NMR Characterization of Hydrogen Adsorption and Pore Structures of Carbon-Based Materials*

Hydrogen adsorption in carbon-based materials such as boron-doped graphite and carbon aero gels were investigated by nuclear magnetic resonance (NMR). $^{1}$H NMR is shown to be a sensitive and quantitative probe for detecting adsorbed gas molecules such as H$_{2}$, methane, and ethane. NMR measurements were carried out in-situ under given H$_{2}$ pressure up to a pressure of over 100 atm, at room temperature and 100 K. From such $^{1}$H NMR measurement, the amount of adsorbed H$_{2}$ molecules was determined versus pressure. In addition to measuring adsorption binding energies via isotherms, the structure and distribution of the nanopores within the material were characterized in order to relate the size of the pores to the rate of diffusion of the H$_{2}$ to the adsorption sites.