Hexoctahedral Gold Nanoparticles Enclosed by High-Index {651} Facets as Electrocatalysts for Methanol Oxidation and Surface-Enhanced Raman Spectroscopy Substrates

The controllable preparation of gold nanoparticles (Au NPs) is of paramount importance for tuning their properties and characteristics. Herein, we report a facile, seed-mediated growth strategy involving the overgrowth of Au nanorods (NRs) for fabricating monodispersed Au NPs with controllable shapes and well-defined facets, such as hexoctahedral (HOH) Au NPs enclosed by high-index {651} facets, elongated tetrahexahedral (ETHH) Au NPs enclosed by high-index {730} facets, and octahedral (OCT) and tetrahedral (TET) Au NPs with low-index {111} facets. The underpotential deposition (UPD) of Ag and the [HAuCl4]/[Au NR] ratio are key factors for the formation of morphology-tunable Au NPs. The numerous active atoms on the high-index facets, sharp tips, and edges are energetically and kinetically favorable, facilitating the use of these NPs as both active catalysts and surface-enhanced Raman scattering (SERS) substrates. In comparison with the low-index-faceted Au NPs, the as-synthesized Au NPs with high-index facets (especially HOH Au NPs with {651} facets) demonstrate superior catalytic activity toward electrooxidation of methanol. Moreover, HOH Au NP substrates exhibit superior SERS performance, and a low detection limit (10–10 M) for 4-aminothiophenol (4-ATP) was determined. These results indicate that our HOH Au NPs have great potential in electrocatalysis, SERS detection, and direct methanol fuel cells for many practical applications.