Surface-Structure Sensitivity of CeO2 Nanocrystals in Photocatalysis and Enhancing the Reactivity with Nanogold

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• 作者：Wanying Lei ; Tingting Zhang ; Lin Gu ; Ping Liu ; Jos茅 A. Rodriguez ; Gang Liu ; Minghua Liu
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：July 2, 2015
• 年：2015
• 卷：5
• 期：7
• 页码：4385-4393
• 全文大小：630K
• ISSN：2155-5435

文摘

Structure鈥揻unction correlations are a central theme in heterogeneous (photo)catalysis. In this study, using aberration-corrected scanning transmission electron microscopy (STEM), the atomic surface structures of well-defined one-dimensional (1D) CeO₂ nanorods (NRs) and 3D nanocubes (NCs) are directly visualized at subangstrom resolution. CeO₂ NCs predominantly expose the {100} facet, with {110} and {111} as minor cutoff facets at the respective edges and corners. Notably, the outermost surface layer of the {100} facet is nearly O-terminated. Neither surface relaxations nor reconstructions on {100} are observed, indicating unusual polarity compensation, which is primarily mediated by near-surface oxygen vacancies. In contrast, the surface of CeO₂ NRs is highly stepped, with the enclosed {110} facet exposing Ce cations and O anions on terraces. On the basis of STEM profile-view imaging and electronic structure analysis, the photoreactivity of CeO₂ nanocrystals toward aqueous methyl orange degradation under UV is revealed to be surface-structure-sensitive, following the order: {110} 鈮?{100}. The underlying surface-structure sensitivity can be attributed to the variation in low-coordinate surface cerium cations between {110} and {100} facets. To further enhance light absorption, Au nanoparticles (NPs) are deposited on CeO₂ NRs to form Au/CeO₂ plasmonic nanocomposites, which dramatically promotes the photoreactivity that is Au particle size- and excitation light wavelength-dependent. The mechanisms responsible for the enhancement of photocatalytic activity are discussed, highlighting the crucial role of photoexcited charge carrier transfer.