing hydrogen depended on the storage pressure. These ultramicropores (0.65-0.85 nm) could be the most effective pores on excess H-2 uptake at 1 bar, however, micropores (0.85-2 nm) would play a more important role in excess H-2 uptake at higher pressure at 77 K. At room temperature, pore size effects on H-2 uptake capacity were very weak. Both specific surface area and total pore volume play more important roles than pore size for H-2 uptake at room temperature, which was clearly different from that at 77 K. For applications in future, the corncob-derived activated carbons can be more available than zeolite templated carbons at 77 K. Element doping enhanced hydrogen uptake could be main research direction for improving H-2 uptake capacity at room temperature.