- Email: [email protected]
SBA-15 composites prepared using H2TiO3 by hydrothermal method and its photocatalytic activity
Materials Letters 99 (2013) 38–41
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
TiO2/SBA-15 composites prepared using H2TiO3 by hydrothermal method and its photocatalytic activity Xiao-jing Wang, Fa-tang Li n, Ying-juan Hao, Shuang-jun Liu, Min-li Yang College of Science, Hebei University of Science and Technology, Shijiazhuang 050018, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 September 2012 Accepted 14 February 2013 Available online 21 February 2013
A novel approach of SBA-15 mesoporous materials decorated with various amounts of TiO2 (10–30% TiO2/SBA-15) were prepared by the post-synthesis method using metatitanic acid as precursor and template-retentive SBA-15 as support. The result shows that the silica framework was stable and it was almost not affected by appropriate titania deposition. The photocatalytic activity of the samples was tested by degradation of methyl orange (MO), which was increased with increasing TiO2 loading ratio at first and then decreased. The 17% TiO2/SBA-15 composite calcinated at 600 1C showed the highest photocatalytic ability for degradation of MO because of its appropriate amount of TiO2 and less agglomeration. & 2013 Elsevier B.V. All rights reserved.
Keywords: Nanocomposites Semiconductors Metatitanic acid TiO2 SBA-15 Photocatalysis
1. Introduction TiO2 has been considered as one of the most promising photocatalysts because of its nontoxicity, photo- and chemicalstability, low cost, and superior photocatalytic activity [1]. However, its applications are hindered by two disadvantages. Firstly, small particles tend to agglomerate into large ones, making against on catalyst performance. Secondly, TiO2 nanoparticles less than 20 nm in diameter are very active photocatalysts but such nanoparticles are somewhat impractical for industrial applications because downstream nanoparticles recycling processes are difficult [2,3]. On this basis, great efforts have been focused on developing supported titania catalysts offering high dispersed properties and easy reusing size for TiO2 [2,4]. Ordered Mesoporous Silicas (OMSs) such as SBA-15 are widely used as catalytic supports, which have high thermal and chemical stability, as well as tunable surface composition and pore size [5–7]. However, most of the reported works are mainly based on sol–gel processing using titanium alkoxides and titanium tetrachloride as the titanium sources [8–10]. The former is expensive and the latter contains chlorine, which would bring problem of environmental pollution. Therefore, it is necessary to find an inexpensive and environment-friendly reagent to prepare composite TiO2 photocatalysts. Besides, in lot of researches, the template-free supports were used. Shao et al. [11] and Zhang et al. [12] found that when template-free SBA-15 was used as a support, the dispersion
n
Corresponding author. Tel.: þ86 311 8166 9971; fax: þ 86 311 8166 8528. E-mail address: [email protected] (F.-t. Li).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.02.060
amount of anchored species was relatively low, and the particles of active species were easy to aggregate. However, less attention has been paid to the as-prepared SBA-15 materials containing template as support. In this work, a novel approach to synthesize TiO2/SBA-15 materials by using metatitanic acid as titanium source and SBA15 materials containing template as support was proposed. This strategy is not only a low cost technique, but also allows high dispersion of TiO2. It would help to improve the mesostructural stability and long-range order of the adsorbents. Its photocatalytic activity for decomposition of MO was also investigated.
2. Experiments Siliceous SBA-15 mesoporous material was synthesized according to the procedure described by Zhao et al. [13]. The Pluronic triblock copolymer P123 (BASF) was used as the structure-directing agent and tetraethylorthosilicate (TEOS) as a source of silica. In a typical synthesis, the triblock copolymer was dissolved in a mixture of deionized water and 4 M hydrochloric acid solution stirred for 1 h, after which the required amount of TEOS was added to the solution at 308 K and kept under stirring conditions for 24 h. After synthesis, the obtained solid was filtered, washed with ice distilled water and dried at room temperature in air, and the obtained white powder was asprepared SBA-15. To prepare peroxotitanate, different amounts of H2TiO3 was added into an ice-cooled solution containing H2O, H2O2 (30%) and NH4OH (28%). After being stirred for 60 min, a homogeneous pale
X.-j. Wang et al. / Materials Letters 99 (2013) 38–41
yellow-green solution was obtained and then adjusted to pH¼7 by HNO3 (2 M). Then, given amount of as-prepared SBA-15 was added in the solution. After stirring for 5 h, the samples were transferred into a Teflon reactor of 50 mL inside a stainless-steel vessel and heated at 160 1C for 6 h. After the hydrothermal treatment, the products were separated by filtration and then dried 60 1C. The samples were calcined at 400–700 1C for 2 h to obtain final TiO2/SBA-15 composites. For comparison, pure TiO2 powder was also prepared through the same procedure and calcined at 600 1C, but without SBA-15 addition. The photocatalytic experiments were carried out in a 500 mL cylindrical glass reactor inside equipped with a high-pressure mercury lamp using 300 ml MO solution with an initial concentration of 50 mg/L and 0.4 g catalyst. The concentration of MO was determined by spectroscopic analysis at 464 nm. X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) were obtained on a Bruker D8-Advance X-ray diffractometer using CuKa radiation. Transmission electron microscopy
39
(TEM) images were taken with a JEOL JEM-2010 electron microscope. Nitrogen adsorption isotherms for the SBA-15 samples were collected by Quantachrome Nova 2000 instrument. Fourier transform infrared (FT-IR) spectra were obtained using a Shimadzu IR Prestige 21 spectrometer.
3. Results and discussion Table S1 shows the textural properties of the siliceous SBA-15 and TiO2/SBA-15 samples calcinated at 600 1C. It is clear that loading TiO2 on the silica matrix slightly decreases the surface area, pore volume, and pore size of the support, which indicates that most of the TiO2 particles are not loaded within the ordered channels of the support. The structure formation process is proposed as Scheme 1. Fig. 1a shows the XRD patterns of 17% TiO2/SBA-15 materials treated at different temperature. These patterns matched well
calcine
mix peroxotitanate
P123
silica
peroxotitanat
TiO
10
20
30
40
50
2 Theta (°)
60
70
Intensity (a.u)
Intensity (a.u)
Intensity (a.u)
Scheme 1. Schematic diagram of preparation process on TiO2/SBA-15 samples.
10
20
30
40
50
60
70
2 Theta (°)
1
2
3
4
5
2 Theta (°)
Fig. 1. XRD patterns of (a) 17% TiO2/SBA-15 with different calcination temperatures, (b) x% TiO2/SBA-15 calcined at 600 1C, and (c) small-angle XRD patterns of the SBA-15 and 17% TiO2/SBA-15.
Fig. 2. TEM images of 17% TiO2/SBA-15 material.
40
X.-j. Wang et al. / Materials Letters 99 (2013) 38–41
with the standard pattern of anatase TiO2 (JCPDS 21-1272). With the increase of calcination temperature, the peaks of anatase become narrower and higher, implying the growth of TiO2 crystal. The average crystalline sizes are 8.9 nm, 9.5 nm, 12.7 nm and 14.5 nm from 400–700 1C, calculated from the most intense diffraction peak (101) corresponding to peak at 2y ¼25.31 using Scherer equation. Furthermore, the TiO2/SBA-15 calcinated at 700 1C retains the structure of anatase and no rutile peak is found, suggesting that the TiO2/SBA-15 has high thermal stability because of a stabilizing effect of silica on the anatase–rutile transition at higher temperatures [3,14] and the hindrance of interfacial energy between TiO2 and SBA-15. Wide-angle XRD patterns of the mesoporous x% TiO2/SBA-15 samples calcined at 600 1C were also recorded (shown in Fig.1b). It can be seen that the intensity of the (101) diffraction peak becomes higher with the increase of TiO2 content. Fig. 1c shows the small-angle XRD patterns of the SBA-15 and 17% TiO2/SBA-15 materials calcinated at 600 1C. The calcined SBA-15 sample displayed a well-resolved pattern with a sharp peak at about 1.01 which was consistent with the reported pattern [7]. In the case of the samples with a loading of titanium dioxide, the XRD patterns, especially the order Bragg reflections and the XRD peaks are not broadened, suggesting that the silica framework was stable and it was not affected by titania deposition. However, compared with SBA-15, the primary diffraction peak of 17% TiO2/SBA-15 shift to higher angles, which
SBA-15
Transmittance (a.u)
971
17% TiO2/SBA-15
indicates the slightly deposition of TiO2 in the mesopores [15]. These results are consistent with the BET results. Fig. 2a and b shows the TEM images of the 17% TiO2/SBA-15 sample. A well-ordered hexagonal array of mesopores can be seen when the electron beam is parallel to the main axis of the cylindrical pores. When the electron beam is perpendicular to the main axis, the presence of the parallel nanotubular pores in the parent SBA-15 matrix is evidenced. The introduction of titanium does not substantially alter the regular ordered structure of the mesopores, which is consistent with SAXS and BET results. The FT-IR spectra of the SBA-15 and 17% TiO2/SBA-15 calcinated at 600 1C are shown in Fig. 3. For parent SBA-15 silica, a weak band at about 971 cm 1 is attributed to the Si–OH stretching vibration [16]. After combining with TiO2, a small shift of about 7 cm 1 to lower frequencies is observed, showing that the incorporated TiO2 particles have been structurally combined with SiO2 particles, resulting in the formation of TiO2–SiO2 mixed oxides [10]. On the other hand, for TiO2/SBA-15 sample, the ratio of the intensity at 964 cm 1 to other peaks is higher than that of parent SBA-15, which is generally taken as proof of the incorporation of Ti into the framework of zeolite [17,18]. The photocatalytic experimental results are illustrated in Fig. 4 and Fig. S1. The photolysis of MO without catalyst is only 1.4 % at 50 min, which is negligible. As shown in Fig. 4a and Fig. S1a, the photocatalytic activity of TiO2/SBA-15 are increased with the increase of calcination temperature from 400–600 1C. However, the temperature beyond 600 1C results in a slight decrease in the activity because of the large particle size of TiO2. It is seen from Fig. 4b and Fig. S1b that the photocatalytic activities of TiO2/SBA15 composites are all higher than that of pure TiO2 and SBA-15. The results indicate that the titania supported on the SBA-15 framework plays a role in the decomposition of MO and provides the photocatalytic active sites. It is also seen that 17% TiO2/ SBA-15 shows the highest photocatalytic activity due to its appropriate TiO2 loading amount. When the TiO2 amount exceeds 23%, the photocatalytic activity decreases, owing to the blocking of mesopores of SBA-15 by excess titania.
964
4. Conclusion
1600
1400
1200
1000
800
600
400
Wavenumber (cm-1) Fig. 3. FT-IR spectra of SBA-15 and 17% TiO2/SBA-15 materials.
600 °C 700 °C 500 °C 400 °C
4
23% TiO /SBA15 10% TiO /SBA15
3
2
30% TiO /SBA15 TiO SBA-15
2 1
1 0
17% TiO /SBA15
4
ln (C0/C)
3 ln (C0/C)
1800
TiO2/SBA-15 photocatalysts have been successfully synthesized using inorganic metatitanic acid as titanium source by means of hydrothermal method and pyrolysis. By the use of asprepared SBA-15 materials containing template as support, most of the TiO2 particles are not loaded within the ordered channels of the support, which keep the stability of porous structural. TiO2 modified SBA-15 exhibited a significant photocatalytic activity for
0
10
20
30
Irradiation time (min)
40
50
0
0
10
20
30
Irradiation time (min)
Fig. 4. Time-course variation of ln(C0/C) of methyl orange over various photocatalysts.
40
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X.-j. Wang et al. / Materials Letters 99 (2013) 38–41
MO degradation reactions. At the optimal temperature of 600 1C, the 17% TiO2/SBA-15 exhibited the highest photocatalytic activity. Acknowledgments This work was supported by the National Natural Science Foundation of China (No. 21076060), the Program for New Century Excellent Talents in University (NCET-12-0686), the One-Hundred Outstanding Innovative Talents Scheme of Hebei Province Education Department (No. CPRC022), the Training Funds for Talents Project of Hebei Province, the Doctoral Science Foundation of Hebei University of Science and Technology (No. QD201049). the Scientific Research Foundation of Hebei Province Education Department (No. Z2012069).
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.2013. 02.060.
References [1] Li FT, Zhao Y, Liu Y, Hao YJ, Liu RH, Zhao DS. Chem Eng J 2011;173:750–9. [2] Kim SK, Chang H, Cho K, Kil DS, Cho SW, Jang HD, et al. Mater Lett 2011;65:3330–2.
41
[3] Lachheb H, Ahmed O, Houas A, Nogier JP. J Photochem Photobiol A: Chem 2011;226:1–8. [4] Huo YD, Wang XC, Wu L, Chen XF, Ding ZX, Wang XX, et al. Chemosphere 2008;72:414–21. [5] Li L, Shi JL, Yan JN, Chen HG, Zhao XG. J Mol Catal A: Chem 2004;209:227–30. [6] Wan Y, Zhao DY. Chem Rev 2007;107:2821–60. [7] Zhao DY, Feng JL, Huo QS, Melosh N, Fredrickson G, Chmelka B, et al. Science 1998;279:548–52. [8] Zhao S, Su D, Che J, Jiang BY, Orlov A. Mater Lett 2011;65:3354–7. [9] De Witte K, Busuioc AM, Meynen V, Mertens M, Bilba N, Van Tendeloo G, et al. Microporous Mesoporous Mater 2008;110:100–10. [10] Acosta-Silva YJ, Nava R, Herna´ndez-Morales V, Macı´as-Ssnchez SA, Go´mezHerrera ML, Pawelec B. Appl Catal B: Environ 2011;110:108–17. [11] Shao XC, Duan LH, Wu YY, Qin YC, Yu WG, Wang Y. Acta Phys-Chim Sin 2012;28:1467–73. [12] Zhang CS, Jiang D, Tang T, Li JH, Xu Y. Acta Phys-Chim Sin 2010;26:1330–6. [13] Zhao DY, Huo QS, Feng JL, Chmelka BF, Stucky GD. J Am Chem Soc 1998;120:6024–36. [14] Grieken RV, Aguado J, Lopez-Munoz MJ, Marugan J. J Photochem Photobiol A: Chem 2002;148:315–22. [15] Song LY, Feng D, Lee HJ, Wang CQ, Wu QY, Zhao DY, et al. J Phys Chem C 2010;114:9618–26. [16] Blasco T, Camblor MA, Corma A, Pariente JP. J Am Chem Soc 1993;115:11806–13. [17] Jung WU, Lim KT, Park SS, Lee GD, Hong SS. J Nanosci Nanotechnol 2011;11:833–7. [18] Yang J, Zhang J, Zhu LW, Chen SY, Zhang YM, Tang Y, et al. J Hazardous Mater 2006;137:952–8.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
TiO2/SBA-15 composites prepared using H2TiO3 by hydrothermal method and its photocatalytic activity Xiao-jing Wang, Fa-tang Li n, Ying-juan Hao, Shuang-jun Liu, Min-li Yang College of Science, Hebei University of Science and Technology, Shijiazhuang 050018, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 September 2012 Accepted 14 February 2013 Available online 21 February 2013
A novel approach of SBA-15 mesoporous materials decorated with various amounts of TiO2 (10–30% TiO2/SBA-15) were prepared by the post-synthesis method using metatitanic acid as precursor and template-retentive SBA-15 as support. The result shows that the silica framework was stable and it was almost not affected by appropriate titania deposition. The photocatalytic activity of the samples was tested by degradation of methyl orange (MO), which was increased with increasing TiO2 loading ratio at first and then decreased. The 17% TiO2/SBA-15 composite calcinated at 600 1C showed the highest photocatalytic ability for degradation of MO because of its appropriate amount of TiO2 and less agglomeration. & 2013 Elsevier B.V. All rights reserved.
Keywords: Nanocomposites Semiconductors Metatitanic acid TiO2 SBA-15 Photocatalysis
1. Introduction TiO2 has been considered as one of the most promising photocatalysts because of its nontoxicity, photo- and chemicalstability, low cost, and superior photocatalytic activity [1]. However, its applications are hindered by two disadvantages. Firstly, small particles tend to agglomerate into large ones, making against on catalyst performance. Secondly, TiO2 nanoparticles less than 20 nm in diameter are very active photocatalysts but such nanoparticles are somewhat impractical for industrial applications because downstream nanoparticles recycling processes are difficult [2,3]. On this basis, great efforts have been focused on developing supported titania catalysts offering high dispersed properties and easy reusing size for TiO2 [2,4]. Ordered Mesoporous Silicas (OMSs) such as SBA-15 are widely used as catalytic supports, which have high thermal and chemical stability, as well as tunable surface composition and pore size [5–7]. However, most of the reported works are mainly based on sol–gel processing using titanium alkoxides and titanium tetrachloride as the titanium sources [8–10]. The former is expensive and the latter contains chlorine, which would bring problem of environmental pollution. Therefore, it is necessary to find an inexpensive and environment-friendly reagent to prepare composite TiO2 photocatalysts. Besides, in lot of researches, the template-free supports were used. Shao et al. [11] and Zhang et al. [12] found that when template-free SBA-15 was used as a support, the dispersion
n
Corresponding author. Tel.: þ86 311 8166 9971; fax: þ 86 311 8166 8528. E-mail address: [email protected] (F.-t. Li).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.02.060
amount of anchored species was relatively low, and the particles of active species were easy to aggregate. However, less attention has been paid to the as-prepared SBA-15 materials containing template as support. In this work, a novel approach to synthesize TiO2/SBA-15 materials by using metatitanic acid as titanium source and SBA15 materials containing template as support was proposed. This strategy is not only a low cost technique, but also allows high dispersion of TiO2. It would help to improve the mesostructural stability and long-range order of the adsorbents. Its photocatalytic activity for decomposition of MO was also investigated.
2. Experiments Siliceous SBA-15 mesoporous material was synthesized according to the procedure described by Zhao et al. [13]. The Pluronic triblock copolymer P123 (BASF) was used as the structure-directing agent and tetraethylorthosilicate (TEOS) as a source of silica. In a typical synthesis, the triblock copolymer was dissolved in a mixture of deionized water and 4 M hydrochloric acid solution stirred for 1 h, after which the required amount of TEOS was added to the solution at 308 K and kept under stirring conditions for 24 h. After synthesis, the obtained solid was filtered, washed with ice distilled water and dried at room temperature in air, and the obtained white powder was asprepared SBA-15. To prepare peroxotitanate, different amounts of H2TiO3 was added into an ice-cooled solution containing H2O, H2O2 (30%) and NH4OH (28%). After being stirred for 60 min, a homogeneous pale
X.-j. Wang et al. / Materials Letters 99 (2013) 38–41
yellow-green solution was obtained and then adjusted to pH¼7 by HNO3 (2 M). Then, given amount of as-prepared SBA-15 was added in the solution. After stirring for 5 h, the samples were transferred into a Teflon reactor of 50 mL inside a stainless-steel vessel and heated at 160 1C for 6 h. After the hydrothermal treatment, the products were separated by filtration and then dried 60 1C. The samples were calcined at 400–700 1C for 2 h to obtain final TiO2/SBA-15 composites. For comparison, pure TiO2 powder was also prepared through the same procedure and calcined at 600 1C, but without SBA-15 addition. The photocatalytic experiments were carried out in a 500 mL cylindrical glass reactor inside equipped with a high-pressure mercury lamp using 300 ml MO solution with an initial concentration of 50 mg/L and 0.4 g catalyst. The concentration of MO was determined by spectroscopic analysis at 464 nm. X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) were obtained on a Bruker D8-Advance X-ray diffractometer using CuKa radiation. Transmission electron microscopy
39
(TEM) images were taken with a JEOL JEM-2010 electron microscope. Nitrogen adsorption isotherms for the SBA-15 samples were collected by Quantachrome Nova 2000 instrument. Fourier transform infrared (FT-IR) spectra were obtained using a Shimadzu IR Prestige 21 spectrometer.
3. Results and discussion Table S1 shows the textural properties of the siliceous SBA-15 and TiO2/SBA-15 samples calcinated at 600 1C. It is clear that loading TiO2 on the silica matrix slightly decreases the surface area, pore volume, and pore size of the support, which indicates that most of the TiO2 particles are not loaded within the ordered channels of the support. The structure formation process is proposed as Scheme 1. Fig. 1a shows the XRD patterns of 17% TiO2/SBA-15 materials treated at different temperature. These patterns matched well
calcine
mix peroxotitanate
P123
silica
peroxotitanat
TiO
10
20
30
40
50
2 Theta (°)
60
70
Intensity (a.u)
Intensity (a.u)
Intensity (a.u)
Scheme 1. Schematic diagram of preparation process on TiO2/SBA-15 samples.
10
20
30
40
50
60
70
2 Theta (°)
1
2
3
4
5
2 Theta (°)
Fig. 1. XRD patterns of (a) 17% TiO2/SBA-15 with different calcination temperatures, (b) x% TiO2/SBA-15 calcined at 600 1C, and (c) small-angle XRD patterns of the SBA-15 and 17% TiO2/SBA-15.
Fig. 2. TEM images of 17% TiO2/SBA-15 material.
40
X.-j. Wang et al. / Materials Letters 99 (2013) 38–41
with the standard pattern of anatase TiO2 (JCPDS 21-1272). With the increase of calcination temperature, the peaks of anatase become narrower and higher, implying the growth of TiO2 crystal. The average crystalline sizes are 8.9 nm, 9.5 nm, 12.7 nm and 14.5 nm from 400–700 1C, calculated from the most intense diffraction peak (101) corresponding to peak at 2y ¼25.31 using Scherer equation. Furthermore, the TiO2/SBA-15 calcinated at 700 1C retains the structure of anatase and no rutile peak is found, suggesting that the TiO2/SBA-15 has high thermal stability because of a stabilizing effect of silica on the anatase–rutile transition at higher temperatures [3,14] and the hindrance of interfacial energy between TiO2 and SBA-15. Wide-angle XRD patterns of the mesoporous x% TiO2/SBA-15 samples calcined at 600 1C were also recorded (shown in Fig.1b). It can be seen that the intensity of the (101) diffraction peak becomes higher with the increase of TiO2 content. Fig. 1c shows the small-angle XRD patterns of the SBA-15 and 17% TiO2/SBA-15 materials calcinated at 600 1C. The calcined SBA-15 sample displayed a well-resolved pattern with a sharp peak at about 1.01 which was consistent with the reported pattern [7]. In the case of the samples with a loading of titanium dioxide, the XRD patterns, especially the order Bragg reflections and the XRD peaks are not broadened, suggesting that the silica framework was stable and it was not affected by titania deposition. However, compared with SBA-15, the primary diffraction peak of 17% TiO2/SBA-15 shift to higher angles, which
SBA-15
Transmittance (a.u)
971
17% TiO2/SBA-15
indicates the slightly deposition of TiO2 in the mesopores [15]. These results are consistent with the BET results. Fig. 2a and b shows the TEM images of the 17% TiO2/SBA-15 sample. A well-ordered hexagonal array of mesopores can be seen when the electron beam is parallel to the main axis of the cylindrical pores. When the electron beam is perpendicular to the main axis, the presence of the parallel nanotubular pores in the parent SBA-15 matrix is evidenced. The introduction of titanium does not substantially alter the regular ordered structure of the mesopores, which is consistent with SAXS and BET results. The FT-IR spectra of the SBA-15 and 17% TiO2/SBA-15 calcinated at 600 1C are shown in Fig. 3. For parent SBA-15 silica, a weak band at about 971 cm 1 is attributed to the Si–OH stretching vibration [16]. After combining with TiO2, a small shift of about 7 cm 1 to lower frequencies is observed, showing that the incorporated TiO2 particles have been structurally combined with SiO2 particles, resulting in the formation of TiO2–SiO2 mixed oxides [10]. On the other hand, for TiO2/SBA-15 sample, the ratio of the intensity at 964 cm 1 to other peaks is higher than that of parent SBA-15, which is generally taken as proof of the incorporation of Ti into the framework of zeolite [17,18]. The photocatalytic experimental results are illustrated in Fig. 4 and Fig. S1. The photolysis of MO without catalyst is only 1.4 % at 50 min, which is negligible. As shown in Fig. 4a and Fig. S1a, the photocatalytic activity of TiO2/SBA-15 are increased with the increase of calcination temperature from 400–600 1C. However, the temperature beyond 600 1C results in a slight decrease in the activity because of the large particle size of TiO2. It is seen from Fig. 4b and Fig. S1b that the photocatalytic activities of TiO2/SBA15 composites are all higher than that of pure TiO2 and SBA-15. The results indicate that the titania supported on the SBA-15 framework plays a role in the decomposition of MO and provides the photocatalytic active sites. It is also seen that 17% TiO2/ SBA-15 shows the highest photocatalytic activity due to its appropriate TiO2 loading amount. When the TiO2 amount exceeds 23%, the photocatalytic activity decreases, owing to the blocking of mesopores of SBA-15 by excess titania.
964
4. Conclusion
1600
1400
1200
1000
800
600
400
Wavenumber (cm-1) Fig. 3. FT-IR spectra of SBA-15 and 17% TiO2/SBA-15 materials.
600 °C 700 °C 500 °C 400 °C
4
23% TiO /SBA15 10% TiO /SBA15
3
2
30% TiO /SBA15 TiO SBA-15
2 1
1 0
17% TiO /SBA15
4
ln (C0/C)
3 ln (C0/C)
1800
TiO2/SBA-15 photocatalysts have been successfully synthesized using inorganic metatitanic acid as titanium source by means of hydrothermal method and pyrolysis. By the use of asprepared SBA-15 materials containing template as support, most of the TiO2 particles are not loaded within the ordered channels of the support, which keep the stability of porous structural. TiO2 modified SBA-15 exhibited a significant photocatalytic activity for
0
10
20
30
Irradiation time (min)
40
50
0
0
10
20
30
Irradiation time (min)
Fig. 4. Time-course variation of ln(C0/C) of methyl orange over various photocatalysts.
40
50
X.-j. Wang et al. / Materials Letters 99 (2013) 38–41
MO degradation reactions. At the optimal temperature of 600 1C, the 17% TiO2/SBA-15 exhibited the highest photocatalytic activity. Acknowledgments This work was supported by the National Natural Science Foundation of China (No. 21076060), the Program for New Century Excellent Talents in University (NCET-12-0686), the One-Hundred Outstanding Innovative Talents Scheme of Hebei Province Education Department (No. CPRC022), the Training Funds for Talents Project of Hebei Province, the Doctoral Science Foundation of Hebei University of Science and Technology (No. QD201049). the Scientific Research Foundation of Hebei Province Education Department (No. Z2012069).
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.2013. 02.060.
References [1] Li FT, Zhao Y, Liu Y, Hao YJ, Liu RH, Zhao DS. Chem Eng J 2011;173:750–9. [2] Kim SK, Chang H, Cho K, Kil DS, Cho SW, Jang HD, et al. Mater Lett 2011;65:3330–2.
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