Two-dimensional gold nanostructures with high activity for selective oxidation of carbon-hydrogen bonds.

Liang Wang,Jian-Qiang Wang,Fudong Liu,Yu Han,Jianfeng Huang,Feng-Shou Xiao,Xiangju Meng,Jean-Marie Basset,Yihan Zhu

doi:10.1038/ncomms7957

Abstract

Efficient synthesis of stable two-dimensional (2D) noble metal catalysts is a challenging topic. Here we report the facile synthesis of 2D gold nanosheets via a wet chemistry method, by using layered double hydroxide as the template. Detailed characterization with electron microscopy and X-ray photoelectron spectroscopy demonstrates that the nanosheets are negatively charged and [001] oriented with thicknesses varying from single to a few atomic layers. X-ray absorption spectroscopy reveals unusually low gold–gold coordination numbers. These gold nanosheets exhibit high catalytic activity and stability in the solvent-free selective oxidation of carbon–hydrogen bonds with molecular oxygen.

Highlights

Efficient synthesis of stable two-dimensional (2D) noble metal catalysts is a challenging topic
It is known that with noble metals extraordinary catalytic activity occurs as a consequence of the quantum size effect when the catalyst contains only two to three atomic layers32–34. 2D Au nanostructures have been prepared on well-defined crystal surfaces by physical deposition methods[32,35,36]
The Au species could be clearly distinguished from the Layered double hydroxides (LDHs) substrate in the high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) images by the Z-contrast, which exhibited two kinds of typical morphologies: nanoparticles (NPs) in a size range of 2–10 nm; and irregular NSs with sizes ranging from several nanometers to tens of nanometers (Fig. 2, Supplementary Fig. 2)

Summary

Introduction

Efficient synthesis of stable two-dimensional (2D) noble metal catalysts is a challenging topic. X-ray absorption spectroscopy reveals unusually low gold–gold coordination numbers These gold nanosheets exhibit high catalytic activity and stability in the solvent-free selective oxidation of carbon–hydrogen bonds with molecular oxygen. 2D Au nanostructures have been prepared on well-defined crystal surfaces by physical deposition methods[32,35,36] They have controllable thicknesses within the range of a few layers of atoms and limited size (several nanometers) in the other two dimensions, and they are usually referred to as ‘islands’[32,35,36]. 2D metallic materials are supposed to show distinct molecular activation ability and catalytic behaviours, considering that they have unusual electronic structures as well as a large proportion of low-coordinated atoms. One attractive feature of LDH materials is that the interlayered anions have considerable freedom of movement to be substituted by other types of anions via ion exchange[38,39,40,41,42]

Methods

Results

Conclusion