Preparation and structural properties of Pd nanoparticles in layered silicate

Pd nanocrystals in the 5–15 nm ranges were prepared on pillared clay minerals (PILCs) as supports by immobilizing Pd nanoparticles in the interlamellar space of montmorillonite and saponite by pillaring with aluminium hydroxide cations. Pd nanoparticles were generated via reduction by ethanol of Pd acetate present in the adsorption layer at room temperature. The structure of Pd-PILC samples was characterized by XRD and N2 gas sorption measurements. The Pd/H interaction was characterized by H2 sorption isotherms, which revealed extensive sorption hysteresis depending on particle size. This effect calls attention to the potential use of Pd-PILC adsorbents for storage of gaseous H2. Microcalorimetry was carried out to determine H2 gas sorption enthalpy isotherms, which also exhibited a sorption hysteresis. By combining the data, H/Pd interactions are also expressed as molar sorption enthalpies. It is concluded that, due to differences in surface accessibility for hydrogen, H/Pd interactions are determined by the joint effect of the external to total atomic ratio of Pd nanoparticles and the microporosity of the support pillared clays.