title: Hydrogen spillover in Pt-single-walled carbon nanotube composites: formation of stable C-H bonds.
abstract: Using in situ electrical conductivity and ex situ X-ray photoelectron spectroscopy (XPS) measurements, we have examined how the hydrogen uptake of single-walled carbon nanotubes (SWNTs) is influenced by the addition of Pt nanoparticles. The conductivity of platinum-sputtered single-walled carbon nanotubes (Pt-SWNTs) during molecular hydrogen exposure decreased more rapidly than that of the corresponding pure SWNTs, which supports a hydrogenation mechanism facilitated by "spillover" of dissociated hydrogen from the Pt nanoparticles. C 1s XPS spectra indicate that the Pt-SWNTs store hydrogen by means of chemisorption, that is, covalent C-H bond formation: molecular hydrogen charging at elevated pressure (8.27 bar) and room temperature yielded Pt-SWNTs with up to 16 ± 1.5 at. % sp(3)-hybridized carbon atoms, which corresponds to a hydrogen-storage capacity of 1.2 wt % (excluding the weight of Pt nanoparticles). Pt-SWNTs prepared by the Langmuir-Blodgett (LB) technique exhibited the highest Pt/SWNT ratio and also the best hydrogen uptake.
authors.affiliation: Department of Material Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: Ranadeep
authors.initials: R
authors.lastname: Bhowmick
authors.forename: Srivats
authors.initials: S
authors.lastname: Rajasekaran
authors.forename: Daniel
authors.initials: D
authors.lastname: Friebel
authors.forename: Cara
authors.initials: C
authors.lastname: Beasley
authors.forename: Liying
authors.initials: L
authors.lastname: Jiao
authors.forename: Hirohito
authors.initials: H
authors.lastname: Ogasawara
authors.forename: Hongjie
authors.initials: H
authors.lastname: Dai
authors.forename: Bruce
authors.initials: B
authors.lastname: Clemens
authors.forename: Anders
authors.initials: A
authors.lastname: Nilsson