Xue Mengmeng, Tan Yiwei
State Key Laboratory of Materials-Oriented Chemical Engineering, School of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing 210009, China.
Nanoscale. 2014 Nov 7;6(21):12500-14. doi: 10.1039/c4nr03603d.
A unique methodology having access to Au nanorods (AuNRs)-based hollow alloy nanostructures has been developed. The syntheses and characterization of the hollow Pt-Au nanoalloys with ellipsoidal and cylindrical shapes together with a rattle-type hollow Cu-Au nanoheterostructure are described. Unlike the conventional nanoscale Kirkendall process, the formation of these AuNRs-based hollow nanostructures occurs under extremely mild conditions, indicating a distinctive underlying mechanism. The key step for this present synthesis method is the incubation of AuNRs with CuCl2 at 60 °C in the presence of hexadecyltrimethylammonium bromide (CTAB) or hexadecyltrimethylammonium chloride (CTAC). The selective etching of the tips of AuNRs caused by Cu(2+) ions combined with the dissolved molecular oxygen promotes the generation of defects and vacancies, leading to a facile alloying reaction by the crystal fusion of AuNRs. Particularly, the results of the formation of the hollow nanoalloys in conjunction with various control experiments demonstrate that the halide ions that are specifically adsorbed on the AuNR surface afford sinks for vacancy accumulation and condensation during the unbalanced interdiffusion of alloying atoms, presumably because of the disproportion in the equilibrium concentration of vacancies. Thus, the void formation becomes kinetically favorable. The Pt-Au nanocages can provide modified surface electronic structures, resulting from their non-uniform crystalline structures and the surface segregation of Pt in the nanocages. These characteristics enable them to exhibit excellent electrocatalytic performance for the oxygen reduction reaction (ORR).
一种可制备基于金纳米棒（AuNRs）的中空合金纳米结构的独特方法已被开发出来。本文描述了具有椭圆形和圆柱形形状的中空Pt-Au纳米合金以及一种拨浪鼓型中空Cu-Au纳米异质结构的合成与表征。与传统的纳米级柯肯达尔过程不同，这些基于AuNRs的中空纳米结构的形成是在极其温和的条件下发生的，这表明其潜在机制独特。当前这种合成方法的关键步骤是在十六烷基三甲基溴化铵（CTAB）或十六烷基三甲基氯化铵（CTAC）存在的情况下，于60℃将AuNRs与CuCl₂孵育。由Cu(2+)离子与溶解的分子氧引起的AuNRs尖端的选择性蚀刻促进了缺陷和空位的产生，通过AuNRs的晶体融合导致了容易的合金化反应。特别地，中空纳米合金形成的结果以及各种对照实验表明，特异性吸附在AuNR表面的卤离子在合金化原子不平衡互扩散过程中为空位积累和凝聚提供了汇聚点，这可能是由于空位平衡浓度的不均衡。因此，空穴的形成在动力学上变得有利。Pt-Au纳米笼可以提供改性的表面电子结构，这源于它们不均匀的晶体结构以及Pt在纳米笼中的表面偏析。这些特性使它们在氧还原反应（ORR）中表现出优异的电催化性能。
