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Enhanced photocatalytic activity of C, F-codoped TiO2 loaded with AgCl

Enhanced photocatalytic activity of C, F-codoped TiO2 loaded with AgCl

Enhanced photocatalytic activity of C, F-codoped TiO2 loaded with AgCl

Enhanced photocatalytic activity of C,F-codoped TiO 2loaded with AgCl

Hongjian Yan a ,Saji Thomas Kochuveedu a ,Li Na Quan a ,Sang Soo Lee b ,Dong Ha Kim a ,?

a Department of Chemistry and Nano Science,College of Natural Sciences,Ewha Womans University,52,Ewhayeodae-gil,Seodaemun-gu,Seoul 120-750,Republic of Korea b

Polymer Hybrid Research Center,Korea Institute of Science and Technology,P.O.Box 131,Cheongryang,Seoul 130-650,Republic of Korea

a r t i c l e i n f o Article history:

Received 5November 2012

Received in revised form 20January 2013Accepted 21January 2013

Available online 13February 2013Keywords:

Co-doped TiO 2C,F-doping Photocatalysis

Visible light activity AgCl

a b s t r a c t

A protocol is reported for the development of a unique type of a co-doped TiO 2with two kinds of non-metal atoms,carbon (C)and ?uorine (F),as a visible-light active photocatalyst system.C,F-codoped TiO 2nanoobjects with anatase phase were synthesized by calcination of a mixture of TiOF 2and sulfuric-acid-treated melamine.The C,F co-doping resulted in a red-shift of the absorption edge to 510nm from the 390-nm value obtained for a control TiO 2photocatalyst.The C,F-codoped TiO 2shows photocatalytic activity under visible light irradiation.Furthermore,the loading of AgCl into the parent co-doped TiO 2enhanced its activity for degradation of methylene blue dye by about 3.5times in the ?rst hour irradiation.A brief mechanism responsible for the enhancement is proposed in terms of the transfer of holes from C,F-codoped TiO 2to the AgCl phase.

ó2013Elsevier B.V.All rights reserved.

1.Introduction

The photocatalytic puri?cation and treatment of water and air using semiconductor nanostructures and sunlight is an effective and promising technology for low-cost environmental remedia-tion.Titanium dioxide (TiO 2)is a most promising semiconductor that has been investigated substantially for its excellent optical and electronic properties,long-term stability,low cost,and non-toxicity [1–3].However,most as-prepared TiO 2is only responsive to ultraviolet (UV)light due to its relatively large band gap (3.2eV for anatase)hindering the utilization of visible light,which occu-pies ca.43%of the entire solar spectrum.

There are several methods to improve the photocatalytic perfor-mance of TiO 2:(1)Chemical doping of TiO 2with metallic (Cr,Fe,V)[4,5]or non-metallic (N,C,B,S or F)elements [6–11]to modify the electronic structures of semiconductors as well as their surface properties,thus extending their visible light absorbance.For exam-ple,C,W-codoped TiO 2exhibited higher visible-light photocata-lytic activity than undoped TiO 2,C-doped TiO 2or W-doped TiO 2.The co-doping of C and W not only leads to the narrowing of the band gap of TiO 2,but also increases the separation ef?ciency of the photo-generated electrons-hole pairs [11];(2)Synthesizing TiO 2with certain exposed facets,which is more reactive due to the higher average surface energy (demonstrated with both theo-retical and experimental evidence)[12–14].TiO 2with certain ex-posed facets has a substantial effect on the surface separation

and transfer of photogenerated electron–hole pairs,resulting in a signi?cant enhancement of photocatalytic ef?ciency;(3)Coupling with other semiconductors to increase the separation ef?ciency of photogenerated electron–hole pairs during photocatalysis [15–20].Recently,the composites comprising TiO 2and other semiconduc-tors,such as WO 3[21],Co 3O 4[22],SiC [15],and Fe 2O 3[16],have been reported.Among these methods,doping TiO 2with a non-me-tal element is a promising approach to achieving visible light re-sponse in TiO 2photocatalysts.Furthermore,doping with two kinds of non-metal atoms has shown more bene?cial effects.How-ever,representative combinations of two non-metal atoms have mostly focused on S/N,C/N,B/N,and N/F pairs [23–27].To the best of our knowledge,there have been few reports on the use of C and F as co-dopants.

Silver chloride (AgCl),which has a direct band gap of 5.6eV and an indirect band gap of 3.25eV,is widely recognized as a photo-sensitive material,and is employed as a source material in photo-graphic ?lms [28,29].Recently,a series of visible-light active composite photocatalysts containing silver halides have been developed for the degradation of organic pollutants [30–32].In these photocatalysts,both metallic Ag nanoparticles and silver ha-lides were generated,and it was revealed that the metallic compo-nent was responsible for the absorption of visible light and photocatalytic activity due to its surface plasmon resonance effect.Thus,it is a necessary and meaningful task to elucidate the role of Ag in the form of silver halides on the photocatalytic activity.

We report on a facile synthetic protocol of TiO 2co-doped with C and F elements via calcination of a mi
xture of TiOF 2and sulfuric-acid-treated melamine in Ar atmosphere.Further,we demonstrate that the C,F-codoped TiO 2shows enhanced absorption in the

We report on a facile synthetic protocol of TiO 2co-doped with C and F elements via calcination of a mixture of TiOF 2and sulfuric-acid-treated melamine in Ar atmosphere.Further,we demonstrate that the C,F-codoped TiO 2shows enhanced absorption in the

0925-8388/$-see front matter ó2013Elsevier B.V.All rights reserved.http://www.ffiun.com/doc/469d1d2052ea551810a687b7.html /10.1016/j.jallcom.2013.01.155

Corresponding author.Tel.:+82232774517;fax:+82232773419.

E-mail address:[email protected] (D.H.Kim).

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