TEM and STEM study of the Au nano-particles supported on metal oxides
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1026-C17-14
TEM and STEM study of the Au nano-particles supported on metal oxides Tomoki Akita1,2, Koji Tanaka1, Masanori Kohyama1,2, and Masatake Haruta2,3 1 Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology (AIST), Midorigaoka 1-8-31, Ikeda, Japan 2 JST CREST, Hon-cho 4-1-8, Kawaguchi, Saitama 332-0012, Japan 3 Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, MinamiOsawa1-1, Hachioji, Tokyo, Japan ABSTRACT Gold nano-particles were deposited on metal oxide substrates, TiO2 and CeO2, and the structures of Au particles and Au-metal oxide interfaces were observed by transmission electron microscopy (TEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). It was found that the growth of Au particles on TiO2 and CeO2 by heating treatment is suppressed in the reductive atmosphere compared to the oxidative atmosphere. The atomically resolved HAADF-STEM images in profile-view were successfully obtained for the Au/TiO2 and Au/CeO2 samples. Au particles tend to form flat interfaces supported on CeO2 substrates compared to TiO2 substrates. The incoherent atomic configuration was observed for the Au particle-CeO2 interface. INTRODUCTION It is well-known that Au nano-particles supported on metal oxides exhibits high catalytic activity. It was also pointed out that the catalytic properties of Au nano-particles are sensitive to the size of Au particles and the interface structure between Au and metal oxide support [1]. Some experimental results indicate that the perimeter of a Au particle on a metal oxide surface performs key roles for the low temperature CO oxidation, but the details are not understood. Thus, it is important to elucidate the structures of Au nano-particles and Au-metal oxide interfaces in atomic scale by electron microscopy. Recently, spherical aberration corrected TEM is used as powerful technique for the investigation of the surface and the interface structure without delocalization effects which occur in conventional high resolution transmission electron microscopy (HRTEM) method [2,3]. The high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) method is also powerful technique to observe the interface structure and the segregated impurity atoms [4,5]. It should be noted that the HAADFSTEM technique even without aberration corrector has advantage practically that the position of atomic columns is directly identified without image simulations which is indispensable for the interpretation of conventional HRTEM images. In this study, the Au particles are deposited on the TiO2 and CeO2 substrates as the model structure of Au catalysts, and the Au-metal oxide interfaces are observed by the HAADF-STEM. The growth of Au particles is also investigated for the heating temperature and heating atmosphere.
EXPERIMENT Gold nano-particles were supported on TiO2 and CeO2 substrates. Single crystalline TiO2 and poly crystalline CeO2 were used for substrates. P
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