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Porous SrTiO3 spheres with enhanced photocatalytic performance
Materials Letters 67 (2012) 131–134
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Porous SrTiO3 spheres with enhanced photocatalytic performance Wenjun Dong a, b,⁎, Xiaoyun Li b, Jie Yu a, Wanchun Guo a, Bingjie Li b, Li Tan a, Chaorong Li b, Jianjun Shi b, Ge Wang a,⁎⁎ a b
School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, People's Republic of China Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Hangzhou 310018, People's Republic of China
a r t i c l e
i n f o
Article history: Received 17 August 2011 Accepted 9 September 2011 Available online 16 September 2011 Keywords: Ceramics Structural SrTiO3 Porous Photocatalytic
a b s t r a c t Porous SrTiO3 spheres were successfully synthesized by a convenient hydrothermal method, employing SrCl2 as Sr source and titanate nanotube as Ti precursor. In this reaction, when short titanate nanotube was used as Ti precursor, porous SrTiO3 spheres were generated for the aggregation of the nanotube@SrTiO3 heteronanostructure. Whereas long titanate nanowire was used as the Ti precursor, solid SrTiO3 spheres were obtained due to the SrTiO3 which grows up gradually on the titanate nanowire. The morphology and the pore size of the SrTiO3 sphere structures can be easily controlled by simply adjusting the reaction time, reaction temperature and the Ti precursor. The porous SrTiO3 spheres exhibited enhanced photocatalytic activity which could achieve 100% degradation of Rhodamine B with a UV irradiation for 20 min. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Strontium titanate (SrTiO3), as an important n-type semiconductor with band gap of about 3.2 eV, is one of the most important multifunctional perovskite materials possessing a suite of useful properties, such as high dielectric constant, incipient ferroelectric property, photocatalyst and photoelectrodes for splitting water [1–2]. Especially, the porous SrTiO3 nanostructure, combined the shape-specific and the porous natures, lead to collective functions to improve the photocatalytic activity [3,4]. In 2004, Grosso et al. synthesized of porous SrTiO3 film by an evaporation-induced self-assembly method [5]. Later, the assembled porous SrTiO3 nanocrystals have been synthesized successfully via a sol–gel method with the aid of a structure-directing agent [6]. Recently, Xiao W. et al. reported the preparation of mesoporous SrTiO3 spheres with an aggregation motif through a polyvinyl alcohol-assisted hydrothermal route [4]. However, the synthesis of porous SrTiO3 crystalline without using organic agents still remains as a challenge. Usually, mesoporous materials were synthesized inevitably under the help of surfactant as soft template or mesoporous oxides (usually silica) as hard template [7]. Recently, sol–gel method and anodization method also have been used to synthesize porous materials without using the template. However, those methods are complicated and limited to selected materials types [7]. In this paper, we reported, for the first time, the synthesis of porous SrTiO3 nanostructure using a free-template
⁎ Corresponding to: Ge Wang, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, People's Republic of China. ⁎⁎ Corresponding authors. Tel.: + 86 10 62333765; fax: + 86 10 62327878. E-mail addresses: [email protected] (W. Dong), [email protected] (G. Wang). 0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.09.045
hydrothermal method. The diameter of the SrTiO3 sphere could be tuned from 100 nm to 300 nm, and the pore size could be controlled by varying reaction time and temperature. The porous SrTiO3 exhibits much enhanced photocatalytic activity for the degradation of Rhodamine B under UV light irradiation, which may be attributed to the high surface area of the nanostructured SrTiO3 and high ratio exposed photocatalytically active facet of SrTiO3 crystalline. 2. Experimental details 2.1. Preparation of SrTiO3 nanostructures In a typical titanate nanotube synthesis, 0.20 g of P25 was introduced into 40 mL of NaOH solution (10 mol/L) in a 150 mL Teflonlined autoclave for 3 days at 150 °C, a white pulp-like product of the long nanotube was collected, and then washed with distilled water [8]. For the synthesis of porous SrTiO3 nanostructure, 10 mL of SrCl2 saturated solution, an amount of NaOH and titanate nanotube were placed in the Teflon-lined vessel. Subsequently, the vessel was sealed and heated, and then the products were collected and washed with deionized water, and dried in air. 2.2. Characterization The morphology of the as-obtained samples was characterized on a Hitachi 4800 scanning electron microscopy (SEM). Transmission electron microscopy (HRTEM) studies were carried out on a JEOL JEM 2010 transmission electron microscopy. The phase composition was determined by X-ray diffraction (XRD) experiments on a X′ TRA with CuKα radiation (λ = 1.5418 Å).
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2.3. Measurements of photocatalytic activities
(110)
* SrCO3
The photocatalytic activity of the porous SrTiO3 spheres was evaluated by the degradation of Rhodamine B (RhB). 30 mg of porous SrTiO3 spheres was dispersed in 30 mL of 2 × 10 − 5 mol/L of RhB solution. The UV illumination (λ = 254 nm) from the lamp was about 5 mm above the solution, and the RhB absorbency was measured using a UV–visible spectrometer.
(200)
(211)
(111) (220) (100) *
*
*
*
*
* *
(210)
12h
(310) (300)
3h
3. Results and discussion 3.1. Effect of reaction time on the microstructure
1h
The evolution of the porous SrTiO3 nanostructure at 200 °C in 1.0 mol/L NaOH solution with different reaction time was studied, and the morphologies of the as-prepared samples were shown in Fig. 1. Fig. 1a depicted the SEM image of the as-obtained products after 1 h of treatment, and the as-prepared globular particles were ~ 150 nm in diameter. SEM image showed that the globular particles were composed by small nanoparticles (Fig. 1a). As the reaction time proceeded to 3 h, well-defined nanocrystals of 200 nm in diameter were synthesized. Interestingly, pores with several tens nanometer in diameter were presented on the globular nanoparticles, which properly induced by the etching (Fig. 1b). After 12 h of hydrothermal treatment, porous SrTiO3 nanostructures with 100–300 nm in diameter were obtained. The pore was 10–50 nm in diameter, and several tens nm in depth (Fig. 1c). The diameter of the globular particles and the pore size were grown larger along the extending reaction time. When the reaction time was extended to 24 h, the uniform spheres with ~ 200 nm in diameter were prepared, and the pore size of the spheres was increased to 50–100 nm in diameter, and several tens in depth. Further reaction even could induce the porous hollow SrTiO3 sphere (Fig. 1d).
20
30
40
50
60
70
80
Fig. 2. XRD patterns of as-obtained SrTiO3 products.
Fig. 2 showed the XRD patterns of the synthesized samples at 200 °C in 1.0 mol/L NaOH solution. All the diffraction peaks of SrTiO3 in Fig. 2 could be indexed to standard SrTiO3 cubic structure (JPCDSNo.35-0734). Due to the coexistence of SrTiO3 and SrCO3 in the air-operating conditions by hydrothermal method, so SrCO3 peak also could be observed in the XRD patterns. Interestedly, the SrCO3 particles in the SrTiO3 sphere could be removed by dilute acid, which could further improve the porous structure. 3.2. Effect of reaction temperature on the structure On this basis, the temperature effect on the SrTiO3 morphology was likewise studied in 1.0 mol/L NaOH solution for 24 h. At 160 °C, the porous SrTiO3 sphere with 200–300 nm in diameter could be
a
b
c
d
Fig. 1. SEM images of as-obtained SrTiO3 products in different reaction times, (a) 1 h; (b) 3 h; (c) 12 h; (d) 24 h.
W. Dong et al. / Materials Letters 67 (2012) 131–134
133
a SrCl2 <150 oC nanotube
P25+NaOH
Porous SrTiO3
Na2Ti3O7 >150 oC
SrCl2 nanowire
Solid SrTiO3
b
c
Fig. 3. (a) Schematic illustration of the formation mechanism of SrTiO3, (b) as-prepared porous SrTiO3 products from titanate nanotube precursor, and (c) as-prepared solid SrTiO3 products from titanate nanowire precursor.
3.3. Formation mechanism Recently, researchers have focused on the perovskite nanostructure fabrication from protonated titania nanostructure because titanate is more active than crystallized TiO2 [9]. Ti precursor effect such as titanate nanotube and nanowire on the morphology of SrTiO3 microstructure was likewise studied at 200 °C in 1.0 mol/L NaOH solution for 24 h. Based on the morphological evolution of the time-dependent experiment result, the growth mechanisms of SrTiO3 nanostructures were explored (as shown in Fig. 3a). When the precursor was titanate nanotube, crystallites were produced by a quick nucleation, these formed crystallites were effectively consumed during the aggregation process, and aggregations of the nanotube@SrTiO3 heteronanostructure were appeared. As a result, porous SrTiO3 particles could be obtained through a subsequent ripening process (Fig. 3b) [10]. On the other hand, when long titanate nanowire precursor was used, the dissolved Ti source could supply slowly for the nucleation and growth of SrTiO3, so the SrTiO3 aggregation would increases gradually to solid sphere (Fig. 3c). It indicated that the highly active titanate nanotube precursor could improve the uniformity of the products through the effective separation of nucleation and growth stage [10]. This strategy was similar to a selflimiting-aggregation growth model described by Lee et al. [11]. 3.4. Photocatalytic activities Generally, the porous materials, the large pore size and high pore volume have remarkable advantages in bulky molecular adsorption because pore size could facilitate the diffusion of dye molecules inside
the pores, and high pore volume paves the way for more accessible adsorption sites [12]. The specific surface area of as-prepared the porous and solid SrTiO3 sphere is 25.8 and 12.1 m 2/g. UV–visible absorbance spectra of as-obtained porous SrTiO3 spheres photodegrading the RhB solution were presented in Fig. 4. A blank test using the RhB solution with a UV illumination for 20 min showed that the RhB concentration was decreased by 40%. The porous catalyst showed better adsorption property than that of solid nanosphere, and 18% and 3.6% of RhB were decreased respectively in 20 min. The porous SrTiO3 sphere photocatalyst could decompose 78.8% of RhB with a UV irradiation for 10 min, and almost 100% of RhB was degraded for 20 min. However, the solid SrTiO3 nanoparticle could reduce only 69.2% of RhB with a UV irradiation for 10 min. During the photodegradation process, the absorption peak shifted from 554 nm to 539 nm gradually, which was similar to the hypsochromic shifts in the RhB/TiO2 and RhB/Bi2WO6 systems [13]. This was because, under UV irradiation,
1.2 0min
1.0
5min 10min
0.8
15min 20min
Abs.
obtained, and the surface of the sphere was smooth. When the reaction temperature was increased to 200 °C, the sphere with rough surface could be prepared. SEM image confirmed that the pore on the surface of nanoparticle became deeper and bigger than as-obtained in lower temperature. The SrTiO3 spheres were cracked when the temperature reached 240 °C, which may attribute to the splitting of the porous structure at high temperature.
25min
0.6
0.4
0.2
0.0 400
450
500
550
600
650
700
Wavelength (nm) Fig. 4. Decomposition of Rhodamine B with porous SrTiO3 sphere photocatalyst.
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the dye was de-ethylated in a stepwise manner with the color of the solution changing from an initial red to a light yellow [3].
tion Bureau Foundation (2011B19) and National Natural Science Foundation of China (50972130, 20701033, 50836001, 10874153).
4. Conclusions
References
In conclusion, porous and solid SrTiO3 spheres were successfully prepared by a template-free hydrothermal method by using titanate nanotube and nanowire precursor, respectively. The effects of reaction time, reaction temperature and precursor on the morphology and phase composition were studied, and the pore size of the assynthesized porous SrTiO3 spheres could be tuned by varying reaction time and temperature. The porous SrTiO3 spheres were able to degrade 100% RhB with a UV irradiation for 20 min. In addition, it is expected that the synthesis method may be extended to other porous perovskite structures. Acknowledgment This work was supported by China Postdoctoral Science Foundation (201003048, 20090450292), the Fundamental Research Funds for the Central Universities (FRF-TP-09-009B), Zhejiang Environmental Protec-
[1] Tagantsev AK, Sherman VO, Astafiev KF, Venkatesh J, Setter N. J Electroceram 2003;11:5–66. [2] Modeshia DR, Walton RI. Chem Soc Rev 2010;39:4303–25. [3] Wang JS, Yin S, Komatsu M, Zhang QW, Saito F, Sato T. J Photochem Photobiol A 2004;165:149–56. [4] Wei X, Xu G, Ren ZH, Xu CX, Weng WJ, Shen G, et al. J Am Ceram Soc 2010;93: 1297–305. [5] Grosso D, Boissiere C, Smarsly B, Brezesinski T, Pinna N, Albouy PA, et al. Nat Mater 2004;3:787–92. [6] Puangpetch T, Sreethawong T, Yoshikawa S, Chavadej S. J Mol Catal A 2008;287: 70–9. [7] Yu C, Zhang L, Shi J, Zhao J, Gao J, Yan D. Adv Funct Mater 2008;18:1544–54. [8] Suetake J, Nosaka AY, Hodouchi K, Matsubara H, Nosaka Y. J Phys Chem C 2008;112:18474–82. [9] Li Y, Gao XP, Li GR, Pan GL, Yan TY, Zhu HY. J Phys Chem C 2009;113:4386–94. [10] Tian XL, Li J, Chen K, Han J, Pan SL, Wang YJ, et al. Cryst Growth Des 2010;10: 3990–5. [11] Lee SH, Her YS, Matijevic E. J Colloid Interface Sci 1997;186:193–202. [12] Morales W, Cason M, Aina O, de Tacconi NR, Rajeshwar K. J Am Chem Soc 2008;130:6318–9. [13] Zhang C, Zhu YF. Chem Mater 2005;17:3537–45.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Porous SrTiO3 spheres with enhanced photocatalytic performance Wenjun Dong a, b,⁎, Xiaoyun Li b, Jie Yu a, Wanchun Guo a, Bingjie Li b, Li Tan a, Chaorong Li b, Jianjun Shi b, Ge Wang a,⁎⁎ a b
School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, People's Republic of China Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Hangzhou 310018, People's Republic of China
a r t i c l e
i n f o
Article history: Received 17 August 2011 Accepted 9 September 2011 Available online 16 September 2011 Keywords: Ceramics Structural SrTiO3 Porous Photocatalytic
a b s t r a c t Porous SrTiO3 spheres were successfully synthesized by a convenient hydrothermal method, employing SrCl2 as Sr source and titanate nanotube as Ti precursor. In this reaction, when short titanate nanotube was used as Ti precursor, porous SrTiO3 spheres were generated for the aggregation of the nanotube@SrTiO3 heteronanostructure. Whereas long titanate nanowire was used as the Ti precursor, solid SrTiO3 spheres were obtained due to the SrTiO3 which grows up gradually on the titanate nanowire. The morphology and the pore size of the SrTiO3 sphere structures can be easily controlled by simply adjusting the reaction time, reaction temperature and the Ti precursor. The porous SrTiO3 spheres exhibited enhanced photocatalytic activity which could achieve 100% degradation of Rhodamine B with a UV irradiation for 20 min. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Strontium titanate (SrTiO3), as an important n-type semiconductor with band gap of about 3.2 eV, is one of the most important multifunctional perovskite materials possessing a suite of useful properties, such as high dielectric constant, incipient ferroelectric property, photocatalyst and photoelectrodes for splitting water [1–2]. Especially, the porous SrTiO3 nanostructure, combined the shape-specific and the porous natures, lead to collective functions to improve the photocatalytic activity [3,4]. In 2004, Grosso et al. synthesized of porous SrTiO3 film by an evaporation-induced self-assembly method [5]. Later, the assembled porous SrTiO3 nanocrystals have been synthesized successfully via a sol–gel method with the aid of a structure-directing agent [6]. Recently, Xiao W. et al. reported the preparation of mesoporous SrTiO3 spheres with an aggregation motif through a polyvinyl alcohol-assisted hydrothermal route [4]. However, the synthesis of porous SrTiO3 crystalline without using organic agents still remains as a challenge. Usually, mesoporous materials were synthesized inevitably under the help of surfactant as soft template or mesoporous oxides (usually silica) as hard template [7]. Recently, sol–gel method and anodization method also have been used to synthesize porous materials without using the template. However, those methods are complicated and limited to selected materials types [7]. In this paper, we reported, for the first time, the synthesis of porous SrTiO3 nanostructure using a free-template
⁎ Corresponding to: Ge Wang, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, People's Republic of China. ⁎⁎ Corresponding authors. Tel.: + 86 10 62333765; fax: + 86 10 62327878. E-mail addresses: [email protected] (W. Dong), [email protected] (G. Wang). 0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.09.045
hydrothermal method. The diameter of the SrTiO3 sphere could be tuned from 100 nm to 300 nm, and the pore size could be controlled by varying reaction time and temperature. The porous SrTiO3 exhibits much enhanced photocatalytic activity for the degradation of Rhodamine B under UV light irradiation, which may be attributed to the high surface area of the nanostructured SrTiO3 and high ratio exposed photocatalytically active facet of SrTiO3 crystalline. 2. Experimental details 2.1. Preparation of SrTiO3 nanostructures In a typical titanate nanotube synthesis, 0.20 g of P25 was introduced into 40 mL of NaOH solution (10 mol/L) in a 150 mL Teflonlined autoclave for 3 days at 150 °C, a white pulp-like product of the long nanotube was collected, and then washed with distilled water [8]. For the synthesis of porous SrTiO3 nanostructure, 10 mL of SrCl2 saturated solution, an amount of NaOH and titanate nanotube were placed in the Teflon-lined vessel. Subsequently, the vessel was sealed and heated, and then the products were collected and washed with deionized water, and dried in air. 2.2. Characterization The morphology of the as-obtained samples was characterized on a Hitachi 4800 scanning electron microscopy (SEM). Transmission electron microscopy (HRTEM) studies were carried out on a JEOL JEM 2010 transmission electron microscopy. The phase composition was determined by X-ray diffraction (XRD) experiments on a X′ TRA with CuKα radiation (λ = 1.5418 Å).
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W. Dong et al. / Materials Letters 67 (2012) 131–134
2.3. Measurements of photocatalytic activities
(110)
* SrCO3
The photocatalytic activity of the porous SrTiO3 spheres was evaluated by the degradation of Rhodamine B (RhB). 30 mg of porous SrTiO3 spheres was dispersed in 30 mL of 2 × 10 − 5 mol/L of RhB solution. The UV illumination (λ = 254 nm) from the lamp was about 5 mm above the solution, and the RhB absorbency was measured using a UV–visible spectrometer.
(200)
(211)
(111) (220) (100) *
*
*
*
*
* *
(210)
12h
(310) (300)
3h
3. Results and discussion 3.1. Effect of reaction time on the microstructure
1h
The evolution of the porous SrTiO3 nanostructure at 200 °C in 1.0 mol/L NaOH solution with different reaction time was studied, and the morphologies of the as-prepared samples were shown in Fig. 1. Fig. 1a depicted the SEM image of the as-obtained products after 1 h of treatment, and the as-prepared globular particles were ~ 150 nm in diameter. SEM image showed that the globular particles were composed by small nanoparticles (Fig. 1a). As the reaction time proceeded to 3 h, well-defined nanocrystals of 200 nm in diameter were synthesized. Interestingly, pores with several tens nanometer in diameter were presented on the globular nanoparticles, which properly induced by the etching (Fig. 1b). After 12 h of hydrothermal treatment, porous SrTiO3 nanostructures with 100–300 nm in diameter were obtained. The pore was 10–50 nm in diameter, and several tens nm in depth (Fig. 1c). The diameter of the globular particles and the pore size were grown larger along the extending reaction time. When the reaction time was extended to 24 h, the uniform spheres with ~ 200 nm in diameter were prepared, and the pore size of the spheres was increased to 50–100 nm in diameter, and several tens in depth. Further reaction even could induce the porous hollow SrTiO3 sphere (Fig. 1d).
20
30
40
50
60
70
80
Fig. 2. XRD patterns of as-obtained SrTiO3 products.
Fig. 2 showed the XRD patterns of the synthesized samples at 200 °C in 1.0 mol/L NaOH solution. All the diffraction peaks of SrTiO3 in Fig. 2 could be indexed to standard SrTiO3 cubic structure (JPCDSNo.35-0734). Due to the coexistence of SrTiO3 and SrCO3 in the air-operating conditions by hydrothermal method, so SrCO3 peak also could be observed in the XRD patterns. Interestedly, the SrCO3 particles in the SrTiO3 sphere could be removed by dilute acid, which could further improve the porous structure. 3.2. Effect of reaction temperature on the structure On this basis, the temperature effect on the SrTiO3 morphology was likewise studied in 1.0 mol/L NaOH solution for 24 h. At 160 °C, the porous SrTiO3 sphere with 200–300 nm in diameter could be
a
b
c
d
Fig. 1. SEM images of as-obtained SrTiO3 products in different reaction times, (a) 1 h; (b) 3 h; (c) 12 h; (d) 24 h.
W. Dong et al. / Materials Letters 67 (2012) 131–134
133
a SrCl2 <150 oC nanotube
P25+NaOH
Porous SrTiO3
Na2Ti3O7 >150 oC
SrCl2 nanowire
Solid SrTiO3
b
c
Fig. 3. (a) Schematic illustration of the formation mechanism of SrTiO3, (b) as-prepared porous SrTiO3 products from titanate nanotube precursor, and (c) as-prepared solid SrTiO3 products from titanate nanowire precursor.
3.3. Formation mechanism Recently, researchers have focused on the perovskite nanostructure fabrication from protonated titania nanostructure because titanate is more active than crystallized TiO2 [9]. Ti precursor effect such as titanate nanotube and nanowire on the morphology of SrTiO3 microstructure was likewise studied at 200 °C in 1.0 mol/L NaOH solution for 24 h. Based on the morphological evolution of the time-dependent experiment result, the growth mechanisms of SrTiO3 nanostructures were explored (as shown in Fig. 3a). When the precursor was titanate nanotube, crystallites were produced by a quick nucleation, these formed crystallites were effectively consumed during the aggregation process, and aggregations of the nanotube@SrTiO3 heteronanostructure were appeared. As a result, porous SrTiO3 particles could be obtained through a subsequent ripening process (Fig. 3b) [10]. On the other hand, when long titanate nanowire precursor was used, the dissolved Ti source could supply slowly for the nucleation and growth of SrTiO3, so the SrTiO3 aggregation would increases gradually to solid sphere (Fig. 3c). It indicated that the highly active titanate nanotube precursor could improve the uniformity of the products through the effective separation of nucleation and growth stage [10]. This strategy was similar to a selflimiting-aggregation growth model described by Lee et al. [11]. 3.4. Photocatalytic activities Generally, the porous materials, the large pore size and high pore volume have remarkable advantages in bulky molecular adsorption because pore size could facilitate the diffusion of dye molecules inside
the pores, and high pore volume paves the way for more accessible adsorption sites [12]. The specific surface area of as-prepared the porous and solid SrTiO3 sphere is 25.8 and 12.1 m 2/g. UV–visible absorbance spectra of as-obtained porous SrTiO3 spheres photodegrading the RhB solution were presented in Fig. 4. A blank test using the RhB solution with a UV illumination for 20 min showed that the RhB concentration was decreased by 40%. The porous catalyst showed better adsorption property than that of solid nanosphere, and 18% and 3.6% of RhB were decreased respectively in 20 min. The porous SrTiO3 sphere photocatalyst could decompose 78.8% of RhB with a UV irradiation for 10 min, and almost 100% of RhB was degraded for 20 min. However, the solid SrTiO3 nanoparticle could reduce only 69.2% of RhB with a UV irradiation for 10 min. During the photodegradation process, the absorption peak shifted from 554 nm to 539 nm gradually, which was similar to the hypsochromic shifts in the RhB/TiO2 and RhB/Bi2WO6 systems [13]. This was because, under UV irradiation,
1.2 0min
1.0
5min 10min
0.8
15min 20min
Abs.
obtained, and the surface of the sphere was smooth. When the reaction temperature was increased to 200 °C, the sphere with rough surface could be prepared. SEM image confirmed that the pore on the surface of nanoparticle became deeper and bigger than as-obtained in lower temperature. The SrTiO3 spheres were cracked when the temperature reached 240 °C, which may attribute to the splitting of the porous structure at high temperature.
25min
0.6
0.4
0.2
0.0 400
450
500
550
600
650
700
Wavelength (nm) Fig. 4. Decomposition of Rhodamine B with porous SrTiO3 sphere photocatalyst.
134
W. Dong et al. / Materials Letters 67 (2012) 131–134
the dye was de-ethylated in a stepwise manner with the color of the solution changing from an initial red to a light yellow [3].
tion Bureau Foundation (2011B19) and National Natural Science Foundation of China (50972130, 20701033, 50836001, 10874153).
4. Conclusions
References
In conclusion, porous and solid SrTiO3 spheres were successfully prepared by a template-free hydrothermal method by using titanate nanotube and nanowire precursor, respectively. The effects of reaction time, reaction temperature and precursor on the morphology and phase composition were studied, and the pore size of the assynthesized porous SrTiO3 spheres could be tuned by varying reaction time and temperature. The porous SrTiO3 spheres were able to degrade 100% RhB with a UV irradiation for 20 min. In addition, it is expected that the synthesis method may be extended to other porous perovskite structures. Acknowledgment This work was supported by China Postdoctoral Science Foundation (201003048, 20090450292), the Fundamental Research Funds for the Central Universities (FRF-TP-09-009B), Zhejiang Environmental Protec-
[1] Tagantsev AK, Sherman VO, Astafiev KF, Venkatesh J, Setter N. J Electroceram 2003;11:5–66. [2] Modeshia DR, Walton RI. Chem Soc Rev 2010;39:4303–25. [3] Wang JS, Yin S, Komatsu M, Zhang QW, Saito F, Sato T. J Photochem Photobiol A 2004;165:149–56. [4] Wei X, Xu G, Ren ZH, Xu CX, Weng WJ, Shen G, et al. J Am Ceram Soc 2010;93: 1297–305. [5] Grosso D, Boissiere C, Smarsly B, Brezesinski T, Pinna N, Albouy PA, et al. Nat Mater 2004;3:787–92. [6] Puangpetch T, Sreethawong T, Yoshikawa S, Chavadej S. J Mol Catal A 2008;287: 70–9. [7] Yu C, Zhang L, Shi J, Zhao J, Gao J, Yan D. Adv Funct Mater 2008;18:1544–54. [8] Suetake J, Nosaka AY, Hodouchi K, Matsubara H, Nosaka Y. J Phys Chem C 2008;112:18474–82. [9] Li Y, Gao XP, Li GR, Pan GL, Yan TY, Zhu HY. J Phys Chem C 2009;113:4386–94. [10] Tian XL, Li J, Chen K, Han J, Pan SL, Wang YJ, et al. Cryst Growth Des 2010;10: 3990–5. [11] Lee SH, Her YS, Matijevic E. J Colloid Interface Sci 1997;186:193–202. [12] Morales W, Cason M, Aina O, de Tacconi NR, Rajeshwar K. J Am Chem Soc 2008;130:6318–9. [13] Zhang C, Zhu YF. Chem Mater 2005;17:3537–45.