Applied Catalysis A: General 449 (2012) 96–104 Contents lists available at SciVerse ScienceDirect Applied Catalysis A: General jo u r n al hom epage: www.elsevier.com/locate/apcata Gold supported on ceria nanoparticles and nanotubes Brenda Acosta a,b , Elena Smolentseva c , Sergey Beloshapkin d , Ricardo Rangel e , Miguel Estrada a , Sergio Fuentes c , Andrey Simakov c,∗ a Posgrado en Física de Materiales, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, B.C. 22860, Mexico b Posgrado de la Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico c Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana a Ensenada, Ensenada, C.P. 22860, Baja California, Mexico d Materials & Surface Science Institute, University of Limerick, Limerick, Ireland e Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico a r t i c l e i n f o Article history: Received 11 May 2012 Received in revised form 20 September 2012 Accepted 22 September 2012 Available online 8 October 2012 Keywords: Ceria nanotubes Hydrothermal treatment Gold nanoparticles UV–vis in situ CO oxidation a b s t r a c t The ceria nanotubes with different size have been prepared via a hydrothermal treatment of CeO 2 nanoparticles at 120 ◦ C with two different NaOH concentrations (5 or 10 M) for 36 h. The synthesized ceria samples characterized by SEM, TEM, XRD, and UV–visible spectroscopy were used as supports for Au/CeO 2 catalysts preparation by DP technique using HAuCl 4 as gold precursor and urea as precipitation agent. The formation of gold nanoparticles (Au NPs) has been studied by TEM, in situ UV–visible–mass analysis at temperature programmed reduction and XPS spectroscopy. Three distinguishable steps in the formation of Au NPs accompanied by profound ceria reduction particular for ceria nanotubes have been found. Au NPs stabilized on the ceria nanotubes have been characterized with higher activity in CO oxidation than those supported on ceria nanoparticles. The structure and redox treatment of ceria nano- tubes affects size of Au NPs and their catalytic activity in CO oxidation. Pre-oxidized Au/CeO 2 -nanotubes manifest the highest activity in CO oxidation. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. 1. Introduction The unique catalytic properties of supported gold species were studied extensively during the past decades. The remarkable ability of these materials to catalyze different reactions at low temper- atures is attributed both to the presence of Au atoms with low coordination state on the surface of gold nanoparticles (Au NPs) and the mutual interaction of Au NPs and support [1–7]. The key role of gold-support interface in CO oxidation was clear shown exper- imentally for ceria in [8], where drastic improvement of catalytic activity of gold films was achieved by their decoration with ceria nanoparticles. It was definitely shown that the active sites for the CO oxidation on Au/CeO 2 are located at the interface of Au/CeO 2 . Similar effect of gold–ceria interface was found for CO oxidation reaction by the design of a set of ceria nanotower samples with the same surface area of Au and CeO 2 but different interfacial lengths [9]. Recent studies revealed that nanocrystalline CeO 2 used as sup- port increases the activity of gold species in CO oxidation by two orders of magnitude in comparison with conventional CeO 2 [10–13]. The activity of Au NPs deposited on ceria nanorods in CO ∗ Corresponding author. Tel.: +52 646 174 46 02x360; fax: +52 646 174 46 03. E-mail address: andrey@cnyn.unam.mx (A. Simakov). oxidation was higher than those supported on ceria nanoparticles [14]. It was established that not the crystallite size, but rather sur- face structure, more specifically the exposed surface planes of the crystalline CeO 2 support, is important for achieving a high redox and catalytic activity of Au NPs supported on ceria [14–17]. The strong effect of the crystal plane of ceria on the activity of gold species was confirmed for WGS reaction [18,19], low-temperature CO oxidation [14] and preferential CO oxidation [20,21]. Au NPs supported on {1 1 0} ceria planes presented as nanorods are more active in water gas shift (WGS) reaction than those sta- bilized on {1 0 0} ceria planes of nanoparticles or nanocubes [18]. At the present time, there are different techniques to prepare nanostructured ceria with different shape and size such as microwave assisted heating, flame spray pyrolysis, spray diffusion process, reverse micelles process/surfactant assisted, hydro- thermal treatment, sol–gel, chemical vapor deposition, thermal decomposition of cerium organo-metallic compounds, template directed synthesis, alcoholthermal treatment, nonisothermal pre- cipitation, etc. This wide set of techniques permits to fabricate ceria nanospecies in a shape of cubes, spheres, crystals, rods, wires, discs, plates, tubes, hollow spheres, pyramids, towers and flow- ers [9,18,19,22–24]. Among other techniques the hydrothermal treatment possesses extraordinary advantages of single step, low temperature, controlled composition and morphology, and high 0926-860X/$ – see front matter. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apcata.2012.09.045