Diachronic evolvement from tetra-icosahedral to quasi-hexagonal close-packed bimetal clusters

Abstract

Here we report a diachronic evolvement from tetra-icosahedral Au₃₀Ag₁₂(CCR)₂₄ to quasi-hcp (hexagonal close-packed) Au₄₇Ag₁₉(CCR)₃₂via a one-step reduction, in which the size/structure conversion of the two clusters is not a typical Oswald growth process, but involves interface shrinking followed by core rearrangement and surface polymerization. Au₃₀Ag₁₂(CCR)₂₄ has an aesthetic Au₁₈Ag₈ kernel that is composed of four interpenetrating Au₁₀Ag₃ icosahedra, while Au₄₇Ag₁₉(CCR)₃₂ has a twisted Au₁₉ core capped by a Au₁₂Ag₁₉ shell that are stacked in a layer-by-layer manner with a quasi-hcp pattern. The discovery of the two clusters not only provides further evidence for icosahedral clusters with longer excited-state lifetime compared to hcp-like clusters, but also discloses a double increase in catalytic reactivity for electrocatalytic oxidation of ethanol over quasi-hcp clusters in comparison with icosahedral clusters. This work provides the rationale for reversing the bottom-up growth process to remake bimetal clusters.