Influence of surface treatments on micropore structure and hydrogen adsorption behavior of nanoporous carbons

The scope of this work was to control the pore sizes of porous carbons by various surface treatments and to investigate the relation between pore structures and hydrogen adsorption capacity. The effects of various surface treatments (i.e., gas-phase ozone, anodic oxidation, fluorination, and oxygen plasma) on the micropore structures of porous carbons were investigated by N₂/77 K isothermal adsorption. The hydrogen adsorption capacity was measured by H₂ isothermal adsorption at 77 K. In the result, the specific surface area and micropore volume of all of the treated samples were slightly decreased due to the micropore filling or pore collapsing behaviors. It was also found that in F₂-treated carbons the center of the pore size distribution was shifted to left side, meaning that the average size of the micropores decreased. The F₂- and plasma-treated samples showed higher hydrogen storage capacities than did the other samples, the F₂-treated one being the best, indicating that the micropore size of the porous carbons played a key role in the hydrogen adsorption at 77 K.