title: Binary Au/MWCNT and ternary Au/ZnO/MWCNT nanocomposites: synthesis, characterisation and catalytic performance.
abstract: Gold nanoparticles of 10-24 and 5-8 nm in size were obtained by chemical citrate reduction and UV photoreduction, respectively, on acid-treated multiwalled carbon nanotubes (MWCNTs) and on ZnO/MWCNT composites. The shape and size of the deposited Au nanoparticles were found to be dependent upon the synthetic method used. Single-crystalline, hexagonal gold particles were produced in the case of UV photoreduction on ZnO/MWCNT, whereas spherical Au particles were deposited on MWCNT when the chemical citrate reduction method was used. In the UV photoreduction route, n-doped ZnO serves as the e(-) donor, whereas the solvent is the hole trap. All materials were fully characterised by UV/Vis spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and BET surface analysis. The catalytic activity of the composites was studied for the selective hydrogenation of alpha,beta-unsaturated carbonyl compound 3,7-dimethyl-2,6-octadienal (citral). The Au/ZnO/MWCNT composite favours the formation of unsaturated alcohols (selectivity=50% at a citral conversion of 20%) due to the presence of single-crystalline, hexagonal gold particles, whereas saturated aldehyde formation is favoured in the case of the Au/MWCNT nanocomposite that contains spherical gold particles.
authors.affiliation: Fachbereich Chemie, Anorganische Chemie, Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstrasse 18, 64287 Darmstadt, Germany.
authors.forename: Jayaprakash
authors.initials: J
authors.lastname: Khanderi
authors.forename: Rudolf C
authors.initials: RC
authors.lastname: Hoffmann
authors.forename: Jörg
authors.initials: J
authors.lastname: Engstler
authors.forename: Jörg J
authors.initials: JJ
authors.lastname: Schneider
authors.forename: Jürgen
authors.initials: J
authors.lastname: Arras
authors.forename: Peter
authors.initials: P
authors.lastname: Claus
authors.forename: Gennady
authors.initials: G
authors.lastname: Cherkashinin