Size-Dependent Hydrogen Sorption in Ultrasmall Pd Clusters Embedded in a Mesoporous Carbon Template

摘要

Abstract: Hydrogen sorption properties of ultrasmall Pd nanoparticles (2.5 nm) embedded in a mesoporousncarbon template have been determined and compared to those of the bulk system. Downsizing the Pdnparticle size introduces significant modifications of the hydrogen sorption properties. The total amount ofnstored hydrogen is decreased compared to bulk Pd. The hydrogenation of Pd nanoparticles induces anphase transformation from fcc to icosahedral structure, as proven by in situ XRD and EXAFS measurements.nThis phase transition is not encountered in bulk because the 5-fold symmetry is nontranslational. The kineticsnof desorption from hydrogenated Pd nanoparticles is faster than that of bulk, as demonstrated by TDSninvestigations. Moreover, the presence of Pd nanoparticles embedded in CT strongly affects the desorptionnfrom physisorbed hydrogen, which occurs at higher temperature in the hybrid material compared to thenpristine carbon template.