Hydrogen storage properties of copper and silver exchanged zeolite SSZ-13

Copper and silver cation-exchanged zeolite SSZ-13 present an interesting opportunity to study the mechanism of interaction of adsorbate gases, primarily hydrogen (H2), with the ion-exchange sites in zeolites as there is only one type of cation site, in contrast to many zeolites. Cation-exchange in zeolites has been shown to result in more H2 specific binding sites and higher adsorption capacity. Detg. the relationship between the H2-cation interaction and the type of cation is crit. to designing new types of H2 storage materials, including MOFs and porous carbons. The interaction of H2 with cation-exchanged zeolites can provide crit. information on the relative binding strengths to the zeolite host, as well as how the host framework changes as a function of the quantity of gas adsorbed. We present a multifaceted approach to the study of H2 adsorption in both copper- and silver-exchanged SSZ-13 and for comparison the host framework SSZ-13. Powder neutron diffraction was employed to locate each of the site specific binding sites for H2 from in situ adsorption allowing for the accurate detn. of the location of the adsorbed gas relative to the zeolite framework. Possible cation-migration as a function of adsorbed H2 is considered relative to that of gas adsorbed in cation-exchanged zeolites X and Y (FAU). Addnl., inelastic neutron scattering spectroscopy was used to probe the relative rotational energies of the adsorbed H2 as a function of the quantity of gas loaded. Low-pressure gas adsorption measurements reveal an increased H2 uptake in the cation-exchanged zeolites over that of the host framework without exchange.