Rational selection of halide ions for synthesizing highly active Au@Pd nanobipyramids

Abstract

Pd-based nanostructures with stepped facets possess potential applications in many fields, particularly in catalysis. Generally, crystal growth often only allows the formation of nanostructures with energetically non-stepped facets, so it is desirable to develop methods that can be used to prepare Pd-based nanostructures bounded by stepped facets. Herein, penta-fold twinned (PFT) Au@Pd nanobipyramids (NBs) with stepped {100} facets were synthesized through growing Pd on Au decahedral nanoparticles (NPs) in polyol. During the growth of Au@Pd NBs, Br À was a critical factor, because it has appropriate affinity for the Pd atom and adjusted the growth rate ratio along h110i and h100i, resulting in the formation of Au@Pd NBs with stepped {100} facets. The product shape and size could be tailored by controlling the reaction conditions. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS), high angle annular dark field (HAADF) imaging and scanning transmission electron microscopy EDS (STEM-EDS) were used to investigate the structure and growth of the Au@Pd NBs. A growth mechanism involving two stages was elucidated. In the first stage, the growth of Pd clearly occurred along both h110i and h100i. In the second stage, the growth along h110i was faster than that along h100i. Furthermore, we also demonstrated that the as-prepared Au@Pd NBs had high catalytic activity, compared with Pd nanocubes and Pd-Au-Pd segmental nanorods.

Controlled Overgrowth of Five-Fold Concave Nanoparticles into Plasmonic Nanostars and Their Single-Particle Scattering Properties

“…The anisotropic growth can be driven as a combined effect of Cu 2+ ions and halide Cl – species. − The molar concentration of copper chloride strongly affected the growth rate. , Small multi-twinned Au NPs with {111}-exposed facets served as seeds for the second step of growth, where copper ions at a relatively low metal ratio (Cu/Au = 0.66) deposited along with Au adatoms on the available {001} facets. This process changed the {001} side facets in the regular decahedral NPs to {112} lateral facets present in the CPNPs (Figure d).…”