Hyperstoichiometric hydrogen storage in monodispersed palladium nanoparticles

Palladium nanoparticles are synthesized using a surfactant-mediated condensed-phase reduction-reaction and their moderate ambience hydrogen adsorption is studied using the Sievert’s volumetric equipment. The average nanoparticle-diameters are found to be 13.0 ± 4.8 and 7.7 ± 3.2 nm when the amount of the surfactant – trioctyl phosphine oxide (TOPO) varied from 0.2 to 0.3 g. The hydrogen storage capacity of these particles measured at 298 K and a hydrogen pressure of 1.6 MPa is found to be 1.05 ± 0.01 wt%. As-formed hyperstoichiometric hydride PdH1.12 does not show considerable lattice expansion indicating that hydrogen is mostly adsorbed on surface and subsurface sites. Re-adsorption of hydrogen on samples dehydrogenated at 200 °C suggests that nanoparticles do not compromise their reversible storage capacity upon hydrogenation–dehydrogenation cycles.