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Ultrathin Na2Ti9O19 heterostructural nanosheets modified with TiO2 nanoparticles for enhanced photocatalysis
Materials Letters 178 (2016) 140–143
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Ultrathin Na2Ti9O19 heterostructural nanosheets modified with TiO2 nanoparticles for enhanced photocatalysis Xiangzhuo Wang, Yan Li, Chengwei Wang n, Tian Gan, Jianjun Yan, Jian Wang Key Laboratory of Atomic and Molecular Physics & Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
art ic l e i nf o
a b s t r a c t
Article history: Received 29 January 2016 Received in revised form 15 April 2016 Accepted 29 April 2016 Available online 29 April 2016
TiO2 nanoparticles (TNPs) modified ultrathin Na2Ti9O19 heterostructural nanosheets arrays are successfully synthesized by novel two-step hydrothermal growth method. Our investigation of their photocatalytic degradation methyl orange (MO) under simulated sunlight irradiation suggests that TiO2@Na2Ti9O19 nanosheets possess dramatically enhanced photocatalytic activity, and their degradation efficiency is nearly 2.4 times higher than that of the pure Na2Ti9O19 nanosheets arrays for 2 h. After 4 cycles, their photocatalytic activities are kept almost unchanged, showing perfect reusability and superior stability, which would be attributed to their uniquely oriented heterostructural nanosheet arrays, matched energy level structure, and intimate interface contact. & 2016 Elsevier B.V. All rights reserved.
Keywords: Titanate ultrathin nanosheets arrays Nanoparticles Crystal growth Thin films Photocatalytic property
1. Introduction Recently, sodium titanate nanomaterials have gained increasing interest due to their open-layered structure, strong oxidation capacity and mild environmental remediation capacity [1]. Various nanostructural sodium titanate photocatalysts in the state of powders [2,3], such as nanoparticles and nanobelts, have been fabricated by some sophisticated methods. However, single phase pure sodium titanate is hard to use for practical application in field of the photocatalytic degradation of organic contaminants [4], because of intrinsic limiting issues, such as low charge separation and transfer rates, sluggish surface redox reactions, and poor reusability or stability caused by catalyst aggregation. There are two approaches to improve the photocatalytic performance of sodium titanate. The first one is to manipulate the morphology of sodium titanate to increase specific surface area available to photocatalytic redox reactions, by preventing catalyst aggregation. The other approach is to narrow the band gap of sodium titanate by non-metal doping, similar-gap semiconductor coupling, and heterostructural compounding [5–7], etc. for enhancement of light harvesting and photogenerated electron-hole pairs’ generation, separation, and transmission. In this paper we report a novel strategy of two-step hydrothermal growth method for preparation of TNPs modified ultrathin Na2Ti9O19 n
Corresponding author. E-mail address: [email protected] (C. Wang).
http://dx.doi.org/10.1016/j.matlet.2016.04.206 0167-577X/& 2016 Elsevier B.V. All rights reserved.
heterostructural nanosheets arrays on Ti substrate. In comparison, oriented two-dimensional ultrathin sodium titanate nanosheets should be a more promising catalysts candidate for improvement of its photocatalytic activity, which is highly desirable to employ a facile and suitable procedure for synthesis of this heterostructure based on ultrathin nanosheets. After carefully comparative investigation of their photocatalytic degradation MO under simulated sunlight irradiation we found that the photocatalytic performances of the TNPs@Na2Ti9O19 nanosheets arrays are substantially improved.
2. Experimental section The preparation of Ti foils was similar to our previous process [8]. The first step, Ti foils was immersed in 2.5 M NaOH aqueous solution at 180 °C in autoclave for 24 h by hydrothermal treatment. Then, the as-prepared Na2Ti9O19 nanosheets arrays were annealed at 500 °C for 2.5 h in a quartz tube. Followed second step, TNPs modified ultrathin Na2Ti9O19 heterostructural nanosheets arrays were fabricated by the hydrothermal process in concentrated TiCl4 aqueous solution at 70 °C for 0.5 h. After that, the TNPs@Na2Ti9O19 nanosheets arrays were annealed in air conditions at 500 °C for 0.5 h. The surface morphologies, compositions, crystal structures, and absorption properties of all samples were characterized using scanning electron microscope (SEM, JSM-6701F), X-ray
X. Wang et al. / Materials Letters 178 (2016) 140–143
diffractometer (XRD, D/max-2400) and Raman spectroscopy (Horiba HR800), and UV–vis spectrophotometer (Perkin Elmer Lambda 900 spectrometer), respectively. Photoreaction system consists of a glass reactor and a simulated solar-light source (The light source was a 500 W Xe lamp (CHF-XM500, Beijing Trusttech Co., Ltd)). Similarly, UV–vis spectrophotometer was used to measure the absorption spectra of MO. Prior to photoreaction, the suspension was magnetically stirred in the dark for 30 min to establish an adsorption-desorption equilibrium between the TNPs@Na2Ti9O19 photocatalyst and MO.
3. Results and discussion Fig. 1(a) shows the schematic view of the two-step growth process of TNPs@Na2Ti9O19 nanosheets arrays. The typical SEM image of the sample obtained after the first step growth process shows that the Na2Ti9O19 nanosheets with smooth surface morphology are uniformly distributed, high-density, and vertically aligned arrayed nanostructures as seen in Fig. 1(b), from which the geometric parameters of the Na2Ti9O19 nanosheets can be estimated, their thickness, width and length are about 2–10 nm, 200– 300 nm, and a few microns, respectively. The Fig. 1(c) shows the morphology of TNPs@Na2Ti9O19 nanosheets arrays obtained after the second step growth process. It is clearly seen that no obvious change occurred in apparent morphology of the Na2Ti9O19 nanosheets but many TNPs deposited on their surfaces compared with Fig. 1(b). The inset of Fig. 1(c) further presents the high resolution SEM image of TNPs@Na2Ti9O19, which depicts a slight rough nanosheets morphology of the ultimate sample modified by the TNPs with a small size (2–10 nm). Thus, the TNPs@Na2Ti9O19 nanosheets arrays are uniformly distributed, high-density, and vertically aligned nanoarrays with large specific surface area, which should be conducive to the adsorption of organic contaminants for photocatalytic degradation. The crystal structure and possible phase evolution of the samples are illustrated by XRD patterns and Raman spectra as seen
141
in Fig. 2. Typical XRD diffraction patterns of the samples are shown in Fig. 2(a). Here two major diffraction peaks of (122) and (020) appear in both pure Na2Ti9O19 and TNPs@Na2Ti9O19 nanosheets arrays, which is consistent with the standard values of Na2Ti9O19 (JCPDS card 33–1293). For the TNPs@Na2Ti9O19, the diffraction peaks of (122) and (020) has no change compared with the pure Na2Ti9O19, indicating the crystal phase of Na2Ti9O19 was not destroyed after modification of TNPs. The emergence of a typical diffraction peak of TNPs, located at 2θ value of 25.3°, which is attributed to the anatase TNPs with specifically exposed {101} facets deposited on the external surface of Na2Ti9O19, and its crystallinity is very well. The Raman data in Fig. 2(b) exhibit four strong peaks at about 145, 396, 517 and 640 cm 1, indicating that surface of titanate is covered by TNPs [9]. Obviously, the Raman peaks of TNPs@Na2Ti9O19 are particularly strong, which further explains that TNPs and Na2Ti9O19 nanosheets have a good contact and form an excellent heterogeneous contacts between them, which would contribute to photogenerated carriers’ separation and transfer at their interfaces. UV–vis spectrum is used to evaluate the bandgap of the nanostructured TNPs@Na2Ti9O19 photocatalysts as shown by Fig. 3 (a). The absorption intensity of as-prepared samples is significantly enhanced after TNPs modification and the absorption edge exhibits an obvious red shift than pure Na2Ti9O19, this means that more light could be used by the heterostructure to take part in photocatalysis. According to Tauc's equation αhν ¼ A(hν-Eg)n/2, the direct band gap energies of samples are calculated [10]. The inset of Fig. 3(a) is the estimated bandgaps of Na2Ti9O19 (3.50 eV) and TNPs@Na2Ti9O19 (3.10 eV), which indicates the effective bandgap of the TNPs@Na2Ti9O19 heterostructure is narrowed and its photoabsorption region is obviously broadened, but here simulated sunlight irradiation at ultraviolet wavelengths would remain the major contribution to its photoreaction. For a better understanding the principle of effective bandgap narrowing in the TNPs@Na2Ti9O19, the schematic energy level diagram is illustrated in Fig. 3(b), where the matched energy level of the heterostructure would be beneficial for photo-induced charges separation and
Fig. 1. (a) Schematic diagram of the two-step growth process of TNPs@Na2Ti9O19 nanosheets arrays. Typical SEM images of the (b) Na2Ti9O19 and (c) TNPs@Na2Ti9O19 nanosheets arrays.
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Fig. 2. (a) XRD patterns and (b) Raman spectra of Na2Ti9O19 and TNPs@Na2Ti9O19.
Fig. 3. (a) Absorption spectra of Na2Ti9O19 and TNPs@Na2Ti9O19. The inset is the corresponding estimated band gap. (b) Schematic energy level diagram of TNPs@Na2Ti9O19. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)
transfer from TiO2 to Na2Ti9O19 via the interfaces between them, and could efficiently hinder the photo-induced electrons and holes recombination. Fig. 4(a) is the digital images of MO solutions under simulated sunlight irradiation with different degradation time by TNPs@Na2Ti9O19. It is clear that the MO solution was efficiently decolorized with the increase of degradation time. Fig. 4(b) shows the time-dependent absorption spectra of the MO solution corresponding to the Fig. 4(a). Fig. 4(c) is the photocatalytic activities of samples under the same conditions. The MO solution degradation is neglectable even under simulated sunlight irradiation without photocatalyst loading, while loading pure Na2Ti9O19 as photocatalyst, there is apparent degradation in the MO solution. More interestingly, The TNPs@Na2Ti9O19 possesses higher catalytic activity than the pure Na2Ti9O19, and their degradation efficiency is nearly 2.4 times higher than that of the pure Na2Ti9O19 for 2 h. In addition, the reusability and stability are very important for practical application of photocatalyst, so recycling degradation experiments were also investigated. After each cycle, the TNPs@Na2Ti9O19 were collected and washed with deionized water for several times and then reused for the next cycle. As shown in Fig. 4(d), the photocatalytic activities are kept almost unchanged after 4 cycles, indicating the good reusability and stability of the TNPs@Na2Ti9O19.
4. Conclusions In conclusion, we developed a simple and promising two-step hydrothermal growth method for preparation of TNPs modified ultrathin oriented Na2Ti9O19 heterostructural nanosheets arrays. And the characterization results revealed that the TNPs@Na2Ti9O19 nanosheets are uniformly distributed, high-density, highly crystalline, and vertically aligned nanoarrays with large specific surface area. After carefully comparative study of their photocatalytic degradation MO under simulated solar light sources irradiation we found that the TNPs@Na2Ti9O19 nanosheets arrays possessed dramatically enhanced photocatalytic activity, and their degradation efficiency was nearly 2.4 times higher than that of the pure Na2Ti9O19 nanosheets arrays for 2 h. After 4 cycles, their photocatalytic activities were kept almost unchanged, indicating the TNPs@Na2Ti9O19 nanosheets arrays possessed perfect reusability and superior stability, which would stem from their vertically oriented heterostructural nanosheet arrays, matched energy level structure, and intimate interface contact. These results presented herein indicate that the TNPs@Na2Ti9O19 nanosheets arrays would be an excellent candidate for photocatalytic application.
Acknowledgments This work was supported by the National Natural Science
X. Wang et al. / Materials Letters 178 (2016) 140–143
143
Fig. 4. (a) Digital photographs and (b) Absorption spectra of the MO with different degradation time by TNPs@Na2Ti9O19. (c) Photocatalytic degradation rate of MO for pure Na2Ti9O19 and TNPs@Na2Ti9O19 under simulated sunlight irradiation. (d) Reusability and stability of the TNPs@Na2Ti9O19.
Foundation of China (Grant Nos. 11474231, 11264034, 11364036, and 11464041) and the Fundamental Research Funds for the Universities of Gansu Province.
References [1] J.W. Liu, T. Ding, Z.H. Li, J.X. Zhao, S.Y. Li, J.H. Liu, Ceram. Int. 39 (2013) 8059–8063. [2] L.L. Marciniuk, P. Hammer, H.O. Pastore, U. Schuchardt, D. Cardoso, Fuel 118 (2014) 48–54.
[3] Y.C. Pu, Y.C. Chen, Y.J. Hsu, Appl. Catal. B: Environ. 97 (2010) 389–397. [4] C. Liu, T. Sun, L. Wu, J.Y. Liang, Q.J. Huang, J. Chen, W.H. Hou, Appl. Catal. B: Environ. 170–171 (2015) 17–24. [5] M.Y. Xing, W.K. Li, Y.M. Wu, J.L. Zhang, X.Q.J. Gong, C. Physical Chemistry, 115 (2011) 7858–7865. [6] Y.F. Cao, X.T. Li, Z.F. Bian, A. Fuhr, D.Q. Zhang, J. Zhu, Appl. Catal. B: Environ. 180 (2016) 551–558. [7] J.L. Li, X.J. Liu, Z. Sun, L.K. Pan, Colloid Interface Sci. 463 (2016) 145–153. [8] X.Q. Zhang, C.W. Wang, J.B. Chen, W.D. Zhu, A.Z. Liao, Y. Li, J. Wang, L. Ma, ACS Appl. Mater. Interfaces 6 (2014) 20625–20633. [9] X.Q. Zhang, J.B. Chen, S.Y. Li, A.Z. Liao, C.W. Wang, Mater. Lett. 144 (2015) 1–4. [10] Z.W. Pan, Y. Li, X. Hou, J.J. Yan, C.W. Wang, Physica E 63 (2014) 1–7.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Ultrathin Na2Ti9O19 heterostructural nanosheets modified with TiO2 nanoparticles for enhanced photocatalysis Xiangzhuo Wang, Yan Li, Chengwei Wang n, Tian Gan, Jianjun Yan, Jian Wang Key Laboratory of Atomic and Molecular Physics & Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
art ic l e i nf o
a b s t r a c t
Article history: Received 29 January 2016 Received in revised form 15 April 2016 Accepted 29 April 2016 Available online 29 April 2016
TiO2 nanoparticles (TNPs) modified ultrathin Na2Ti9O19 heterostructural nanosheets arrays are successfully synthesized by novel two-step hydrothermal growth method. Our investigation of their photocatalytic degradation methyl orange (MO) under simulated sunlight irradiation suggests that TiO2@Na2Ti9O19 nanosheets possess dramatically enhanced photocatalytic activity, and their degradation efficiency is nearly 2.4 times higher than that of the pure Na2Ti9O19 nanosheets arrays for 2 h. After 4 cycles, their photocatalytic activities are kept almost unchanged, showing perfect reusability and superior stability, which would be attributed to their uniquely oriented heterostructural nanosheet arrays, matched energy level structure, and intimate interface contact. & 2016 Elsevier B.V. All rights reserved.
Keywords: Titanate ultrathin nanosheets arrays Nanoparticles Crystal growth Thin films Photocatalytic property
1. Introduction Recently, sodium titanate nanomaterials have gained increasing interest due to their open-layered structure, strong oxidation capacity and mild environmental remediation capacity [1]. Various nanostructural sodium titanate photocatalysts in the state of powders [2,3], such as nanoparticles and nanobelts, have been fabricated by some sophisticated methods. However, single phase pure sodium titanate is hard to use for practical application in field of the photocatalytic degradation of organic contaminants [4], because of intrinsic limiting issues, such as low charge separation and transfer rates, sluggish surface redox reactions, and poor reusability or stability caused by catalyst aggregation. There are two approaches to improve the photocatalytic performance of sodium titanate. The first one is to manipulate the morphology of sodium titanate to increase specific surface area available to photocatalytic redox reactions, by preventing catalyst aggregation. The other approach is to narrow the band gap of sodium titanate by non-metal doping, similar-gap semiconductor coupling, and heterostructural compounding [5–7], etc. for enhancement of light harvesting and photogenerated electron-hole pairs’ generation, separation, and transmission. In this paper we report a novel strategy of two-step hydrothermal growth method for preparation of TNPs modified ultrathin Na2Ti9O19 n
Corresponding author. E-mail address: [email protected] (C. Wang).
http://dx.doi.org/10.1016/j.matlet.2016.04.206 0167-577X/& 2016 Elsevier B.V. All rights reserved.
heterostructural nanosheets arrays on Ti substrate. In comparison, oriented two-dimensional ultrathin sodium titanate nanosheets should be a more promising catalysts candidate for improvement of its photocatalytic activity, which is highly desirable to employ a facile and suitable procedure for synthesis of this heterostructure based on ultrathin nanosheets. After carefully comparative investigation of their photocatalytic degradation MO under simulated sunlight irradiation we found that the photocatalytic performances of the TNPs@Na2Ti9O19 nanosheets arrays are substantially improved.
2. Experimental section The preparation of Ti foils was similar to our previous process [8]. The first step, Ti foils was immersed in 2.5 M NaOH aqueous solution at 180 °C in autoclave for 24 h by hydrothermal treatment. Then, the as-prepared Na2Ti9O19 nanosheets arrays were annealed at 500 °C for 2.5 h in a quartz tube. Followed second step, TNPs modified ultrathin Na2Ti9O19 heterostructural nanosheets arrays were fabricated by the hydrothermal process in concentrated TiCl4 aqueous solution at 70 °C for 0.5 h. After that, the TNPs@Na2Ti9O19 nanosheets arrays were annealed in air conditions at 500 °C for 0.5 h. The surface morphologies, compositions, crystal structures, and absorption properties of all samples were characterized using scanning electron microscope (SEM, JSM-6701F), X-ray
X. Wang et al. / Materials Letters 178 (2016) 140–143
diffractometer (XRD, D/max-2400) and Raman spectroscopy (Horiba HR800), and UV–vis spectrophotometer (Perkin Elmer Lambda 900 spectrometer), respectively. Photoreaction system consists of a glass reactor and a simulated solar-light source (The light source was a 500 W Xe lamp (CHF-XM500, Beijing Trusttech Co., Ltd)). Similarly, UV–vis spectrophotometer was used to measure the absorption spectra of MO. Prior to photoreaction, the suspension was magnetically stirred in the dark for 30 min to establish an adsorption-desorption equilibrium between the TNPs@Na2Ti9O19 photocatalyst and MO.
3. Results and discussion Fig. 1(a) shows the schematic view of the two-step growth process of TNPs@Na2Ti9O19 nanosheets arrays. The typical SEM image of the sample obtained after the first step growth process shows that the Na2Ti9O19 nanosheets with smooth surface morphology are uniformly distributed, high-density, and vertically aligned arrayed nanostructures as seen in Fig. 1(b), from which the geometric parameters of the Na2Ti9O19 nanosheets can be estimated, their thickness, width and length are about 2–10 nm, 200– 300 nm, and a few microns, respectively. The Fig. 1(c) shows the morphology of TNPs@Na2Ti9O19 nanosheets arrays obtained after the second step growth process. It is clearly seen that no obvious change occurred in apparent morphology of the Na2Ti9O19 nanosheets but many TNPs deposited on their surfaces compared with Fig. 1(b). The inset of Fig. 1(c) further presents the high resolution SEM image of TNPs@Na2Ti9O19, which depicts a slight rough nanosheets morphology of the ultimate sample modified by the TNPs with a small size (2–10 nm). Thus, the TNPs@Na2Ti9O19 nanosheets arrays are uniformly distributed, high-density, and vertically aligned nanoarrays with large specific surface area, which should be conducive to the adsorption of organic contaminants for photocatalytic degradation. The crystal structure and possible phase evolution of the samples are illustrated by XRD patterns and Raman spectra as seen
141
in Fig. 2. Typical XRD diffraction patterns of the samples are shown in Fig. 2(a). Here two major diffraction peaks of (122) and (020) appear in both pure Na2Ti9O19 and TNPs@Na2Ti9O19 nanosheets arrays, which is consistent with the standard values of Na2Ti9O19 (JCPDS card 33–1293). For the TNPs@Na2Ti9O19, the diffraction peaks of (122) and (020) has no change compared with the pure Na2Ti9O19, indicating the crystal phase of Na2Ti9O19 was not destroyed after modification of TNPs. The emergence of a typical diffraction peak of TNPs, located at 2θ value of 25.3°, which is attributed to the anatase TNPs with specifically exposed {101} facets deposited on the external surface of Na2Ti9O19, and its crystallinity is very well. The Raman data in Fig. 2(b) exhibit four strong peaks at about 145, 396, 517 and 640 cm 1, indicating that surface of titanate is covered by TNPs [9]. Obviously, the Raman peaks of TNPs@Na2Ti9O19 are particularly strong, which further explains that TNPs and Na2Ti9O19 nanosheets have a good contact and form an excellent heterogeneous contacts between them, which would contribute to photogenerated carriers’ separation and transfer at their interfaces. UV–vis spectrum is used to evaluate the bandgap of the nanostructured TNPs@Na2Ti9O19 photocatalysts as shown by Fig. 3 (a). The absorption intensity of as-prepared samples is significantly enhanced after TNPs modification and the absorption edge exhibits an obvious red shift than pure Na2Ti9O19, this means that more light could be used by the heterostructure to take part in photocatalysis. According to Tauc's equation αhν ¼ A(hν-Eg)n/2, the direct band gap energies of samples are calculated [10]. The inset of Fig. 3(a) is the estimated bandgaps of Na2Ti9O19 (3.50 eV) and TNPs@Na2Ti9O19 (3.10 eV), which indicates the effective bandgap of the TNPs@Na2Ti9O19 heterostructure is narrowed and its photoabsorption region is obviously broadened, but here simulated sunlight irradiation at ultraviolet wavelengths would remain the major contribution to its photoreaction. For a better understanding the principle of effective bandgap narrowing in the TNPs@Na2Ti9O19, the schematic energy level diagram is illustrated in Fig. 3(b), where the matched energy level of the heterostructure would be beneficial for photo-induced charges separation and
Fig. 1. (a) Schematic diagram of the two-step growth process of TNPs@Na2Ti9O19 nanosheets arrays. Typical SEM images of the (b) Na2Ti9O19 and (c) TNPs@Na2Ti9O19 nanosheets arrays.
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Fig. 2. (a) XRD patterns and (b) Raman spectra of Na2Ti9O19 and TNPs@Na2Ti9O19.
Fig. 3. (a) Absorption spectra of Na2Ti9O19 and TNPs@Na2Ti9O19. The inset is the corresponding estimated band gap. (b) Schematic energy level diagram of TNPs@Na2Ti9O19. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)
transfer from TiO2 to Na2Ti9O19 via the interfaces between them, and could efficiently hinder the photo-induced electrons and holes recombination. Fig. 4(a) is the digital images of MO solutions under simulated sunlight irradiation with different degradation time by TNPs@Na2Ti9O19. It is clear that the MO solution was efficiently decolorized with the increase of degradation time. Fig. 4(b) shows the time-dependent absorption spectra of the MO solution corresponding to the Fig. 4(a). Fig. 4(c) is the photocatalytic activities of samples under the same conditions. The MO solution degradation is neglectable even under simulated sunlight irradiation without photocatalyst loading, while loading pure Na2Ti9O19 as photocatalyst, there is apparent degradation in the MO solution. More interestingly, The TNPs@Na2Ti9O19 possesses higher catalytic activity than the pure Na2Ti9O19, and their degradation efficiency is nearly 2.4 times higher than that of the pure Na2Ti9O19 for 2 h. In addition, the reusability and stability are very important for practical application of photocatalyst, so recycling degradation experiments were also investigated. After each cycle, the TNPs@Na2Ti9O19 were collected and washed with deionized water for several times and then reused for the next cycle. As shown in Fig. 4(d), the photocatalytic activities are kept almost unchanged after 4 cycles, indicating the good reusability and stability of the TNPs@Na2Ti9O19.
4. Conclusions In conclusion, we developed a simple and promising two-step hydrothermal growth method for preparation of TNPs modified ultrathin oriented Na2Ti9O19 heterostructural nanosheets arrays. And the characterization results revealed that the TNPs@Na2Ti9O19 nanosheets are uniformly distributed, high-density, highly crystalline, and vertically aligned nanoarrays with large specific surface area. After carefully comparative study of their photocatalytic degradation MO under simulated solar light sources irradiation we found that the TNPs@Na2Ti9O19 nanosheets arrays possessed dramatically enhanced photocatalytic activity, and their degradation efficiency was nearly 2.4 times higher than that of the pure Na2Ti9O19 nanosheets arrays for 2 h. After 4 cycles, their photocatalytic activities were kept almost unchanged, indicating the TNPs@Na2Ti9O19 nanosheets arrays possessed perfect reusability and superior stability, which would stem from their vertically oriented heterostructural nanosheet arrays, matched energy level structure, and intimate interface contact. These results presented herein indicate that the TNPs@Na2Ti9O19 nanosheets arrays would be an excellent candidate for photocatalytic application.
Acknowledgments This work was supported by the National Natural Science
X. Wang et al. / Materials Letters 178 (2016) 140–143
143
Fig. 4. (a) Digital photographs and (b) Absorption spectra of the MO with different degradation time by TNPs@Na2Ti9O19. (c) Photocatalytic degradation rate of MO for pure Na2Ti9O19 and TNPs@Na2Ti9O19 under simulated sunlight irradiation. (d) Reusability and stability of the TNPs@Na2Ti9O19.
Foundation of China (Grant Nos. 11474231, 11264034, 11364036, and 11464041) and the Fundamental Research Funds for the Universities of Gansu Province.
References [1] J.W. Liu, T. Ding, Z.H. Li, J.X. Zhao, S.Y. Li, J.H. Liu, Ceram. Int. 39 (2013) 8059–8063. [2] L.L. Marciniuk, P. Hammer, H.O. Pastore, U. Schuchardt, D. Cardoso, Fuel 118 (2014) 48–54.
[3] Y.C. Pu, Y.C. Chen, Y.J. Hsu, Appl. Catal. B: Environ. 97 (2010) 389–397. [4] C. Liu, T. Sun, L. Wu, J.Y. Liang, Q.J. Huang, J. Chen, W.H. Hou, Appl. Catal. B: Environ. 170–171 (2015) 17–24. [5] M.Y. Xing, W.K. Li, Y.M. Wu, J.L. Zhang, X.Q.J. Gong, C. Physical Chemistry, 115 (2011) 7858–7865. [6] Y.F. Cao, X.T. Li, Z.F. Bian, A. Fuhr, D.Q. Zhang, J. Zhu, Appl. Catal. B: Environ. 180 (2016) 551–558. [7] J.L. Li, X.J. Liu, Z. Sun, L.K. Pan, Colloid Interface Sci. 463 (2016) 145–153. [8] X.Q. Zhang, C.W. Wang, J.B. Chen, W.D. Zhu, A.Z. Liao, Y. Li, J. Wang, L. Ma, ACS Appl. Mater. Interfaces 6 (2014) 20625–20633. [9] X.Q. Zhang, J.B. Chen, S.Y. Li, A.Z. Liao, C.W. Wang, Mater. Lett. 144 (2015) 1–4. [10] Z.W. Pan, Y. Li, X. Hou, J.J. Yan, C.W. Wang, Physica E 63 (2014) 1–7.