Monitoring phase behavior of hydrogen confined in carbon nanopores by in-situ small angle neutron scattering technique

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 m ²/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 technique. 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 H ₂ 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.