Author's personal copy Short communication Direct coating of V 2 O 5 /TiO 2 nanoparticles onto glass beads by chemical vapor deposition Min Young Song a, b , Young-Kwon Park b, c, ⁎, Jongsoo Jurng a, ⁎⁎ a Center for Environment, Health and Welfare Research, Korea Institute of Science and Technology (KIST), 39‐1, Hawolgok, Seongbuk, Seoul 136‐791, Republic of Korea b Graduate School of Energy and Environmental System Engineering, University of Seoul, Seoul 130‐743, Republic of Korea c School of Environmental Engineering, University of Seoul, Seoul 130‐743, Republic of Korea abstract article info Article history: Received 22 March 2012 Received in revised form 11 June 2012 Accepted 21 July 2012 Available online 27 July 2012 Keywords: V 2 O 5 /TiO 2 nanocomposite CVD Single-step preparation Methylene blue V 2 O 5 /TiO 2 nanocomposite particles were synthesized and coated directly onto glass beads by chemical vapor deposition (CVD). Size-controlled, almost spherical, catalytic particles with agglomerated surface morphol- ogies were synthesized by controlling the gas flow rate. The CVD-coated glass beads had a more uniform nanoparticle coating than those prepared using a dip-coating method. The photocatalytic activities of the coated beads toward the degradation of aqueous methylene blue were tested and the best activity was exerted by the beads coated at a vanadium precursor gas flow rate of 1.0 L/min. The structures of the coated beads were examined by scanning electron microscopy, the Brunauer, Emmett and Teller surface area, X-ray diffraction and X-ray photoelectron spectroscopy. The CVD process was found to be a suitable method for the single-step preparation of nanocomposite coatings on glass bead supports. © 2012 Elsevier B.V. All rights reserved. 1. Introduction V 2 O 5 /TiO 2 is a catalyst commonly used in several industrially impor- tant reactions, including the selective oxidation of hydrocarbons [1–3], photocatalysis [4,5], and the selective reduction of NO x by NH 3 [6,7]. V 2 O 5 /TiO 2 shows excellent performance in slurry reactions [4,5], but it is difficult and expensive to separate the catalyst from the treated water. To overcome this, V 2 O 5 /TiO 2 powder has been immobilized or synthesized directly on a range of supports [8,9]. A wide variety of ma- terials including plates, honeycombs, fibers and beads have been used as supports for catalysts, with glass beads attracting considerable inter- est [5,6] owing to their favorable properties of thermal shock resistance, low pressure drop, chemical durability, high structural strength and low manufacturing cost. These materials can be used to remove toxic gasses and water pollutants. A range of methods for obtaining coatings well-adhered to glass bead supports has been developed, including chemical vapor deposition (CVD) [10], plasma spraying [11], dip-coating [12,13] and electrophoret- ic deposition (EPD) [14,15]. Dip-coating is the method most commonly used for coating powder catalysts onto supports. In this method, a finite thickness of catalysts is formed on the surface of the beads by repeated immersion into a slurry containing catalytic particles followed by drying and calcining [15,16]. Nevertheless, poor adhesion to the bead surface and non-uniform coatings are common. Controlling the thickness of the coatings is also difficult. CVD can be used to prepare catalysts with improved physicochemical properties, such as catalytic activity, hard- ness and mechanical stability, because it deposits catalytic nanoparticles onto bead supports. Additionally, different shaped metal or metal oxide supports can be coated uniformly using CVD. Moreover, this technique can be scaled-up and high throughput can be achieved with short pro- cessing times at relatively low cost when compared to other coating techniques [17]. Nasonova et al. [18] coated TiO 2 thin films onto glass beads using a rotating cylindrical plasma chemical vapor deposition (PCVD) reactor and analyzed the level of NO and SO 2 removal in a non-thermal plasma reactor packed with TiO 2 -coated glass beads. Kim et al. [19] deposited TiO 2 thin films onto hollow Pyrex glass beads during photocatalytic in- activation of algae in water. Jackson et al. [20] discussed methods for attaching TiO 2 to sodium borosilicate and aluminosilicate glasses, and examined the photoactivity of the resulting microbeads. Czok and Werther [21] coated glass beads with aluminum by CVD in a fluidized bed reactor at a range of temperatures. Several studies have examined coating monolithic beads using CVD [17–21], but there has been little work conducted to investigate the si- multaneous coating of beads and preparation of composite materials such as V 2 O 5 /TiO 2 . This study reports the use of CVD to coat catalytic V 2 O 5 /TiO 2 nanocomposites onto glass beads for the first time. The pro- cess enabled the single-step, simultaneous preparation of a composite catalyst and its coating to glass beads. The effect of the vanadium con- centration on the resulting structural characteristics of the particles was assessed by adjusting the flow rate of the vanadium precursor. Fi- nally, photocatalysis of methylene blue on the coated beads was Powder Technology 231 (2012) 135–140 ⁎ Correspondence to: Y.K. Park, Graduate School of Energy and Environmental Sys- tem Engineering, University of Seoul, Seoul 130‐743, Republic of Korea. Tel.: +82 2 2210 5623; fax: +82 2 2244 2245. ⁎⁎ Corresponding author. Tel.: +82 2 958 5688; fax: +82 2 958 6711. E-mail addresses: catalica@uos.ac.kr (Y.-K. Park), jongsoo@kist.kr (J. Jurng). 0032-5910/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.powtec.2012.07.043 Contents lists available at SciVerse ScienceDirect Powder Technology journal homepage: www.elsevier.com/locate/powtec