Enhanced Photocatalytic Activity of W-Doped and W-La-Codoped TiO<sub>2</sub> Nanomaterials under Simulated Sunlight

Hua, Chenghe; Dong, Xiaoli; Wang, Xiuying; Xue, Mang; Zhang, Xiufang; Ma, Hongchao

doi:https://doi.org/10.1155/2014/943796

Journal of Nanomaterials

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Abstract Introduction Results and Discussion Conclusions Acknowledgments References Copyright Related Articles

Research Article | Open Access

Volume 2014 | Article ID 943796 | https://doi.org/10.1155/2014/943796

Enhanced Photocatalytic Activity of W-Doped and W-La-Codoped TiO₂ Nanomaterials under Simulated Sunlight

Chenghe Hua,¹Xiaoli Dong,¹Xiuying Wang,²Mang Xue,¹Xiufang Zhang,¹and Hongchao Ma¹

Academic Editor: Yuekun Lai

Received10 Jul 2014

Revised29 Aug 2014

Accepted30 Aug 2014

Published21 Oct 2014

Abstract

W-doped TiO₂ and W-La-codoped TiO₂ nanomaterials were successfully synthesized via the sol-gel method. The products were characterized by X-ray diffraction, UV-vis diffuse reflectance spectrophotometer, transmission electron microscopy, and X-ray photoelectron spectroscopy. The presence of W and La results in significant red shift of absorption edge for TiO₂-based nanomaterials. The weight ratios of La and W in the composites play important roles in the absorption edge for TiO₂-based nanomaterials. The photocatalytic activities of both W-doped TiO₂ and W-La-codoped TiO₂ photocatalysts for decolorization of methyl orange solution were evaluated under simulated sunlight irradiation. The results showed that both W-doped and W-La-codoped can effectively improve the photocatalytic behaviors of TiO₂ nanomaterials ascribed to the improved photoinduced charge carriers separation, enhanced light absorption, and large surface area. Furthermore, W-La-codoped TiO₂ exhibited higher photocatalytic activity than W-doped TiO₂. Considering their high photocatalytic activity, the doped TiO₂ nanomaterials could be applied in wastewater treatment and environmental purification.

1. Introduction

Nowadays, in view of the increasing awareness on environmental pollution, application of semiconductor photocatalysis for chemical wastes treatment has been considered as a promising approach and attracted extensive attention [1–10]. A series of semiconductors has been successfully used as photocatalysts, including oxides and sulfides [11–16]. Among these semiconductors, TiO₂ is especially attractive because of its high photocatalytic activity, excellent chemical stability, nontoxicity, and low cost, making it potentially suitable for conversion of solar energy to electricity or chemical energy [17–21]. However, TiO₂ with large energy bandgap of 3.2 eV can be only excited by UV light, which merely occupies about 4% of solar energy. It leads to the less utilization of solar energy and inhibits the practical application of TiO₂ under sunlight. Aiming at solving this shortcoming, many approaches have been successfully reported to make TiO₂-based materials respond to visible light, such as composite semiconductors, transition metal doping, and noble metal deposition [22–29]. Among these methods, transition metal doping is usually considered to be one of the most effective strategies for improving the photocatalytic activity of TiO₂ under visible light. The construction of doped TiO₂ materials introduces additional electronic states within the bandgap, leading to an extension of light absorption in the visible region. In addition, doped TiO₂ materials increase the lifetime of photoinduced charge carriers by bandgap irradiation, thereby leading to enhancement of photocatalytic efficiency [25]. Palmisano has investigated the influence of a series of transition metal ions (Co, Cr, Cu, Fe, Mo, V, and W) on the photocatalytic activity of TiO₂. The results show that only W-doping distinctly enhances the photocatalytic activity of TiO₂ under visible light irradiation [26]. In addition, rare earth metals can also be used to enhance the visible light photocatalytic activity of TiO₂ [30–34]. Although single metal ion doped TiO₂ has been widely investigated, the utilization of two-metal-ion codoped TiO₂ as a visible light photocatalyst has not been adequately investigated.

In this paper, both W-doped and W-La-codoped TiO₂ nanomaterials have been successfully synthesized via a sol-gel method. The results show that the existence of W and La in the nanomaterials can effectively enhance the photocatalytic behaviors of TiO₂ for decolorization of methyl orange solution under simulated sunlight irradiation. It is mainly attributed to the improved photoinduced charge carriers separation, enhanced light absorption, and large surface area.

2. Experimental Section

2.1. Materials

Anhydrous ethanol (C₂H₅OH, AR), tetrabutyl titanate (TBOT, CP), acetic acid (CH₃COOH, AR), ammonium tungstate hydrate , lanthanum nitrate hexahydrate , methyl orange (MO, AR), and nitric acid (HNO₃, GR, 65–68 wt%) were used without further purification.

2.2. Preparation of W-Doped TiO₂ Nanomaterials

Firstly, a sol-gel solution, denoted by solution A, was prepared by dispersing 17 mL of TBOT and 0.2 mL of HNO₃ in 40 mL of C₂H₅OH with ultrasonic vibration for 30 min. Another solution, denoted by solution B, was prepared by mixing 4 mL of deionized water, 5 mL of CH₃COOH, and 20 mL of C₂H₅OH. Then, solution B was added dropwise into solution A under vigorous stirring. Subsequently, a certain amount of (NH₄)₁₀W₁₂O₄₁ solution with the concentration of 20 was added to the above solution under vigorous stirring. The solution was aged at room temperature for 5 h and the precursor gel was obtained. Finally, the gel was dried at 100°C for 6 h, grinded, and calcined at 400°C for 3 h in air. The weight ratio of W in the catalysts could be easily controlled by adjusting the amount of (NH₄)₁₀W₁₂O₄₁ solution. The obtained samples with different weight ratio of W to Ti (0, 0.4%, 0.6%, 0.8%, 1%, and 1.2%) were denoted by TiO₂, 0.4% W/TiO₂, 0.6% W/TiO₂, 0.8% W/TiO₂, 1.0% W/TiO₂, and 1.2% W/TiO₂, respectively.

2.3. Preparation of W-La-Codoped TiO₂ Nanomaterials

The synthesis of W-La-codoped TiO₂ nanomaterials was similar to that of 0.8% W/TiO₂ nanomaterials, except that solution B was added to different amount of to make the weight ratio of La to Ti be 1%, 2%, 3%, 4%, and 5%. These samples were denoted by 1% La/W/TiO₂, 2% La/W/TiO₂, 3% La/W/TiO₂, 4% La/W/TiO₂, and 5% La/W/TiO₂, respectively.

2.4. Characterization

The samples were examined by X-ray diffraction (XRD) on a Shimadzu XRD-6100 diffractometer with Cu Kα radiation ( nm), operating at 40 kV and 100 mA. The diffused reflectance UV-visible spectra (DRS) were recorded on a CARY 100 CONC spectrometer. Transmission electron microscopy (TEM) was carried out with a JEOL JEM-2000EX operating at 200 kV. X-ray photoelectron spectra (XPS) were recorded with a VG Scientific ESCALAB250 XPS instrument. The C(1s) level was used as an internal reference at 284.6 eV. Energy dispersive X-ray spectroscopy (EDS) was recorded with Oxford INCA. The N₂ adsorption-desorption was measured by JW-BK222 nitrogen adsorption analyzer. Photoluminescence (PL) spectra were recorded by fluorescence spectroscopy (LS55) with the excitation wavelength of 280 nm.

2.5. Photocatalytic Decolorization of MO Solution

The photocatalytic activities were evaluated by photodecolorization of MO solution with at 30°C. In this case, a 350 W xenon lamp was used as a light source. 200 mg of photocatalyst was added to 200 mL of MO solution with the initial concentration of 20 and then magnetically stirred in the dark for 20 min to ensure the establishment of an adsorption-desorption equilibrium and uniform distribution. The suspensions were collected every 20 min and centrifuged to separate the photocatalyst particles. The MO concentration was determined by monitoring the absorbance peak at nm using a Shimadzu, UV-1600 (PC) UV-visible spectrophotometer.

3. Results and Discussion

Figure 1 shows the XRD patterns of the as-synthesized W-doped TiO₂ and W-La-codoped TiO₂. It can be seen that all of the diffraction peaks are ascribed to anatase TiO₂ and no peaks indexed to WO₃ and La₂O₃ are detected, indicating that crystalline WO₃ and La₂O₃ are not formed in this case. According to previous report [35], W⁶⁺ should be present in substitutional positions of Ti⁴⁺ in the lattice of TiO₂ due to the similar ionic radii between W⁶⁺ and Ti⁴⁺. However, it seems difficult for La³⁺ to be incorporated into the lattice of TiO₂ due to the mismatch of the ionic radii of Ti⁴⁺ and La³⁺, and it may exist in the form of La₂O₃ which was very small and highly dispersed in the composites [31, 36]. In addition, the broadened peaks suggest that the samples are composed of nanosized particles.

(a)

(b)

XPS analysis is performed to identify the chemical composition of the W-La-codoped TiO₂. The XPS spectrum for 4% La/W/TiO₂ shown in Figure 2(a) displays the corresponding peaks of O1s, Ti2p, C1s, W4f, and La3d, indicating the existence of W and La in the composite. The spectrum in Figure 2(b) shows two peaks locating at 458.9 and 464.4 eV, arising from the spin-orbit splitting of the Ti2p components, namely, Ti2p_3/2 and Ti2p_1/2, which are in good agreement with those of titanium dioxide [37]. Figure 2(c) exhibits the W4f_7/2 core level binding energy peak at 36.7 eV, which is consistent with that of tungsten trioxide [38]. The weak peak located at 835 eV in Figure 2(d) is related to La3d components (La3d_5/2). For further confirming the existence of W and La, EDS has also been performed (Figure 3). It can be clearly seen that the signals for W are present in W-doped TiO₂ nanomaterials, and the weight ratio of W/Ti is consistent with what we proposed. Similarly, W and La signals also appeared in the EDS spectrum of W-La-codoped TiO₂, illustrating the existence of W and La.

(a)

(b)

(c)

(d)

(a)

(b)

In order to study the morphology of the obtained samples, TEM is performed. As shown in Figure 4(a), pure TiO₂ are composed of small nanoparticles with the diameter in the range of 15–30 nm. However, both W-doped TiO₂ and W-La-codoped TiO₂ consist of small nanoparticles, which are uniform with the main diameter of approximately 10 and 8 nm, respectively. It is attributed to the presence of W and La in the composites, which can inhibit the growth of TiO₂ nanoparticles [36, 39, 40]. This is well consistent with the results of XRD studies. In HRTEM image, the fringe spacing of 0.35 nm can be indexed to the (101) plane of anatase TiO₂, indicating well crystalline TiO₂ nanoparticles are formed in this case.

(a)

(b)

(c)

(d)

Figure 5(a) shows the UV-vis absorption spectra of the TiO₂ and W-doped TiO₂ nanomaterials with various amounts of W, converted from the corresponding diffuse reflectance spectra. It can be seen that pure TiO₂ nanomaterials only exhibit the fundamental absorption band in the UV light region, while the absorption edge shifts towards visible light region obviously for the W-doped TiO₂ materials. Furthermore, a gradual red shift of absorption edge is noticed along with increasing the amount of W, when the amount of W is smaller than 0.8%. The absorption of the UV light in TiO₂ is ascribed to the excitation of the O2p electron to the Ti3d level [41]. The red-shifted absorption edge for W-doped TiO₂ may be associated with the charge transfer between TiO₂ valence or conduction band and W ion level. It implies that the bandgap of TiO₂ can be adjusted by the trapping level, which is formed through doping with appropriate metal ions. It has been reported that the existence of La can also result in the red shift of absorption range of TiO₂ to visible light region [42]. As shown in Figure 5(a), it is also found that the absorption edge of 4% La/W/TiO₂ is red-shifted compared with that of 0.8% W/TiO₂. The bandgaps estimated from the plots of ()² versus photon energy are presented in Figure 5(b) and it is apparent W-doping and La-doping lead to the decrease of bandgap of TiO₂ from 3.19 to 3.10 eV, indicating that the obtained TiO₂ nanomaterials display the visible light response. They are anticipated to exhibit better photochemical activity under visible light.

(a)

(b)

In order to further investigate the texture of the obtained composites, N₂ adsorption/desorption measurements are conducted. Figure 6(a) shows the nitrogen adsorption-desorption isotherms of pure TiO₂, W-doped TiO₂, and W-La-codoped TiO₂ nanomaterials. The isotherms are characteristic of type-IV curves, indicating the presence of mesoporosity in the synthesized materials. Figure 6(b) shows the pore size distributions of pure TiO₂, W-doped TiO₂, and W-La-codoped TiO₂. It is clearly seen that the pores in pure TiO₂ have the diameter of about 4 nm, whereas the majority of pores in W-doped TiO₂ and W-La-codoped TiO₂ are around 2 nm. However, it should be noted that some mesopores with the diameter of 5 nm are present in W-doped TiO₂. The BET specific surface areas of pure TiO₂, W-doped TiO₂, and W-La-codoped TiO₂ are 5.0, 86.3, and 102.7 . The higher specific surface areas of W-doped TiO₂ and W-La-codoped TiO₂ are ascribed to the smaller particle size. For comparison, P25 is also characterized by N₂ adsorption/desorption measurement. The BET specific surface area is 42.8 and the main diameter of pores is approximately 2 nm.

(a)

(b)

The photocatalytic activity of the W-doped TiO₂ nanocrystals is evaluated by photodecolorization of MO solution, which is a typical azo dye and difficult to be degraded. Figure 7(a) presents the adsorption effect of pure TiO₂, 0.8% W/TiO₂, and 4% La/W/TiO₂ on MO in the dark. The adsorption equilibrium is reached for all three samples after 20 min. It is obvious that the adsorption capacity of 4% La/W/TiO₂ is superior to those of pure TiO₂ and 0.8% W/TiO₂, due to the large specific surface area of 4% La/W/TiO₂. Figure 7(b) presents the photocatalytic performance for the decolorization efficiency of MO solution in the presence of P25, pure TiO₂, and W-doped TiO₂ nanocrystals. It is clear that all of the W-doped TiO₂ nanomaterials exhibit higher photocatalytic activity than that of pure TiO₂ and P25, which possess the similar porous structures. This is attributed to improved photoinduced charge carriers separation, enhanced light absorption, and large surface area. Under simulated sunlight irradiation, the electrons in the TiO₂ structures can be easily excited from the valence band into the conduction band. Then the excited electrons in the conduction band probably transfer to the W ion states and the holes are left in the valence band [35]. Subsequently, the charge carriers transfer to the surface of photocatalyst and initiate the oxidation of MO. In addition, W-doping increases the light absorption owing to the red shift of absorption range to the visible light region. Meanwhile, the surface area is also important for photocatalytic activity. Comparing with the pure TiO₂ and P25, 0.8% W/TiO₂ nanomaterials display a larger surface area, giving birth to more contact area during photocatalystic reaction. All of above advantages make 0.8% W/TiO₂ nanomaterials present higher photocatalytic activity. It should be noted that the decolorization efficiency increases with increasing of the amount of W as long as it is smaller than 0.8%. Further increasing the dopant content results in the decrease of decolorization efficiency. It may be attributed to that W ions begin to act as recombination centers for the photogenerated electrons and holes, when the amount of W is larger than 0.8%. So the decolorization efficiency is dramatically decreased. Figure 7(c) displays the decolorization efficiency of MO over the as-synthesized products under simulated sunlight irradiation. It is obvious that the decolorization efficiency increases to 67.4% along with the increase of La-doping amount to 4%. Similar to W-doped TiO₂, further increasing the amount of La results in the decrease of decolorization efficiency. And all of the W-La-codoped TiO₂ nanomaterials exhibit higher photocatalytic activity than those of W-doped TiO₂ nanomaterials. According to previous report [31], La₂O₃ on the surface of TiO₂ may favor the separation of charge carriers and prolong the life of carriers. In addition, the existence of La₂O₃ can also increase the amount of hydroxyl radicals on the surface of the photocatalyst, available for oxidation of MO. As a result, the presence of La enhances the photocatalytic activity of W-La-codoped TiO₂ nanomaterials. The efficient charge separation in the W-doped TiO₂ and W-La-codoped nanomaterials is confirmed by PL spectra. As observed in Figure 7(d), 0.8% W/TiO₂ exhibits much lower emission intensity than that of pure TiO₂ nanomaterials, indicating that the recombination of the photoinduced charge carrier is greatly inhibited in 0.8% W/TiO₂ nanomaterials. It can also be found that W-La-codoped TiO₂ presents apparent quenching of the W-doped TiO₂ fluorescence, which indicates the suppression of the recombination of electrons and holes.

(a)

(b)

(c)

(d)

Figure 7

(a) Decolorization profiles of MO in the presence of (A) pure TiO₂, (B) 0.8% W/TiO₂, and (C) 4% La/W/TiO₂ in the dark. Photocatalytic decolorization curves of MO over the catalysts under simulated sunlight irradiation: (A) blank, (B) P25, (C) pure TiO₂, (D) 0.4% W/TiO₂, (E) 0.6% W/TiO₂, (F) 0.8% W/TiO₂, (G) 1.0% W/TiO₂, and (H) 1.2% W/TiO₂ in (b) and (A) 0.8% W/TiO₂, (B) 1% La/W/TiO₂, (C) 2% La/W/TiO₂, (D) 3% La/W/TiO₂, (E) 4% La/W/TiO₂, and (F) 5% La/W/TiO₂ in (c). (d) PL spectra of the (A) pure TiO₂, (B) 0.8% W/TiO₂, and (C) 4% La/W/TiO₂ nanomaterials.

The recycling performance is known as one of the main methods for describing the role of catalysts in practical applications. Figure 8 shows the recycling behaviors of 0.8% W/TiO₂ and 4% La/W/TiO₂ for decolorization of MO. It is seen that the decolorization efficiency of MO using 0.8% W/TiO₂ and 4% La/W/TiO₂ reaches 45.0% and 67.4% in the first cycle. After five cycles, the decolorization efficiency of MO on 0.8% W/TiO₂ and 4% La/W/TiO₂ is 42.8 and 65.1%, respectively, indicating both 0.8% W/TiO₂ and 4% La/W/TiO₂ possess superior recycling ability.

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(b)

In order to get a better comparison of the photocatalytic activities of the doped TiO₂ nanomaterials, the kinetic analysis of decolorization of MO is also discussed. As shown in Figure 9, the kinetic linear simulation curves of the photocatalytic decolorization of MO solution in the presence of different photocatalysts show that all the decolorization reactions can be described by first-order reaction dynamics due to the low initial concentration of the MO solution (20 in this case). Meanwhile, the slopes of these lines suggest the reaction rate constant of 4% La/W/TiO₂ is larger than any other sample in this case, implying 4% La/W/TiO₂ nanomaterials possess the highest photocatalytic activity.

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(b)

4. Conclusions

In summary, the W-doped TiO₂ and W-La-codoped TiO₂ nanomaterials are prepared through a sol-gel method. The presence of W and La results in red shift of absorption edge for TiO₂ nanomaterials. The investigation of photocatalytic activity indicates the W-doped and La-doped can effectively improve the photocatalytic activity of TiO₂ under simulated sunlight irradiation due to improved photoinduced charge carriers separation, enhanced light absorption, and large surface area. Considering their high photocatalytic activity, the doped TiO₂ nanomaterials can be applied in wastewater treatment and environmental purification.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgments

The research was supported by Program for Key Science & Technology Platform (191) in Universities of Liaoning Province, the National Natural Science Foundation of China (Grant no. 21476033), and Cultivation Program for Excellent Talents of Science and Technology Department of Liaoning Province (no. 201402610).

References

J. Hoigne and H. Bader, “The role of hydroxyl radical reactions in ozonation processes in aqueous solutions,” Water Research, vol. 10, no. 5, pp. 377–386, 1976.
View at: Publisher Site | Google Scholar
S. Rasalingam, R. Peng, and R. T. Koodali, “Removal of hazardous pollutants from wastewaters: applications of TiO₂-SiO₂ mixed oxide materials,” Journal of Nanomaterials, vol. 2014, Article ID 617405, 42 pages, 2014.
View at: Publisher Site | Google Scholar
J. Li, L. Gao, Q. Zhang et al., “Photocatalytic property of Fe₃O₄/SiO₂/TiO₂ core-shell nanoparticle with different functional layer thicknesses,” Journal of Nanomaterials, vol. 2014, Article ID 986809, 7 pages, 2014.
View at: Publisher Site | Google Scholar
Q.-P. Luo, X.-Y. Yu, B.-X. Lei, H.-Y. Chen, D.-B. Kuang, and C.-Y. Su, “Reduced graphene oxide-hierarchical ZnO hollow sphere composites with enhanced photocurrent and photocatalytic activity,” The Journal of Physical Chemistry C, vol. 116, no. 14, pp. 8111–8117, 2012.
View at: Publisher Site | Google Scholar
L. Andronic, D. Andrasi, A. Enesca, M. Visa, and A. Duta, “The influence of titanium dioxide phase composition on dyes photocatalysis,” Journal of Sol-Gel Science and Technology, vol. 58, no. 1, pp. 201–208, 2011.
View at: Publisher Site | Google Scholar
Y. A. Cao, W. S. Yang, W. F. Zhang, G. Z. Liu, and P. Yue, “Improved photocatalytic activity of Sn⁴⁺ doped TiO₂ nanoparticulate films prepared by plasma-enhanced chemical vapor deposition,” New Journal of Chemistry, vol. 28, no. 2, pp. 218–222, 2004.
View at: Publisher Site | Google Scholar
A. Bumajdad, M. Madkour, Y. Abdel-Moneam, and M. El-Kemary, “Nanostructured mesoporous Au/TiO₂ for photocatalytic degradation of a textile dye: the effect of size similarity of the deposited Au with that of TiO₂ pores,” Journal of Materials Science, vol. 49, no. 4, pp. 1743–1754, 2014.
View at: Publisher Site | Google Scholar
H. Zhang, X. Lv, Y. Li, Y. Wang, and J. Li, “P25-graphene composite as a high performance photocatalyst,” ACS Nano, vol. 4, no. 1, pp. 380–386, 2010.
View at: Publisher Site | Google Scholar
T. López, M. Alvarez, F. Tzompantzi, and M. Picquart, “Photocatalytic degradation of 2,4-dichlorophenoxiacetic acid and 2,4,6-trichlorophenol with ZrO₂ and Mn/ZrO₂ sol-gel materials,” Journal of Sol-Gel Science and Technology, vol. 37, no. 3, pp. 207–211, 2006.
View at: Publisher Site | Google Scholar
J.-M. Herrmann, C. Duchamp, M. Karkmaz et al., “Environmental green chemistry as defined by photocatalysis,” Journal of Hazardous Materials, vol. 146, no. 3, pp. 624–629, 2007.
View at: Publisher Site | Google Scholar
Y. Tang, Z. Jiang, G. Xing et al., “Efficient Ag@AgCl cubic cage photocatalysts profit from ultrafast plasmon-induced electron transfer processes,” Advanced Functional Materials, vol. 23, no. 23, pp. 2932–2940, 2013.
View at: Publisher Site | Google Scholar
Z. Zhang, C. Shao, X. Li et al., “Hierarchical assembly of ultrathin hexagonal SnS₂ nanosheets onto electrospun TiO₂ nanofibers: enhanced photocatalytic activity based on photoinduced interfacial charge transfer,” Nanoscale, vol. 5, no. 2, pp. 606–618, 2013.
View at: Publisher Site | Google Scholar
D. Li, W. Wu, Y. Zhang, L. Liu, and C. Pan, “Preparation of ZnO/graphene heterojunction via high temperature and its photocatalytic property,” Journal of Materials Science, vol. 49, no. 4, pp. 1854–1860, 2014.
View at: Publisher Site | Google Scholar
M. M. Uddin, M. A. Hasnat, A. J. F. Samed, and R. K. Majumdar, “Influence of TiO₂ and ZnO photocatalysts on adsorption and degradation behaviour of Erythrosine,” Dyes and Pigments, vol. 75, no. 1, pp. 207–212, 2007.
View at: Publisher Site | Google Scholar
H. E. Byrne and D. W. Mazyck, “Removal of trace level aqueous mercury by adsorption and photocatalysis on silica-titania composites,” Journal of Hazardous Materials, vol. 170, no. 2-3, pp. 915–919, 2009.
View at: Publisher Site | Google Scholar
A. Ye, W. Fan, Q. Zhang, W. Deng, and Y. Wang, “CdS-graphene and CdS-CNT nanocomposites as visible-light photocatalysts for hydrogen evolution and organic dye degradation,” Catalysis Science & Technology, vol. 2, no. 5, pp. 969–978, 2012.
View at: Publisher Site | Google Scholar
M. Huang, C. Xu, Z. Wu, Y. Huang, J. Lin, and J. Wu, “Photocatalytic discolorization of methyl orange solution by Pt modified TiO₂ loaded on natural zeolite,” Dyes and Pigments, vol. 77, no. 2, pp. 327–334, 2008.
View at: Publisher Site | Google Scholar
A. Zakersalehi, M. Nadagouda, and H. Choi, “Suppressing NOM access to controlled porous TiO₂ particles enhances the decomposition of target water contaminants,” Catalysis Communications, vol. 41, pp. 79–82, 2013.
View at: Publisher Site | Google Scholar
X. Pan, M.-Q. Yang, X. Fu, N. Zhang, and Y.-J. Xu, “Defective TiO₂ with oxygen vacancies: synthesis, properties and photocatalytic applications,” Nanoscale, vol. 5, no. 9, pp. 3601–3614, 2013.
View at: Publisher Site | Google Scholar
Z. Jiang, Y. Tang, Q. Tay et al., “Understanding the role of nanostructures for efficient hydrogen generation on immobilized photocatalysts,” Advanced Energy Materials, vol. 3, no. 10, pp. 1368–1380, 2013.
View at: Publisher Site | Google Scholar
Y. Tang, P. Wee, Y. Lai et al., “Hierarchical TiO₂ nanoflakes and nanoparticles hybrid structure for improved photocatalytic activity,” Journal of Physical Chemistry C, vol. 116, no. 4, pp. 2772–2780, 2012.
View at: Publisher Site | Google Scholar
M. Antoniadou, V. M. Daskalaki, and N. Balis, “Photocatalysis and photoelectrocatalysis using (CdS-ZnS)/TiO₂ combined photocatalysts,” Applied Catalysis B: Environmental, vol. 107, pp. 188–196, 2011.
View at: Publisher Site | Google Scholar
B. Tryba, M. Piszcz, and A. W. Morawski, “Photocatalytic activity of TiO₂ - WO₃ composites,” International Journal of Photoenergy, vol. 2009, Article ID 297319, 7 pages, 2009.
View at: Publisher Site | Google Scholar
Y. Peng, C. X. Liu, X. Y. Zhang, and J. H. Li, “The effect of SiO₂ on a novel CeO₂-WO₃/TiO₂ catalyst for the selective catalytic reduction of NO with NH₃,” Applied Catalysis B: Environmental, vol. 140, pp. 276–282, 2013.
View at: Publisher Site | Google Scholar
M. Grätzel and R. F. Howe, “Electron paramagnetic resonance studies of doped titanium dioxide colloids,” The Journal of Physical Chemistry, vol. 94, no. 6, pp. 2566–2572, 1990.
View at: Publisher Site | Google Scholar
A. Di Paola, G. Marcì, L. Palmisano et al., “Preparation of polycrystalline TiO₂ photocatalysts impregnated with various transition metal ions: characterization and photocatalytic activity for the degradation of 4-nitrophenol,” The Journal of Physical Chemistry B, vol. 106, no. 3, pp. 637–645, 2002.
View at: Publisher Site | Google Scholar
Y.-K. Lai, J.-Y. Huang, H.-F. Zhang et al., “Nitrogen-doped TiO₂ nanotube array films with enhanced photocatalytic activity under various light sources,” Journal of Hazardous Materials, vol. 184, no. 1–3, pp. 855–863, 2010.
View at: Publisher Site | Google Scholar
D. Wang, Z.-H. Zhou, H. Yang, K.-B. Shen, Y. Huang, and S. Shen, “Preparation of TiO₂ loaded with crystalline nano Ag by a one-step low-temperature hydrothermal method,” Journal of Materials Chemistry, vol. 22, no. 32, pp. 16306–16311, 2012.
View at: Publisher Site | Google Scholar
N. Wang, T. Tachikawa, and T. Majima, “Single-molecule, single-particle observation of size-dependent photocatalytic activity in Au/TiO₂ nanocomposites,” Chemical Science, vol. 2, no. 5, pp. 891–900, 2011.
View at: Publisher Site | Google Scholar
Z.-L. Ma, G.-F. Huang, D.-S. Xu, M.-G. Xia, W.-Q. Huang, and Y. Tian, “Coupling effect of la doping and porphyrin sensitization on photocatalytic activity of nanocrystalline TiO₂,” Materials Letters, vol. 108, pp. 37–40, 2013.
View at: Publisher Site | Google Scholar
A.-W. Xu, Y. Gao, and H.-Q. Liu, “The preparation, characterization, and their photocatalytic activities of rare-earth-doped TiO₂ nanoparticles,” Journal of Catalysis, vol. 207, no. 2, pp. 151–157, 2002.
View at: Publisher Site | Google Scholar
R. Gopalan and Y. S. Lin, “Evolution of pore and phase structure of sol-gel derived lanthana doped titania at high temperatures,” Industrial and Engineering Chemistry Research, vol. 34, no. 4, pp. 1189–1195, 1995.
View at: Publisher Site | Google Scholar
H. Cai, X. Chen, Q. Li, B. He, and Q. Tang, “Enhanced photocatalytic activity from Gd, la codoped TiO₂ nanotube array photocatalysts under visible-light irradiation,” Applied Surface Science, vol. 284, pp. 837–842, 2013.
View at: Publisher Site | Google Scholar
Y. B. Xie and C. W. Yuan, “Rare earth ion modified TiO₂ sols for photocatalysis application under visible light excitation,” Rare Metals, vol. 23, no. 1, pp. 20–26, 2004.
View at: Google Scholar
W. Wu, X. Hu, T. Xie, G. Li, and L. Zhang, “Phase structure of W-doped nano-TiO₂ produced by sol-gel method,” China Particuology, vol. 3, no. 4, pp. 233–236, 2005.
View at: Publisher Site | Google Scholar
S. Yao, X. Jia, L. Jiao, C. Zhu, and Z. Shi, “La-doped TiO₂ hollow fibers and their photocatalytic activity under UV and visible light,” Indian Journal of Chemistry A, vol. 51, no. 8, pp. 1049–1056, 2012.
View at: Google Scholar
G. E. Mcguire, G. K. Schweitzer, and T. A. Carlson, “Study of core electron binding energies in some group IIIa, Vb, and VIb compounds,” Inorganic Chemistry, vol. 12, no. 10, pp. 2450–2453, 1973.
View at: Publisher Site | Google Scholar
Y. Wang, T. Chen, and Q. Mu, “Electrochemical performance of W-doped anatase TiO₂ nanoparticles as an electrode material for lithium-ion batteries,” Journal of Materials Chemistry, vol. 21, no. 16, pp. 6006–6013, 2011.
View at: Publisher Site | Google Scholar
L. J. Xiang and T. Nathan-Walleser, “Hydrothermal synthesis of W-doped titania nanofibers and its photocatalytic activity,” International Journal of Material Science, vol. 3, pp. 104–109, 2013.
View at: Google Scholar
V. Štengl, S. Bakardjieva, and N. Murafa, “Preparation and photocatalytic activity of rare earth doped TiO₂ nanoparticles,” Materials Chemistry and Physics, vol. 114, no. 1, pp. 217–226, 2009.
View at: Publisher Site | Google Scholar
K. S. Kim and N. Winograd, “Charge transfer shake-up satellites in X-ray photoelectron spectra of cations and anions of SrTiO₃, TiO₂ and Sc₂O₃,” Chemical Physics Letters, vol. 31, no. 2, pp. 312–317, 1975.
View at: Publisher Site | Google Scholar
C. Wen, H. Deng, J.-Y. Tian, and J.-M. Zhang, “Photocatalytic activity enhancing for TiO₂ photocatalyst by doping with La,” Transactions of Nonferrous Metals Society of China, vol. 16, pp. s728–s731, 2006.
View at: Publisher Site | Google Scholar

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Copyright © 2014 Chenghe Hua et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Journal of Nanomaterials

Enhanced Photocatalytic Activity of W-Doped and W-La-Codoped TiO2 Nanomaterials under Simulated Sunlight

Abstract

1. Introduction

2. Experimental Section

2.1. Materials

2.2. Preparation of W-Doped TiO2 Nanomaterials

2.3. Preparation of W-La-Codoped TiO2 Nanomaterials

2.4. Characterization

2.5. Photocatalytic Decolorization of MO Solution

3. Results and Discussion

4. Conclusions

Conflict of Interests

Acknowledgments

References

Copyright

Enhanced Photocatalytic Activity of W-Doped and W-La-Codoped TiO₂ Nanomaterials under Simulated Sunlight

2.2. Preparation of W-Doped TiO₂ Nanomaterials

2.3. Preparation of W-La-Codoped TiO₂ Nanomaterials