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Large improvement of visible-light-driven photocatalytic property in AgCl nanoparticles modified black BiOCl microsphere
Materials Letters 127 (2014) 28–31
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Large improvement of visible-light-driven photocatalytic property in AgCl nanoparticles modified black BiOCl microsphere Jiushan Cheng, Cong Wang n, Yinfang Cui, Ying Sun, Ying Zuo, Tianming Wang Center for Condensed Matter and Material Physics, Department of Physics, Beihang University, Beijing 100191, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 15 February 2014 Accepted 6 April 2014 Available online 13 April 2014
In this paper, AgCl/BiOCl composite nanostructure has been synthesized by a facile ion exchange route between black BiOCl microsphere and AgNO3 solution. The as-obtain products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). Photodegradation experiments show that the photocatalytic activity of AgCl/BiOCl composite nanostructure is improved greatly by composited AgCl nanoparticles, compared with pure black BiOCl microsphere. The excellent photocatalytic activity of AgCl/BiOCl composite nanostructure with special surface morphology may be attributed to decreasing recombination of the photo-excited electron–hole pairs. In addition, AgCl/BiOCl composite possesses strong absorption to visible light which can also improve the photocatalytic efficiency. & 2014 Elsevier B.V. All rights reserved.
Keywords: AgCl/BiOCl Photocatalyst Semiconductors Nanocomposites Visible- light-driven
1. Introduction BiOCl has been widely applied in the fields of catalysis [1], photoluminescence materials [2], ferroelectric materials [3] and pigments [4] for many years owing to its unique layered structure and high photocorrosion stability [5]. Furthermore, BiOCl has also been well-known as effectual photocatalyst for decomposing organic compounds in polluted wastewater [6]. BiOCl is a layered compound, which consists of [Bi2O2]2 þ layers sandwiched between two sheets of Cl ions [7]. The unique layered structure of BiOCl results in the general formation of plate morphology, which facilitates the deposition of inorganic nanomaterials. However, BiOCl still faces the same challenges alike the most of photocatalysts, which are limited by light absorption, large energy loss, and the rapid recombination of photogenerated charge carriers [8]. It is suggested that BiOCl series visible light photocatalysts by compositing with other semiconductors materials can solve the problem. Recently, to pursue higher photocatalytic activity, several kinds of BiOCl inorganic nanocomposites have been reported, such as, BiOCl/ TiO2 [9], BiOCl/Bi2S3 [10], etc. In addition, many works have demonstrated that AgX (X¼Cl, Br, I) were much efficient and stable photocatalysts under visible light illumination [11]. Due to its photosensitive characteristic, AgX have often been performed as sensitizer to enhance the photocatalytic activity of UV-responding semiconductors under visible light irradiation [12]. The plasmonic photocatalysts
n
Corresponding author. Tel./fax: þ 86 10 82338346. E-mail address: [email protected] (C. Wang).
http://dx.doi.org/10.1016/j.matlet.2014.04.012 0167-577X/& 2014 Elsevier B.V. All rights reserved.
Ag/AgBr/BiOBr were first reported by Huang's group [13,14]. However, to our knowledge, nobody reported the photocatalytic activity of AgCl/ BiOCl composite nanostructure. In this paper, we successfully prepared AgCl nanoparticles modified BiOCl microsphere through a simple hydrothermal route combining with the following ion-exchange of AgNO3 in an aqueous system. Photocatalytic degradation experiments show that AgCl/BiOCl composite possesses strong degradation capacity for organic dye, and the photocatalytic properties are improved largely compared with pure BiOCl.
2. Experimental All the reagents were analytically pure. Detailed experimental synthesis process, characterization methods and the photocatalytic test system were given in the Supporting information.
3. Results and discussion The crystal structures of BiOCl before and after compositing AgCl have been analyzed by XRD as shown in Fig. 1. All the diffraction peaks can be indexed to the pure BiOCl with the tetragonal phase (JCPDS card no. 06-0249). When putting AgCl as the composite, there are two new diffraction peaks of AgCl (JCPDS card no. 31-1238) at 2θ E271 and 471 appearing. The XRD result of AgCl/BiOCl before and after photocatalytic degradation shows that no other new phase or impurity peak is detected.
J. Cheng et al. / Materials Letters 127 (2014) 28–31
The morphologies of the pure BiOCl and AgCl/BiOCl composite are observed by SEM. Fig. 2a exhibits a representative SEM image of pure BiOCl with an average diameter of 3 μm. The highly monodispersed rough ball-like spheres are obtained whose preparing method has been described elsewhere [15]. The microsphere is composed of thin plates as shown in the inset of Fig. 2a. The nanoplates with the thickness of about 40 nm align radically and tightly to assemble into the uniform spheres. After pure BiOCl ball-like
Fig. 1. XRD patterns of BiOCl and AgCl/BiOCl.
29
spheres are immersed into AgNO3 solution, SEM (Fig. 2b) observation shows that some cubic nanoparticles with various sizes strew on the sphere. TEM image (Fig. 2c) shows the existence of AgCl particles from the morphology of the products. The lattice stripe with d¼0.32 nm implies the (111) plane of the cubic AgCl (JCPDS 31-1238), suggesting that the AgCl particles exist on the surface of BiOCl microsphere (see the insets shown in Fig. 2c). Fig. 2d shows a typical EDX spectrum obtained from the AgCl/BiOCl composite. The signals of Bi, O, Ag, and Cl are observed in the spectrum. Quantitative analysis indicates a composition of AgCl, as the nanoparticles attached on the surface of the BiOCl microsphere. UV vis diffuse reflectance spectra of as-prepared BiOCl and AgCl/BiOCl composite are shown in Fig. 3a. In compare with the pure BiOCl, the absorption during visible light range of AgCl/BiOCl composite is much improved. The XPS is used to determine the chemical composition and the valence states of the prepared species. The Ag element of the AgCl/BiOCl composite is characterized by XPS spectra (Fig. 3b). As can be seen, both the Ag 3d core spectra exhibit narrow Gauss-shaped symmetry. It consists of two individual peaks at approximately 373.42 eV and 367.42 eV, which are ascribed to the peaks of Ag 3d3/2 and Ag 3d5/2, respectively. It is attributed to Ag þ from AgCl, and no metallic Ag is detected [16]. In Fig. 4a, it is notable that the photolysis of MO without photocatalyst can be neglected. From the curves of the concentration changes of MO dye, we can see that about 90% is degraded by the AgCl/BiOCl composite only in 8 min, but pure BiOCl and AgCl about 70% and 80% of MO dye, respectively, under visible irradiation for 70 min. From the TOC result shown in Fig. 4a, we can see the MO is really degraded by BiOCl/AgCl photocatalysis. The inset of Fig. 4a shows the change of the light absorption spectra of the MO dye with the irradiation time, from which we obtain the
Fig. 2. SEM images of (a) BiOCl; (b) AgCl/BiOCl; (c) TEM image of AgCl/BiOCl, the inset shows HRTEM of AgCl nanoparticles; (d) corresponding EDS pattern of AgCl/BiOCl.
30
J. Cheng et al. / Materials Letters 127 (2014) 28–31
Fig. 3. (a) DRS spectra of AgCl/BiOCl and BiOCl; (b) XPS spectra of Ag 3d of AgCl/BiOCl.
Fig. 4. (a) Photocatalytic degradation efficiencies of MO over AgCl/BiOCl, AgCl and BiOCl, TOC of MO during the photocatalytic degradation of MO in the presence of AgCl/BiOCl, the inset shows UV–vis absorption spectral changes of MO over AgCl/BiOCl at given time intervals; (b) cycling tests of MO degradation over AgCl/BiOCl.
degradation curves. According to the photocatalytic activity of all the samples, the AgCl/BiOCl composite greatly improves the photocatalytic activity, compared with AgCl or BiOCl. Fig. 4b shows the recycling properties of AgCl/BiOCl composite for MO dye under visible light irradiation. The figure shows that the degraded rate of MO is not significantly decreased even after 3 cycles, indicating the high activity and stability of the AgCl/BiOCl photocatalysis. We have reported [17,18] the BiOCl flakes and nanowire arrays. Recently, we have synthesized the BiOCl microspheres which degraded 70% of MO dye in 70 min. In order to improve the photocatalytic property of BiOCl, we choose AgCl to be composited with BiOCl. Obviously, AgCl/BiOCl composite possesses stronger photocatalytic capacity for the degradation of MO. According to some reports [19], we deduce that AgCl and BiOCl have matching band potential, because that the valence band (VB) edge of BiOCl (3.55 eV) is more positive than that of AgCl (3.16 eV), while the conduction band (CB) edge of AgCl ( 0.09 eV) is more negative than that of BiOCl (0.11 eV). The band potentials of both AgCl and BiOCl semiconductors are conductive to prevent the recombination of electrons and holes in the AgCl/BiOCl composite [20]. At the same time, the photo-generated electrons (e )
are transferred from AgCl to BiOCl, holding back its coupling with some Ag þ to form metallic Ag, which also implies the stability of AgCl [21]. In general, the AgCl/BiOCl composite with special nanostructure and interface increases the visible-light absorption and restrains the recombination of electron–hole pairs. At first, the existence of AgCl nanocrystals on the surfaces of the BiOCl microspheres forms unique nanostructure, which provides a high surface area and a large number of interfaces. From Niyong Hong's reports [22], AgBr nanoparticles modified BiOBr nanoplates exhibited superior photocatalytic property owning to its special microstructure. Second, the absorption of the AgCl/BiOCl composite to the visible-light is increased, compared with pure BiOCl. Third, the effective charge transfer in the interface of AgCl/BiOCl composite makes sure the separation of electron–hole pairs. All the facts make the composite display excellent photocatalytic property.
4. Conclusion In summary, a simple hydrothermal technique combined with a special ion-exchange route has been developed to synthesize
J. Cheng et al. / Materials Letters 127 (2014) 28–31
AgCl/BiOCl composite nanostructure. The nanostructure consists of some cubic AgCl nanoparticles with various sizes strew on the black BiOCl microsphere with an average diameter of 3 μm. The AgCl/BiOCl composite nanostructure can degrade 90% of MO dye in 8 min, but pure black BiOCl microsphere only degrade 70% of MO dye in 70 min. The result shows that AgCl/BiOCl composite nanostructure displays highly efficient photocatalytic activities. Acknowledgments This work was supported by the National Natural Science Foundation of China (51172012 and 51272015). Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2014.04. 012. References [1] Lopez-Salinas FI, Martinez-Castanon GA, Martinez-Mendoza JR, Ruiz F. Mater Lett 2010;64:1555–8. [2] Deng ZT, Tang FQ, Muscat AJ. Nanotechnology 2008;19:295705. [3] Kusainova AM, Lightfoot P, Zhou WZ, Stefanovich SY, Mosunov AV, Dolgikh VA. Chem Mater 2001;13:4731–7.
31
[4] Maile FJ, Pfaff G, Reynders P. Prog Org Coat 2005;54:150–63. [5] Shamaila S, Sajjad AKL, Chen F, Zhang JL. J Colloid Interface Sci 2011;356: 465–72. [6] Lin XP, Huang T, Huang FQ, Wang WD, Shi JL. J. Phys Chem B 2006;110: 24629–34. [7] Liu YY, Son WJ, Lu JB, Huang BB, Dai Y, Whangbo MH. Chemistry 2011;17: 9342–9. [8] Chai SY, Kim YJ, Jung MH, Chakraborty AK, Jung JW, Lee WI. J Catal 2009;262: 144–9. [9] Zhang X, Zhang LZ, Xie TF, Wang DJ. J Phys Chem C 2009;113:7371–8. [10] Cheng HF, Huang BB, Qin XY, Zhang XY, Dai Y. Chem Commun 2012;48:97–9. [11] Zang YJ, Farnood R. Appl Catal B 2008;79:334–40. [12] Yan TJ, Yan XY, Guo RR, Zhang WN, Li WJ, You JM. Catal Commun 2013;42: 30–4. [13] Wang P, Huang BB, Qin XY, Zhang XY, Dai Y, Wei JY, et al. Angew Chem Int Ed 2008;47:7931–3. [14] Wang P, Huang BB, Zhang XY, Qin XY, Jin H, Dai Y, et al. Chemistry 2009;15: 1821–4. [15] Li JF, Zhu YC, Yan Y, Xi BJ, Tang KB, Qian YT. J Nanosci Nano Technol 2012;12: 2068–75. [16] Bai J, Li YX, Li MY, Wang SG, Zhang CQ, Yang QB. Appl Surf Sci 2008;254: 4520–3. [17] Wu SJ, Wang C, Cui YF, Hao WC, Wang TM, Brault P. Mater Lett 2011;65: 1344–7. [18] Wu SJ, Wang C, Cui YF, Wang TM, Huang BB, Zhang XY, et al. Mater Lett 2010; 64:115–8. [19] Bassani F, Knox RS, Beall Fowler W. Phys Rev 1965;137:1217–25. [20] Cheng HF, Huang BB, Wang P, Wang ZY, Lou ZZ, Wang JP, et al. Chem Commun 2011;47:7054–6. [21] Cheng HF, Wang WJ, Huang BB, Wang ZY, Zhan J, Qin XY, et al. Mater Chem A 2013;1:7131–46. [22] Cheng C, Ni YH, Ma X, Hong JM. Mater Lett 2012;79:273–6.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Large improvement of visible-light-driven photocatalytic property in AgCl nanoparticles modified black BiOCl microsphere Jiushan Cheng, Cong Wang n, Yinfang Cui, Ying Sun, Ying Zuo, Tianming Wang Center for Condensed Matter and Material Physics, Department of Physics, Beihang University, Beijing 100191, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 15 February 2014 Accepted 6 April 2014 Available online 13 April 2014
In this paper, AgCl/BiOCl composite nanostructure has been synthesized by a facile ion exchange route between black BiOCl microsphere and AgNO3 solution. The as-obtain products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). Photodegradation experiments show that the photocatalytic activity of AgCl/BiOCl composite nanostructure is improved greatly by composited AgCl nanoparticles, compared with pure black BiOCl microsphere. The excellent photocatalytic activity of AgCl/BiOCl composite nanostructure with special surface morphology may be attributed to decreasing recombination of the photo-excited electron–hole pairs. In addition, AgCl/BiOCl composite possesses strong absorption to visible light which can also improve the photocatalytic efficiency. & 2014 Elsevier B.V. All rights reserved.
Keywords: AgCl/BiOCl Photocatalyst Semiconductors Nanocomposites Visible- light-driven
1. Introduction BiOCl has been widely applied in the fields of catalysis [1], photoluminescence materials [2], ferroelectric materials [3] and pigments [4] for many years owing to its unique layered structure and high photocorrosion stability [5]. Furthermore, BiOCl has also been well-known as effectual photocatalyst for decomposing organic compounds in polluted wastewater [6]. BiOCl is a layered compound, which consists of [Bi2O2]2 þ layers sandwiched between two sheets of Cl ions [7]. The unique layered structure of BiOCl results in the general formation of plate morphology, which facilitates the deposition of inorganic nanomaterials. However, BiOCl still faces the same challenges alike the most of photocatalysts, which are limited by light absorption, large energy loss, and the rapid recombination of photogenerated charge carriers [8]. It is suggested that BiOCl series visible light photocatalysts by compositing with other semiconductors materials can solve the problem. Recently, to pursue higher photocatalytic activity, several kinds of BiOCl inorganic nanocomposites have been reported, such as, BiOCl/ TiO2 [9], BiOCl/Bi2S3 [10], etc. In addition, many works have demonstrated that AgX (X¼Cl, Br, I) were much efficient and stable photocatalysts under visible light illumination [11]. Due to its photosensitive characteristic, AgX have often been performed as sensitizer to enhance the photocatalytic activity of UV-responding semiconductors under visible light irradiation [12]. The plasmonic photocatalysts
n
Corresponding author. Tel./fax: þ 86 10 82338346. E-mail address: [email protected] (C. Wang).
http://dx.doi.org/10.1016/j.matlet.2014.04.012 0167-577X/& 2014 Elsevier B.V. All rights reserved.
Ag/AgBr/BiOBr were first reported by Huang's group [13,14]. However, to our knowledge, nobody reported the photocatalytic activity of AgCl/ BiOCl composite nanostructure. In this paper, we successfully prepared AgCl nanoparticles modified BiOCl microsphere through a simple hydrothermal route combining with the following ion-exchange of AgNO3 in an aqueous system. Photocatalytic degradation experiments show that AgCl/BiOCl composite possesses strong degradation capacity for organic dye, and the photocatalytic properties are improved largely compared with pure BiOCl.
2. Experimental All the reagents were analytically pure. Detailed experimental synthesis process, characterization methods and the photocatalytic test system were given in the Supporting information.
3. Results and discussion The crystal structures of BiOCl before and after compositing AgCl have been analyzed by XRD as shown in Fig. 1. All the diffraction peaks can be indexed to the pure BiOCl with the tetragonal phase (JCPDS card no. 06-0249). When putting AgCl as the composite, there are two new diffraction peaks of AgCl (JCPDS card no. 31-1238) at 2θ E271 and 471 appearing. The XRD result of AgCl/BiOCl before and after photocatalytic degradation shows that no other new phase or impurity peak is detected.
J. Cheng et al. / Materials Letters 127 (2014) 28–31
The morphologies of the pure BiOCl and AgCl/BiOCl composite are observed by SEM. Fig. 2a exhibits a representative SEM image of pure BiOCl with an average diameter of 3 μm. The highly monodispersed rough ball-like spheres are obtained whose preparing method has been described elsewhere [15]. The microsphere is composed of thin plates as shown in the inset of Fig. 2a. The nanoplates with the thickness of about 40 nm align radically and tightly to assemble into the uniform spheres. After pure BiOCl ball-like
Fig. 1. XRD patterns of BiOCl and AgCl/BiOCl.
29
spheres are immersed into AgNO3 solution, SEM (Fig. 2b) observation shows that some cubic nanoparticles with various sizes strew on the sphere. TEM image (Fig. 2c) shows the existence of AgCl particles from the morphology of the products. The lattice stripe with d¼0.32 nm implies the (111) plane of the cubic AgCl (JCPDS 31-1238), suggesting that the AgCl particles exist on the surface of BiOCl microsphere (see the insets shown in Fig. 2c). Fig. 2d shows a typical EDX spectrum obtained from the AgCl/BiOCl composite. The signals of Bi, O, Ag, and Cl are observed in the spectrum. Quantitative analysis indicates a composition of AgCl, as the nanoparticles attached on the surface of the BiOCl microsphere. UV vis diffuse reflectance spectra of as-prepared BiOCl and AgCl/BiOCl composite are shown in Fig. 3a. In compare with the pure BiOCl, the absorption during visible light range of AgCl/BiOCl composite is much improved. The XPS is used to determine the chemical composition and the valence states of the prepared species. The Ag element of the AgCl/BiOCl composite is characterized by XPS spectra (Fig. 3b). As can be seen, both the Ag 3d core spectra exhibit narrow Gauss-shaped symmetry. It consists of two individual peaks at approximately 373.42 eV and 367.42 eV, which are ascribed to the peaks of Ag 3d3/2 and Ag 3d5/2, respectively. It is attributed to Ag þ from AgCl, and no metallic Ag is detected [16]. In Fig. 4a, it is notable that the photolysis of MO without photocatalyst can be neglected. From the curves of the concentration changes of MO dye, we can see that about 90% is degraded by the AgCl/BiOCl composite only in 8 min, but pure BiOCl and AgCl about 70% and 80% of MO dye, respectively, under visible irradiation for 70 min. From the TOC result shown in Fig. 4a, we can see the MO is really degraded by BiOCl/AgCl photocatalysis. The inset of Fig. 4a shows the change of the light absorption spectra of the MO dye with the irradiation time, from which we obtain the
Fig. 2. SEM images of (a) BiOCl; (b) AgCl/BiOCl; (c) TEM image of AgCl/BiOCl, the inset shows HRTEM of AgCl nanoparticles; (d) corresponding EDS pattern of AgCl/BiOCl.
30
J. Cheng et al. / Materials Letters 127 (2014) 28–31
Fig. 3. (a) DRS spectra of AgCl/BiOCl and BiOCl; (b) XPS spectra of Ag 3d of AgCl/BiOCl.
Fig. 4. (a) Photocatalytic degradation efficiencies of MO over AgCl/BiOCl, AgCl and BiOCl, TOC of MO during the photocatalytic degradation of MO in the presence of AgCl/BiOCl, the inset shows UV–vis absorption spectral changes of MO over AgCl/BiOCl at given time intervals; (b) cycling tests of MO degradation over AgCl/BiOCl.
degradation curves. According to the photocatalytic activity of all the samples, the AgCl/BiOCl composite greatly improves the photocatalytic activity, compared with AgCl or BiOCl. Fig. 4b shows the recycling properties of AgCl/BiOCl composite for MO dye under visible light irradiation. The figure shows that the degraded rate of MO is not significantly decreased even after 3 cycles, indicating the high activity and stability of the AgCl/BiOCl photocatalysis. We have reported [17,18] the BiOCl flakes and nanowire arrays. Recently, we have synthesized the BiOCl microspheres which degraded 70% of MO dye in 70 min. In order to improve the photocatalytic property of BiOCl, we choose AgCl to be composited with BiOCl. Obviously, AgCl/BiOCl composite possesses stronger photocatalytic capacity for the degradation of MO. According to some reports [19], we deduce that AgCl and BiOCl have matching band potential, because that the valence band (VB) edge of BiOCl (3.55 eV) is more positive than that of AgCl (3.16 eV), while the conduction band (CB) edge of AgCl ( 0.09 eV) is more negative than that of BiOCl (0.11 eV). The band potentials of both AgCl and BiOCl semiconductors are conductive to prevent the recombination of electrons and holes in the AgCl/BiOCl composite [20]. At the same time, the photo-generated electrons (e )
are transferred from AgCl to BiOCl, holding back its coupling with some Ag þ to form metallic Ag, which also implies the stability of AgCl [21]. In general, the AgCl/BiOCl composite with special nanostructure and interface increases the visible-light absorption and restrains the recombination of electron–hole pairs. At first, the existence of AgCl nanocrystals on the surfaces of the BiOCl microspheres forms unique nanostructure, which provides a high surface area and a large number of interfaces. From Niyong Hong's reports [22], AgBr nanoparticles modified BiOBr nanoplates exhibited superior photocatalytic property owning to its special microstructure. Second, the absorption of the AgCl/BiOCl composite to the visible-light is increased, compared with pure BiOCl. Third, the effective charge transfer in the interface of AgCl/BiOCl composite makes sure the separation of electron–hole pairs. All the facts make the composite display excellent photocatalytic property.
4. Conclusion In summary, a simple hydrothermal technique combined with a special ion-exchange route has been developed to synthesize
J. Cheng et al. / Materials Letters 127 (2014) 28–31
AgCl/BiOCl composite nanostructure. The nanostructure consists of some cubic AgCl nanoparticles with various sizes strew on the black BiOCl microsphere with an average diameter of 3 μm. The AgCl/BiOCl composite nanostructure can degrade 90% of MO dye in 8 min, but pure black BiOCl microsphere only degrade 70% of MO dye in 70 min. The result shows that AgCl/BiOCl composite nanostructure displays highly efficient photocatalytic activities. Acknowledgments This work was supported by the National Natural Science Foundation of China (51172012 and 51272015). Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2014.04. 012. References [1] Lopez-Salinas FI, Martinez-Castanon GA, Martinez-Mendoza JR, Ruiz F. Mater Lett 2010;64:1555–8. [2] Deng ZT, Tang FQ, Muscat AJ. Nanotechnology 2008;19:295705. [3] Kusainova AM, Lightfoot P, Zhou WZ, Stefanovich SY, Mosunov AV, Dolgikh VA. Chem Mater 2001;13:4731–7.
31
[4] Maile FJ, Pfaff G, Reynders P. Prog Org Coat 2005;54:150–63. [5] Shamaila S, Sajjad AKL, Chen F, Zhang JL. J Colloid Interface Sci 2011;356: 465–72. [6] Lin XP, Huang T, Huang FQ, Wang WD, Shi JL. J. Phys Chem B 2006;110: 24629–34. [7] Liu YY, Son WJ, Lu JB, Huang BB, Dai Y, Whangbo MH. Chemistry 2011;17: 9342–9. [8] Chai SY, Kim YJ, Jung MH, Chakraborty AK, Jung JW, Lee WI. J Catal 2009;262: 144–9. [9] Zhang X, Zhang LZ, Xie TF, Wang DJ. J Phys Chem C 2009;113:7371–8. [10] Cheng HF, Huang BB, Qin XY, Zhang XY, Dai Y. Chem Commun 2012;48:97–9. [11] Zang YJ, Farnood R. Appl Catal B 2008;79:334–40. [12] Yan TJ, Yan XY, Guo RR, Zhang WN, Li WJ, You JM. Catal Commun 2013;42: 30–4. [13] Wang P, Huang BB, Qin XY, Zhang XY, Dai Y, Wei JY, et al. Angew Chem Int Ed 2008;47:7931–3. [14] Wang P, Huang BB, Zhang XY, Qin XY, Jin H, Dai Y, et al. Chemistry 2009;15: 1821–4. [15] Li JF, Zhu YC, Yan Y, Xi BJ, Tang KB, Qian YT. J Nanosci Nano Technol 2012;12: 2068–75. [16] Bai J, Li YX, Li MY, Wang SG, Zhang CQ, Yang QB. Appl Surf Sci 2008;254: 4520–3. [17] Wu SJ, Wang C, Cui YF, Hao WC, Wang TM, Brault P. Mater Lett 2011;65: 1344–7. [18] Wu SJ, Wang C, Cui YF, Wang TM, Huang BB, Zhang XY, et al. Mater Lett 2010; 64:115–8. [19] Bassani F, Knox RS, Beall Fowler W. Phys Rev 1965;137:1217–25. [20] Cheng HF, Huang BB, Wang P, Wang ZY, Lou ZZ, Wang JP, et al. Chem Commun 2011;47:7054–6. [21] Cheng HF, Wang WJ, Huang BB, Wang ZY, Zhan J, Qin XY, et al. Mater Chem A 2013;1:7131–46. [22] Cheng C, Ni YH, Ma X, Hong JM. Mater Lett 2012;79:273–6.