Atomically Precise Fcc-Amorphous Homometal Heterojunction with ∼1 nm Size

The emerging of ultrasmall gold nanoparticles (nanoclusters) with atomic precision provides opportunities for precisely studying crystalline-amorphous heterostructures, despite the construction of such structures being challenging. In this work, we developed an acid-induction method and synthesized a Au₅₂(TBBT)₃₀ (TBBTH = 4-tert-butylbenzenelthiol) nanocluster with the kernel composed of two parts: the amorphous Au₂₂ part and the fcc Au₂₁ part, which represents the first construction of fcc-amorphous homometal heterojunction with ∼1 nm size. Density function theory (DFT) revealed that the HOMO-LUMO majorly distributed in the amorphous part and the HOMO-LUMO gap was dominated by the amorphous part, indicating the redox activity of the amorphous Au₂₂ part in contrast to the fcc Au₂₁ part, which was experimentally confirmed by differential pulse voltammetry, antioxidation test and anti-Galvanic reaction. But for electro-catalyzing reduction of CO₂ to CO, the crystalline surface sites were revealed to be more catalytically active than the amorphous surface sites in catalyzing the reduction of CO₂ to CO, and the most active sites were assigned to the cosurface sites of amorphous Au₂₂ and fcc Au₂₁, which is also responsible for the high performance of Au₅₂(TBBT)₃₀ relative to the pure fcc-structured Au₅₂(TBBT)₃₂ (the highest CO FE: 96.7% at -0.67 V vs 73.3% at -0.57 V; CO partial current density at the corresponding potential: -7.3 vs -2.7 mA cm^-2).