Preparation and structural properties of Pd nanoparticles in layered silicate

Pd nanocrystals in the 5-15 nm ranges were prepared on pillared clay minera ls (PILCs) as supports by immobilizing Pd nanoparticles in the interlamella r space of montmorillonite and saponite by pillaring with aluminium hydroxi de 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 N-2, gas sorption measureme nts. The Pd/H interaction was characterized by H-2, sorption isotherms, whi ch revealed extensive sorption hysteresis depending on particle size. This effect calls attention to the potential use of Pd-PILC adsorbents for stora ge of gaseous H-2. Microcalorimetry was carried out to determine H-2, gas s orption 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 accessibili ty for hydrogen, H/Pd interactions are determined by the joint effect of th e external to total atomic ratio of Pd nanoparticles and the microporosity of the support pillared clays. (C) 2000 Elsevier Science B.V. All rights re served.