Contributions of distinct gold species to catalytic reactivity for carbon monoxide oxidation.

Li-Wen Guo,Chun-Jiang Jia,Jie Zeng,Yu-Ying Huang,Pei-Pei Du,Ya-Wen Zhang,Xin-Pu Fu,Rui Si,Chao Ma,Chun-Hua Yan

doi:10.1038/ncomms13481

Abstract

Small-size (<5 nm) gold nanostructures supported on reducible metal oxides have been widely investigated because of the unique catalytic properties they exhibit in diverse redox reactions. However, arguments about the nature of the gold active site have continued for two decades, due to the lack of comparable catalyst systems with specific gold species, as well as the scarcity of direct experimental evidence for the reaction mechanism under realistic working conditions. Here we report the determination of the contribution of single atoms, clusters and particles to the oxidation of carbon monoxide at room temperature, by the aid of in situ X-ray absorption fine structure analysis and in situ diffuse reflectance infrared Fourier transform spectroscopy. We find that the metallic gold component in clusters or particles plays a much more critical role as the active site than the cationic single-atom gold species for the room-temperature carbon monoxide oxidation reaction.

Highlights

Small-size (o5 nm) gold nanostructures supported on reducible metal oxides have been widely investigated because of the unique catalytic properties they exhibit in diverse redox reactions
The corresponding X-ray photoelectron spectroscopy spectra confirmed that similar ratios of Ce3 þ /Ce4 þ were present in the ceria nanorods for all the tested samples, whether as-prepared or used after the CO oxidation reaction (Supplementary Fig. 3 and Supplementary Methods)
The structural and textural properties of CeO2 were identical for all three gold catalysts and they are suitable for the investigation of the role of different gold species in the catalysis

Summary

Introduction

Small-size (o5 nm) gold nanostructures supported on reducible metal oxides have been widely investigated because of the unique catalytic properties they exhibit in diverse redox reactions. We find that the metallic gold component in clusters or particles plays a much more critical role as the active site than the cationic single-atom gold species for the room-temperature carbon monoxide oxidation reaction. Some efforts have been made using measurements such as high-resolution transmission electron microscopy (HRTEM)[4,11,14,21,22,23] and X-ray absorption fine structure (XAFS)[12,17,18,24,25,26,27], the precise in situ characterization of specific gold species, single atoms, ultra-fine (o2 nm) clusters and small-size (2–5 nm) particles, is still in great demand. We report a facile synthesis of unique gold structures, including single atoms (Au_atom), o2 nm clusters (Au_cluster) and 3–4 nm particles (Au_particle) anchored to CeO2 nanorods These gold-ceria catalysts show distinct reactivity for room-temperature CO oxidation. This work provides an opportunity to build a fundamental understanding of electronic and local coordination structure of the active site at the atomic level in the Au–CeO2 system

Methods

Results

Conclusion