Facile synthesis of heterostructured Ag-deposited SiO2@TiO2 composite spheres with enhanced catalytic activity towards the photodegradation of AB 1 dyeby K.P.O. Mahesh, Dong-Hau Kuo, Bo-Rong Huang

Journal of Molecular Catalysis A: Chemical


Process Chemistry and Technology / Physical and Theoretical Chemistry / Catalysis


Journal of Molecular Catalysis A: Chemical 396 (2015) 290–296

Contents lists available at ScienceDirect

Journal of Molecular Catalysis A: Chemical jou rna l h om epa ge: www.elsev ier .com/ locate /molcata

Facile s ited compo tiv photod

K.P.O. Ma

Department of ogy, Ta a r t i c l

Article history:

Received 21 A

Received in re

Accepted 15 O

Available onlin


SiO2@TiO2 com

Ag nanoparticles


Dye degradation ed co lack ) we (iBuO phere g–SiO opy (X diffu spectroscopy (EIS). The photocatalytic activity of the Ag–SiO2@TiO2 photocatalyst towards AB 1 under

UV irradiation was studied. The effects of the operational parameters such as the different Ag contents on the SiO2@TiO2 composite spheres, as well as the effect of the initial concentration of the dye solution on photomineralization were analyzed. The results showed the Ag–SiO2@TiO2 photocatalyst to be efficient and reusable. 1. Introdu

Nowada lutants fou is estimate annum aro as industria cient remov remains an mental rem

Semicon widely used

Titanium d photocataly availability led to inten such as for p and lasers [ tion rate of ∗ Correspon

E-mail add http://dx.doi.o 1381-1169/© © 2014 Elsevier B.V. All rights reserved. ction ys, organic dyes are one of the foremost groups of polnd in wastewater produced by various industries. It d that roughly 700,000 tons of dyes are produced per und the world. Of this amount about 20% is unloaded l waste without prior action or treatment [1]. The effial of organic dye stuffs from industrially polluted water important and challenging issue in the field of environediation and pollution control. ductor-based heterogeneous photocatalysts have been to remove the dye stuffs in aqueous solutions [2–5]. ioxide is one of the most important semiconductor sts due to its high chemical stability, low cost, easy , and non-toxic nature, all of which have combined and se research attention and a broad range of applications hotocatalysts [6–9], sensors [10,11], solar cells [12,13], 14]. However, the large band gap and high recombinathe photogenerated electron–hole pairs tend to reduce ding author. Tel.: +886 2 27303291; fax: +886 2 27303291. ress: dhkuo@mail.ntust.edu.tw (D.-H. Kuo). the complete utilization of UV and solar energy. Also, it is very difficult to recover the TiO2 nanoparticles from a dye solution. In order to overcome these problems, the larger SiO2 particles have been used as a carrier/support for the dispersion of TiO2 nanoparticles on a surface. They can increase the active surface area of the TiO2 catalyst so as to facilitate the recycling process. Several studies have used the SiO2@TiO2 nanocomposite as a photocatalyst and reported a very good photocatalytic activity compared to the TiO2 catalyst.

The nano-sized SiO2 can not only be used as a substrate to absorb organic pollutants and to make contact with the active sites on

TiO2 particles, but also helps to disperse the very small sized TiO2 particles on the SiO2 surface [15–17].

To further limit the recombination of electron–hole pairs, inert metallic nanostructures such as Ag, Au, Pt or Pd have been deposited on the TiO2 nanoparticles in order to increase the life time of the electron–hole pairs [18–20]. Among these metal catalysts, Ag is one of the cheapest, most stable, and easily available, and also has the advantage that it can be easily deposited on the surface of

SiO2@TiO2 spheres. Zhao et al. and Xu et al. reported on the embedding of Ag nanoparticles on a SiO2/TiO2 film and confirmed that the Ag nanoparticles helped to enhance the photocatalytic activity of the SiO2/TiO2 film [21,22]. Chen et al. prepared SiO2/TiO2 nanocomposites by the solvothermal method and deposited Ag rg/10.1016/j.molcata.2014.10.017 2014 Elsevier B.V. All rights reserved.ynthesis of heterostructured Ag-depos site spheres with enhanced catalytic ac egradation of AB 1 dye hesh, Dong-Hau Kuo ∗, Bo-Rong Huang

Materials Science and Engineering, National Taiwan University of Science and Technol e i n f o pril 2014 vised form 15 October 2014 ctober 2014 e 24 October 2014 posite spheres a b s t r a c t

Ternary Ag–SiO2@TiO2 heterostructur lyst for the photodegradation of Acid B

SiO2@TiO2 composite spheres (320 nm tetraethyl orthosilicate (TEOS) and Ti were photodeposited on SiO2@TiO2 s the SiO2@TiO2 composite spheres (A (XRD), X-ray photoelectron spectrosc sion electron microscopy (TEM), UV- SiO2@TiO2 ity towards the ipei 10607, Taiwan mposite spheres were synthesized and investigated as a cata1 (AB 1) in an aqueous solution. The SiO2 spheres (310 nm) and re prepared without aggregation by the sol–gel method using )4 as precursors. Different concentrations of Ag nanoparticles s with particle sizes of about 10 nm. The Ag nanoparticles on 2@TiO2) were extensively characterized by X-ray diffraction

PS), field-emission scanning microscopy (FE-SEM), transmisse reflectance spectroscopy, and electrochemical impedance

K.P.O. Mahesh et al. / Journal of Molecular Catalysis A: Chemical 396 (2015) 290–296 291 nanoparticles in the form of Ag0 and Ag+ on the SiO2/TiO2 nanocomposites. They reported that the recombination of electron–hole pairs was inhibited by the deposition of Ag nanoparticles in the form of both Ag0 and Ag+ [23]. Mohamed and Mkhalid reported on the prep and impreg of catalysts et al. synthe propoxide a precursor [ sition on a specific wa

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TiO2 and re alytic activi the above s spheres wit nanoparticl

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Ag@SiO2@T enhanced v field of the hollow SiO method usi deposition visible light shell spher interlayer u surface fun alytic activ template an the Ag–SiO2 method to s formity of s

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Nano-sized face area. Th a soft temp the SiO2 cor form in size and field-e study the su photocataly 1) dye. 2. Experim 2.1. Materi