title: Au nanocube-directed fabrication of Au-Pd core-shell nanocrystals with tetrahexahedral, concave octahedral, and octahedral structures and their electrocatalytic activity.
abstract: In this study, we have successfully developed a facile method for the high-yield fabrication of Au-Pd core-shell heterostructures with an unusual tetrahexahedral (THH) morphology using Au nanocubes as the structure-directing cores. The lattice orientations of the Au nanocubes match those of the Pd shells. Structural analysis establishes that the THH nanocrystals are bounded by high-index {730} facets. A substantial lattice mismatch between Au and Pd, oxidative etching in the presence of chloride and oxygen, the use of cetyltrimethylammonium chloride (CTAC) surfactant, and the reaction temperature (30-60 °C) were identified to be key factors facilitating the formation of the THH core-shell nanocrystals. Intermediate products have also been examined to follow the growth process. By selecting cubic gold cores with sizes of 30-70 nm and varying the volume of the gold core solution used, THH Au-Pd core-shell nanocrystals with continuously adjustable sizes from 56 to 124 nm can be readily obtained. Their UV-vis spectra display progressive red-shifted bands. Interestingly, novel concave octahedral and octahedral Au-Pd core-shell nanocrystals can be prepared by lowering the reaction temperature and prolonging the reaction time. The concave octahedra show depressions on all the {111} faces. Electrocatalytic activity of the three Au-Pd core-shell structures for the oxidation of ethanol has been investigated. The THH nanocrystals with entirely high-index {730} facets were found to exhibit the best electrocatalytic activity. These size-tunable THH Au-Pd core-shell nanocrystals may be valuable for catalyzing other organic reactions.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Chun-Lun
authors.initials: CL
authors.lastname: Lu
authors.forename: Kariate Sudhakara
authors.initials: KS
authors.lastname: Prasad
authors.forename: Hsin-Lun
authors.initials: HL
authors.lastname: Wu
authors.forename: Ja-an Annie
authors.initials: JA
authors.lastname: Ho
authors.forename: Michael H
authors.initials: MH
authors.lastname: Huang