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Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis
Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Q1 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis Wei Zhao n, Hongxing Wang, Xiangning Feng, Yubo Zhang, Shimeng Zhang School of Material Science and Engineering, Tianjin Chengjian University, Jinjing Road 26, Xiqing district, Tianjin 300384, China
art ic l e i nf o
a b s t r a c t
Article history: Received 1 April 2015 Received in revised form 10 May 2015 Accepted 18 May 2015
Hierarchically structured spherical TiO2 particles were synthesized in a two-step process. Firstly, amorphous spherical TiO2 precursor particles with narrow size distribution and good dispersibility were obtained by hydrolysis from Ti(SO4)2 using polyvinylpyrrolidone (PVP) as surfactants. The surface microstructures of the TiO2 precursors were modified in different solvothermal conditions. The results showed that lychee-like TiO2 crystals were formed using dimethylformamide (DMF) and Ethylene glycol (EG) solvents by solvothermal treatment at 180 °C for 2 h. When choosing cetyltrimethylammonium bromide (CTAB) as the surfactant, TiO2 crystals with an orange peel-like surface were obtained. The hierarchically spherical TiO2 showed good photodegradation rate in methylene blue (MB) solution under UV irradiation. These amorphous spherical TiO2 particles are also the precursors to form the similarly shaped perovskite titanate through A-site ion-exchange reactions. & 2015 Elsevier B.V. All rights reserved.
Keywords: Solvothermal Structural Hierarchical TiO2 Photodegradation
1. Introduction The hierarchical nanostructures built from nanounits, such as nanoparticles, nanorods, nanowires and nanosheets exhibit unique physical and chemical properties. These materials, which are different from its building blocks, have been widely investigated [1,2]. TiO2 has been widely used in the fields of energy and environmental engineering since the discovery of the phenomenon of photocatalytic splitting of water on a TiO2 electrode in 1972 [3]. To make the best use of solar energy, hierarchical structured TiO2 with high stability, monodispersible nature, good crystallinity, and a large specific surface area is required to improve photocatalytic performance. Constructed assemblies of TiO2 micrometer-sized microspheres will allow the photocatalyst to be easily recovered from the working suspension after use, while the nanometer-sized building units provide a greater available surface area for dye loading. Sun [4] proposed a novel concept of TiO2 hierarchical spheres for high efficiency dye-sensitised solar cells, which showed superior light-scattering capacity and faster charge transport for efficient charge collection. Researchers have carried out studies on different hierarchical TiO2 structures [5–8]. Despite the reasonable power conversion efficiency achieved with these TiO2 hierarchical microspheres, most synthesis processes on that have poor control over the morphology and density of the branches, affecting the n
Corresponding author. Fax: þ 86 2223085110. E-mail address: [email protected] (W. Zhao).
photonic properties. Herein, we report a solvothermal method that provides a facile way to control the hierarchical structured TiO2 in a predictable manner. The obtained products show large specific surface area and good photocatalytic activities.
2. Experimental details Amorphous spherical TiO2 particles were prepared by controlling the hydrolysis of Ti (SO4)2 in a manner that has been previously reported [9]. Typically, the solution of Ti (SO4)2 (4 mmol) in 75 mL de-ionized water was mixed with PVP (2.0 g), 1-propanol (75 mL). The mixture was stirred for 3 h at 70 °C and then washed and aged in the 1 mol/L alkaline solution. 0.4 g dried amorphous TiO2 particles were redispersed in 10 mL de-ionized water and mixed with one of three solutions (10 mL DMF, 0.1 g CTAB in 10 mL de-ionized water, or 10 mL EG). The mixture was transferred into a 25 mL Teflon-lined stainless steel autoclave, sealed and heated to 180 °C for 2 h. After the reaction, the product was washed with de-ionized water and ethanol to remove any residue, and then dried in an oven at 60 °C for 4 h. For further research, the metal salt Sr (NO3)2 was added into the EG and water solvents to provide A-site ions for the ion-exchange reaction to form perovskite titanate (SrTiO3), the atomic ratio of Sr to Ti is 2:1. Structural and Morphological investigations of the samples were recorded on a Rigaku 2500 powder X-ray diffractometer with Cu Kα (λ ¼0.15406 nm) and a field-emission scanning electron
http://dx.doi.org/10.1016/j.matlet.2015.05.131 0167-577X/& 2015 Elsevier B.V. All rights reserved.
Please cite this article as: Zhao W, et al. Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis. Mater Lett (2015), http://dx.doi.org/10.1016/j.matlet.2015.05.131i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
W. Zhao et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
2
microscope (FE-SEM LEO-1530). The BET test was carried on the surface area and pore-size analyzer (Quantachrome Nova stationA 3200). The photocatalytic activity of the synthesized powders were investigated using Vis spectrophotometer (7230G, Shanghai) by the photodegradation of MB (20 mg/L), under UV irradiation (λ ¼365 nm) using a method we reported in a previous study [10].
3. Results and discussion Fig. 1 shows the morphologies of TiO2 with different surface modifications. Each top right inset is an enlarged detail of the corresponding image. All images show similar good disperse microspheres. The amorphous TiO2 precursor particles with an average diameter of 700 nm in Fig. 1a exhibit a smoother surface compared with other samples. Fig. 1b is the TiO2 hydrothermally treated in the mixed solution of de-ionized water and DMF (the volume ratio is 1:1), which showed lychee-like microcrystals with a spherical shape, and the microspheres are composed of nanoparticles distributed uniformly over the surface. The microspheres in Fig.1c also illustrated the lychee-like morphology in EG solvothermal reaction. The hierarchical nanostructures, however, was not as homogenous as the DMF one. When choosing CTAB as the surfactant in the hydrothermal treatment, TiO2 crystals with orange peel-like surfaces are obtained (Fig. 1d). Fig. 2 shows the photocatalytic activities of TiO2, with the modifications using DMF, CTAB, and EG, after the dark absorption for the hierarchical TiO2, the degree of MB degradation under 60 min of UV light irradiation is about 100%, 100%, and 93%, respectively. The lychee-like TiO2 microspheres in the DMF solvothermal treatment show the highest activity, as they could photodegrade the MB in 45 min under UV light. The color of MB solution fades away in the presence of the TiO2 with orange peel-like surface (CTAB sample)
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Time (min) Fig. 2. The photodegradation of MB in the presence of different preparations of TiO2.
and another lychee-like surface (EG sample) in 1 h. The amorphous TiO2 absorbs MB during the dark reaction and then behaves similar with the blank sample, which indicates the amorpous TiO2 particles have little photocatylic activities. These findings show that hierarchically structured TiO2 products with high specific surface area not only retain the benefits of the crystalline TiO2 for photocatalytic processes; additionally, the introduction of microstructures appearing on the surface of microparticles can enhance the optical absorption and active sites. N2 adsorption–desorption isotherms and pore-size distribution curves of TiO2 are shown in Fig. 3. According to the International
Fig. 1. SEM images of TiO2 with different modifications (a) amorphous particles (b) DMF (c) EG and (d) CTAB.
Please cite this article as: Zhao W, et al. Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis. Mater Lett (2015), http://dx.doi.org/10.1016/j.matlet.2015.05.131i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
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Fig. 3. N2 adsorption–desorption isotherms and corresponding pore size distribution curves of TiO2 samples with different modifications by (a) EG, (b) DMF, and (c) CTAB.
Union of Pure and Applied Chemistry (IUPAC) classification, all the isotherms belong to type IV, indicating that the samples possess porous structures [11]. For the representative sample a (Fig. 3a), the adsorption amount increases monotonously at a high P/P0 (P/ P0 40.9) without an adsorption limitation, suggesting that large pores formed primarily as a result of the aggregation of large particles. In samples b and c, an N2 adsorption–desorption hysteresis loop occurs in the P/P0 ¼0.4-0.8 range, which is indicative of a typical mesoporous material [12]. From the N2 desorption branch, the Barrett–Joyner–Halenda (BJH) average pore width of sample b was about 3.1 nm, the narrow distribution centered on 5 nm. No peaks exist in the curves of sample a and sample c in Fig.3b, suggesting the existence of macropores. The calculated Brunauer–Emmett–Teller (BET) surface areas are 5.84, 39.3, 106.7, and 109.4 m2/g for the amorphous TiO2 and TiO2 modified with EG, DMF, and CTAB, respectively. The results show that the DMF one with large BET surface and homogeneous morphology showed good photodegradation on the MB, which confirms the results of the photocatalytic activities. The XRD pattern of TiO2 modified with DMF is shown in Fig. 4a, the positions of diffraction peaks matched the anatase TiO2 (JCPDS no. 21-1272). After further treatment with the Sr resources, SrTiO3 was obtained (No. 35-0734, in Fig.4a). As shown in Fig. 4b, hierarchical flower-like SrTiO3 with 3D frameworks directly grows on the microspheres, which retain the morphology of the TiO2 precursors, and the diameter of the microsphere is approximately
700 nm. The SEM image with high magnification (the inset of Fig. 4b) further demonstrated that the microflowers were tight assemblies of many nanosheets, which indicates the potential generally method to obtain similarly shaped perovskite titanate through A-site ion-exchange reactions with the spherical TiO2 precursors.
4. Conclusions In summary, hierarchical structured spherical TiO2 particles can be fabricated by means of a relatively straightforward in situ solvothermal reaction, using amorphous spherical TiO2 precursors as templates. By adjusting reaction parameters, the 3D hierarchical morphology of TiO2 microstructures can be controlled to obtain lychee-like or orange peel-like surface structure. The enhanced photocatalytic activities of different hierarchical structures of spherical TiO2 can be ascribed to the enhanced BET surface area and good crystallinity. The method presented here may be extended to synthesis other hierarchical morphologies of TiO2 using amorphous TiO2 with a different microscale morphology. Furthermore, using TiO2 as both template and reactant, we could obtain the hierarchical morphology of SrTiO3 perovskite structured particles for various applications.
Fig. 4. XRD patterns and SEM image of the prepared crystals. (a) XRD of TiO2 and SrTiO3, (b) SEM image of the SrTiO3.
Please cite this article as: Zhao W, et al. Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis. Mater Lett (2015), http://dx.doi.org/10.1016/j.matlet.2015.05.131i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
W. Zhao et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Acknowledgements Financial support from the National Natural Science Foundation of China (Grant no. 51202156) is gratefully acknowledged.
References [1] Sang LX, Zhao YX, Clemens B. Chem. Rev. 2014;114:9283–318. [2] Lv XJ, Mou XL, Wang YM, Huang FQ, Xu FF. Adv. Mater. 2010;22:3719–22. [3] Fujishima A, Honda K. Nature 1972;238:37–8.
[4] Lei BX, Zeng LL, Zhang P, Qiao HK, Sun ZF. J. Power Sources 2014;253:269–75. [5] Sun WW, Sun K, Peng T, You SJ, Liu HM, Liang LL, et al. J. Power Sources 2014;262:86–92. [6] Zhu TJ, Li J, Wu QS, Appl Mater ACS. Interfaces 2011;3:3448–53. [7] Alamgir Khan W, Ahmad S, Naqvi AH. Mater. Lett. 2014;133:28–31. [8] Calatayud DG, Jardiel T, Peiteado M, Caballero AC, Fernández-Hevia D. Nanoscale Res. Lett. 2014;9:273–7. [9] Liu RZ, Zhao YJ, Zhou HP. Adv. Powder Technol. 2014;25:780–6. [10] Zhao W, Jia Z, L E, Wang LG, Li ZY, Dai YJ. J. Phys. Chem. Solids 2013;74:1604–7. [11] Sing K, Everett D, Haul R, Moscou L, Pierotti R, Rouquerol J, et al. Pure Appl. Chem. 1985;57:603–19. [12] Groen JC, Peffera LAA, Ramirez JP. Micropor. Mesopor. Mater. 2003;60:1–17.
Please cite this article as: Zhao W, et al. Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis. Mater Lett (2015), http://dx.doi.org/10.1016/j.matlet.2015.05.131i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Q1 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis Wei Zhao n, Hongxing Wang, Xiangning Feng, Yubo Zhang, Shimeng Zhang School of Material Science and Engineering, Tianjin Chengjian University, Jinjing Road 26, Xiqing district, Tianjin 300384, China
art ic l e i nf o
a b s t r a c t
Article history: Received 1 April 2015 Received in revised form 10 May 2015 Accepted 18 May 2015
Hierarchically structured spherical TiO2 particles were synthesized in a two-step process. Firstly, amorphous spherical TiO2 precursor particles with narrow size distribution and good dispersibility were obtained by hydrolysis from Ti(SO4)2 using polyvinylpyrrolidone (PVP) as surfactants. The surface microstructures of the TiO2 precursors were modified in different solvothermal conditions. The results showed that lychee-like TiO2 crystals were formed using dimethylformamide (DMF) and Ethylene glycol (EG) solvents by solvothermal treatment at 180 °C for 2 h. When choosing cetyltrimethylammonium bromide (CTAB) as the surfactant, TiO2 crystals with an orange peel-like surface were obtained. The hierarchically spherical TiO2 showed good photodegradation rate in methylene blue (MB) solution under UV irradiation. These amorphous spherical TiO2 particles are also the precursors to form the similarly shaped perovskite titanate through A-site ion-exchange reactions. & 2015 Elsevier B.V. All rights reserved.
Keywords: Solvothermal Structural Hierarchical TiO2 Photodegradation
1. Introduction The hierarchical nanostructures built from nanounits, such as nanoparticles, nanorods, nanowires and nanosheets exhibit unique physical and chemical properties. These materials, which are different from its building blocks, have been widely investigated [1,2]. TiO2 has been widely used in the fields of energy and environmental engineering since the discovery of the phenomenon of photocatalytic splitting of water on a TiO2 electrode in 1972 [3]. To make the best use of solar energy, hierarchical structured TiO2 with high stability, monodispersible nature, good crystallinity, and a large specific surface area is required to improve photocatalytic performance. Constructed assemblies of TiO2 micrometer-sized microspheres will allow the photocatalyst to be easily recovered from the working suspension after use, while the nanometer-sized building units provide a greater available surface area for dye loading. Sun [4] proposed a novel concept of TiO2 hierarchical spheres for high efficiency dye-sensitised solar cells, which showed superior light-scattering capacity and faster charge transport for efficient charge collection. Researchers have carried out studies on different hierarchical TiO2 structures [5–8]. Despite the reasonable power conversion efficiency achieved with these TiO2 hierarchical microspheres, most synthesis processes on that have poor control over the morphology and density of the branches, affecting the n
Corresponding author. Fax: þ 86 2223085110. E-mail address: [email protected] (W. Zhao).
photonic properties. Herein, we report a solvothermal method that provides a facile way to control the hierarchical structured TiO2 in a predictable manner. The obtained products show large specific surface area and good photocatalytic activities.
2. Experimental details Amorphous spherical TiO2 particles were prepared by controlling the hydrolysis of Ti (SO4)2 in a manner that has been previously reported [9]. Typically, the solution of Ti (SO4)2 (4 mmol) in 75 mL de-ionized water was mixed with PVP (2.0 g), 1-propanol (75 mL). The mixture was stirred for 3 h at 70 °C and then washed and aged in the 1 mol/L alkaline solution. 0.4 g dried amorphous TiO2 particles were redispersed in 10 mL de-ionized water and mixed with one of three solutions (10 mL DMF, 0.1 g CTAB in 10 mL de-ionized water, or 10 mL EG). The mixture was transferred into a 25 mL Teflon-lined stainless steel autoclave, sealed and heated to 180 °C for 2 h. After the reaction, the product was washed with de-ionized water and ethanol to remove any residue, and then dried in an oven at 60 °C for 4 h. For further research, the metal salt Sr (NO3)2 was added into the EG and water solvents to provide A-site ions for the ion-exchange reaction to form perovskite titanate (SrTiO3), the atomic ratio of Sr to Ti is 2:1. Structural and Morphological investigations of the samples were recorded on a Rigaku 2500 powder X-ray diffractometer with Cu Kα (λ ¼0.15406 nm) and a field-emission scanning electron
http://dx.doi.org/10.1016/j.matlet.2015.05.131 0167-577X/& 2015 Elsevier B.V. All rights reserved.
Please cite this article as: Zhao W, et al. Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis. Mater Lett (2015), http://dx.doi.org/10.1016/j.matlet.2015.05.131i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
W. Zhao et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
2
microscope (FE-SEM LEO-1530). The BET test was carried on the surface area and pore-size analyzer (Quantachrome Nova stationA 3200). The photocatalytic activity of the synthesized powders were investigated using Vis spectrophotometer (7230G, Shanghai) by the photodegradation of MB (20 mg/L), under UV irradiation (λ ¼365 nm) using a method we reported in a previous study [10].
3. Results and discussion Fig. 1 shows the morphologies of TiO2 with different surface modifications. Each top right inset is an enlarged detail of the corresponding image. All images show similar good disperse microspheres. The amorphous TiO2 precursor particles with an average diameter of 700 nm in Fig. 1a exhibit a smoother surface compared with other samples. Fig. 1b is the TiO2 hydrothermally treated in the mixed solution of de-ionized water and DMF (the volume ratio is 1:1), which showed lychee-like microcrystals with a spherical shape, and the microspheres are composed of nanoparticles distributed uniformly over the surface. The microspheres in Fig.1c also illustrated the lychee-like morphology in EG solvothermal reaction. The hierarchical nanostructures, however, was not as homogenous as the DMF one. When choosing CTAB as the surfactant in the hydrothermal treatment, TiO2 crystals with orange peel-like surfaces are obtained (Fig. 1d). Fig. 2 shows the photocatalytic activities of TiO2, with the modifications using DMF, CTAB, and EG, after the dark absorption for the hierarchical TiO2, the degree of MB degradation under 60 min of UV light irradiation is about 100%, 100%, and 93%, respectively. The lychee-like TiO2 microspheres in the DMF solvothermal treatment show the highest activity, as they could photodegrade the MB in 45 min under UV light. The color of MB solution fades away in the presence of the TiO2 with orange peel-like surface (CTAB sample)
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
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Time (min) Fig. 2. The photodegradation of MB in the presence of different preparations of TiO2.
and another lychee-like surface (EG sample) in 1 h. The amorphous TiO2 absorbs MB during the dark reaction and then behaves similar with the blank sample, which indicates the amorpous TiO2 particles have little photocatylic activities. These findings show that hierarchically structured TiO2 products with high specific surface area not only retain the benefits of the crystalline TiO2 for photocatalytic processes; additionally, the introduction of microstructures appearing on the surface of microparticles can enhance the optical absorption and active sites. N2 adsorption–desorption isotherms and pore-size distribution curves of TiO2 are shown in Fig. 3. According to the International
Fig. 1. SEM images of TiO2 with different modifications (a) amorphous particles (b) DMF (c) EG and (d) CTAB.
Please cite this article as: Zhao W, et al. Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis. Mater Lett (2015), http://dx.doi.org/10.1016/j.matlet.2015.05.131i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
W. Zhao et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Fig. 3. N2 adsorption–desorption isotherms and corresponding pore size distribution curves of TiO2 samples with different modifications by (a) EG, (b) DMF, and (c) CTAB.
Union of Pure and Applied Chemistry (IUPAC) classification, all the isotherms belong to type IV, indicating that the samples possess porous structures [11]. For the representative sample a (Fig. 3a), the adsorption amount increases monotonously at a high P/P0 (P/ P0 40.9) without an adsorption limitation, suggesting that large pores formed primarily as a result of the aggregation of large particles. In samples b and c, an N2 adsorption–desorption hysteresis loop occurs in the P/P0 ¼0.4-0.8 range, which is indicative of a typical mesoporous material [12]. From the N2 desorption branch, the Barrett–Joyner–Halenda (BJH) average pore width of sample b was about 3.1 nm, the narrow distribution centered on 5 nm. No peaks exist in the curves of sample a and sample c in Fig.3b, suggesting the existence of macropores. The calculated Brunauer–Emmett–Teller (BET) surface areas are 5.84, 39.3, 106.7, and 109.4 m2/g for the amorphous TiO2 and TiO2 modified with EG, DMF, and CTAB, respectively. The results show that the DMF one with large BET surface and homogeneous morphology showed good photodegradation on the MB, which confirms the results of the photocatalytic activities. The XRD pattern of TiO2 modified with DMF is shown in Fig. 4a, the positions of diffraction peaks matched the anatase TiO2 (JCPDS no. 21-1272). After further treatment with the Sr resources, SrTiO3 was obtained (No. 35-0734, in Fig.4a). As shown in Fig. 4b, hierarchical flower-like SrTiO3 with 3D frameworks directly grows on the microspheres, which retain the morphology of the TiO2 precursors, and the diameter of the microsphere is approximately
700 nm. The SEM image with high magnification (the inset of Fig. 4b) further demonstrated that the microflowers were tight assemblies of many nanosheets, which indicates the potential generally method to obtain similarly shaped perovskite titanate through A-site ion-exchange reactions with the spherical TiO2 precursors.
4. Conclusions In summary, hierarchical structured spherical TiO2 particles can be fabricated by means of a relatively straightforward in situ solvothermal reaction, using amorphous spherical TiO2 precursors as templates. By adjusting reaction parameters, the 3D hierarchical morphology of TiO2 microstructures can be controlled to obtain lychee-like or orange peel-like surface structure. The enhanced photocatalytic activities of different hierarchical structures of spherical TiO2 can be ascribed to the enhanced BET surface area and good crystallinity. The method presented here may be extended to synthesis other hierarchical morphologies of TiO2 using amorphous TiO2 with a different microscale morphology. Furthermore, using TiO2 as both template and reactant, we could obtain the hierarchical morphology of SrTiO3 perovskite structured particles for various applications.
Fig. 4. XRD patterns and SEM image of the prepared crystals. (a) XRD of TiO2 and SrTiO3, (b) SEM image of the SrTiO3.
Please cite this article as: Zhao W, et al. Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis. Mater Lett (2015), http://dx.doi.org/10.1016/j.matlet.2015.05.131i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
W. Zhao et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Acknowledgements Financial support from the National Natural Science Foundation of China (Grant no. 51202156) is gratefully acknowledged.
References [1] Sang LX, Zhao YX, Clemens B. Chem. Rev. 2014;114:9283–318. [2] Lv XJ, Mou XL, Wang YM, Huang FQ, Xu FF. Adv. Mater. 2010;22:3719–22. [3] Fujishima A, Honda K. Nature 1972;238:37–8.
[4] Lei BX, Zeng LL, Zhang P, Qiao HK, Sun ZF. J. Power Sources 2014;253:269–75. [5] Sun WW, Sun K, Peng T, You SJ, Liu HM, Liang LL, et al. J. Power Sources 2014;262:86–92. [6] Zhu TJ, Li J, Wu QS, Appl Mater ACS. Interfaces 2011;3:3448–53. [7] Alamgir Khan W, Ahmad S, Naqvi AH. Mater. Lett. 2014;133:28–31. [8] Calatayud DG, Jardiel T, Peiteado M, Caballero AC, Fernández-Hevia D. Nanoscale Res. Lett. 2014;9:273–7. [9] Liu RZ, Zhao YJ, Zhou HP. Adv. Powder Technol. 2014;25:780–6. [10] Zhao W, Jia Z, L E, Wang LG, Li ZY, Dai YJ. J. Phys. Chem. Solids 2013;74:1604–7. [11] Sing K, Everett D, Haul R, Moscou L, Pierotti R, Rouquerol J, et al. Pure Appl. Chem. 1985;57:603–19. [12] Groen JC, Peffera LAA, Ramirez JP. Micropor. Mesopor. Mater. 2003;60:1–17.
Please cite this article as: Zhao W, et al. Control over the morphology of TiO2 hierarchically structured microspheres in solvothermal synthesis. Mater Lett (2015), http://dx.doi.org/10.1016/j.matlet.2015.05.131i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132