Facile Synthesis of Ceria Nanocrystals with Tuneable Size and Shape
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MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.25
Facile Synthesis of Ceria Nanocrystals with Tuneable Size and Shape Can Li1, Yiliang Luan1, Bo Zhao2, Amar Kumbhar3, Fan Zhang4, Jiye Fang1,4* 1
Department of Chemistry, State University of New York at Binghamton, New York, USA
2
College of Arts & Sciences Microscopy, Texas Tech University, Texas, USA
3 Chapel Hill Analytical and Nanofabrication Laboratory, University of North Carolina at Chapel Hill, North Carolina, USA
4 Materials Science and Engineering Program, State University of New York at Binghamton, New York, USA
ABSTRACT
Ceria (CeO2) possesses a distinctive redox property due to a reversible conversion to its nonstoichiometric oxide and has been considered as a promising catalyst in the oxidative coupling of methane. Since a heterogeneously catalytic process usually takes place only on the surface of catalysts, it is reasonably expected that the performance of a catalyst, such as CeO2, highly relies on its size- and shape-dependent surface structure. We report our recent progress in achieving exclusive crystal facet-terminated CeO2 nanocrystals using a shapecontrolled synthesis protocol in a one-pot colloidal system. We modified a two-phase solvothermal approach to fabricate cubic and truncated octahedral CeO2 nanocrystals with a size-control. During the two-phase solvothermal process, we propose that the Ce-precursors transfer from the aqueous layer to the interface of the organic phase, promoted by the capping ligands (as known as phase-transfer catalysts), for the oxidation and nucleation, and subsequently form CeO2 nanocrystals in the organic layer. As different capping ligands favor binding on diverse crystal facets, tuning the composition of the capping ligand with a precise control could generate nanocrystals that are dominated by a single type of facets with a relatively narrow size distribution.
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INTRODUCTION As a most abundant rare earth element, cerium is now widely used in various fields, such as magnetics and catalysis[1-6]. Its oxide, ceria (CeO2), is mainly utilized as a catalyst support or a catalyst directly. The typical examples include applications in three-way catalysts, fuel cell catalysts, solar cell media, and the methanol couple oxidation catalysts[6-11]. CeO2, with a cubic crystal structure (Fm ̅ m, 225), is also one of the most common catalysts for the oxidative coupling of methane. In order to enhance the size- and shape-dependent catalytic performance of CeO2 nanocrystals, the development of an improved synthetic strategy with a surface character-control is potentially significant and has drawn growing attention recently[5, 12, 13]. In this study, we designed and fabricated size-controlled cubic, truncated octahedral and octahedral CeO2 nanocrystals by adopting a
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