Template-Free Synthesis of Sphere, Rod and Prism Morphologies of CeO 2 Oxidation Catalysts
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Template-Free Synthesis of Sphere, Rod and Prism Morphologies of CeO2 Oxidation Catalysts Yejun Guan • Emiel J. M. Hensen • Yan Liu Haidong Zhang • Zhaochi Feng • Can Li
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Received: 23 December 2009 / Accepted: 9 April 2010 / Published online: 22 April 2010 Ó Springer Science+Business Media, LLC 2010
Abstract Ceria materials with sphere, rod, and prism morphologies were synthesized via the hydrolysis of solutions containing Ce(NO3)3 and urea under hydrothermal conditions. By carefully adjusting the synthesis conditions (salt concentration, temperature and synthesis time), spheres with a diameter of about 200 nm, rods of about 6 nm in width and 60 nm in length and prisms with an edge length of about 600 nm were synthesized. XRD and TEM indicate that the grain size of these samples is in the range of 7–10 nm after calcination at 450 °C. These ceria materials exhibit a higher catalytic activity in the oxidation of CO than conventionally prepared CeO2. Keywords Ceria Hydrothermal synthesis Morphology Carbon monoxide oxidation
Y. Guan (&) H. Zhang Z. Feng C. Li (&) State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China e-mail: [email protected] C. Li e-mail: [email protected] E. J. M. Hensen Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands Y. Liu Institute of Chemical and Engineering Sciences (ICES), 1 Pesek Road, Jurong Island, Singapore 627833, Singapore
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1 Introduction Low-dimensional nanostructured materials attract considerable attention due to their unique physicochemical properties and their widespread applications in nanoscale devices and catalysis [1, 2]. Ceria is an important material used in a variety of applications such as in the automotive three-way catalyst, for the removal of volatile organic compounds (VOCs) and for the water–gas shift reaction [3–7]. The importance of ceria in catalysis is related to its redox and oxygen storage properties [8]. Surface oxygen vacancies of ceria participate in the activation of oxygen and also stabilize metal nanoparticles dispersed on its surface [9]. The stability and energy of formation of these oxygen vacancies differ between the surface and the bulk of ceria and also depend on the exposed surface planes [10, 11]. The surface reactivity relates to the exposed low index surface planes and an enhancement effect for CO oxidation has been reported on ceria nanorods made by different precursors [12, 13]. Related is the oxygen storage capacity which differs for ceria nanorods, nanoparticles, and polycrystalline ceria [14]. Furthermore, boundary regions between different planes may also contribute to the catalytic activity as shown for CeO2 nanotubes by Botana and et al. [15]. Thus it is desirable to prepare ceria-based materials in specific morphologies like fine particles, rods, or tubes, which present surfaces of large specific surface area. Generally, ceria with a rod shaped morphology can be
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