Abstract
We report on the use of in-situ small angle neutron scattering (SANS) technique to study the phase behavior of hydrogen confined in narrow pores of ultramicroporous carbon (UMC) with a very large surface area (2630 m2/g) and pore volume (1.3 cm3/g). The effect of pore size and pressure on hydrogen adsorbed on UMC at room temperature and pressures up to ~200 bar were investigated. In a previous experiment, we have measured the density of adsorbed H2 gas in the nanopores and mesopores of polyfurfuryl alcohol-derived activated carbon (PFAC) by SANS techniques. Here, a comparative SANS study between the UMC and PFAC was conducted in order to further investigate the densification of H2 as a function of pore size and pressure. Initial results suggest that the density of confined H2 in both UMC and PFAC is considerably higher than that of the bulk hydrogen gas. The density is systematically higher in the narrow pores and decreases with increasing pore size. These results clearly demonstrate the advantage of adsorptive storage over compressed gas storage and emphasize the greater efficiency of micropores over mesopores in the adsorption process, which can be used to guide the development of new carbon adsorbents tailored for maximum H2 storage capacities at near-ambient temperatures.
