Elsevier

Catalysis Communications

Volume 36, 5 June 2013, Pages 89-93
Catalysis Communications

Short Communication
Novel one-step preparation of tungsten loaded TiO2 nanotube arrays with enhanced photoelectrocatalytic activity for pollutant degradation and hydrogen production

https://doi.org/10.1016/j.catcom.2013.03.009Get rights and content

Highlights

  • W-TiO2NTs were prepared via an electrochemical oxidation method.

  • Tungsten was successfully incorporated into TiO2 lattice in a form of W6 + ion.

  • W-TiO2NTs showed high PEC activity to remove RhB and production of hydrogen.

  • Optimum W content acts as an electron acceptor.

Abstract

Highly ordered tungsten doped TiO2 nanotube arrays (W-TiO2NTs) were prepared in glycerol/fluoride electrolyte solution containing sodium tungstate via the electrochemical oxidation of a Ti substrate. The resulting arrays were characterized by XRD, SEM, and XPS. The 15 mM W-TiO2NTs exhibited better photoelectrochemical activity than the TiO2NTs and W-TiO2NTs fabricated using other W concentrations under Xe illumination. The W ion was successfully introduced into the TiO2 crystal lattice in the W6 + form according to the XPS analysis, which enhanced the photoelectrocatalytic activity of the W-TiO2NTs, as indicated by the efficient removal of Rhodamine B and the production of hydrogen.

Introduction

TiO2 nanotube arrays (TiO2NTs) are subject to extensive research in photocatalysis and photoelectrocatalysis because of their special properties, including a large surface area, high regulation, prominent controllability, and superior electron transport rate [1]. Anodization represents one of the most promising approaches among all the methods for TiO2NT synthesis [2]. The different types of electrolytes and the desired anodization time can be used to fabricate NTs with adjustable shapes and sizes. However, given its high band gap, TiO2 is a UV-driven photocatalyst [3], [4], which severely limits the applicability of TiO2NTs under visible light.

The doping of NTs with either metal or non-metal elements [5], [6], [7], [8] is a proven effective method of synthesizing efficient photocatalysts in the visible light range. A great deal of research has been directed towards using tungsten (W) to modify TiO2 in the form of nanopowder [9], film [10], and core-shell [11] because the W ion is considered one of best elements for narrowing the band gap of TiO2 [12], [13]. Despite the variety of synthetic methods and products reported, these methods have certain shortcomings. Lewera [14] fixed TiO2 with WO3, but the catalyst was easily lost during photocatalysis. Lai [15] utilized the plasma electrolytic method to fabricate W-loaded TiO2 nanotubes; however, special equipment was required to achieve the spluttering coating. Other researchers [16] achieved W-doped TiO2 nanotubes using alloys but encountered difficulty in adjusting the dopant concentration. Therefore, a simple, facile, and inexpensive method of synthesizing W-doped TiO2NTs is necessary.

In the present study, we report a controllable approach to fabricating W-doped TiO2NTs through the electrochemical oxidation of a Ti substrate in glycerol/fluoride electrolyte containing sodium tungstate. The high efficiency of the photoelectrochemical (PEC) properties of W-doped TiO2 can be prepared by doping different sodium tungstate concentrations in the electrolyte. The PEC properties of W-doped TiO2 can also be controlled by annealing the electrode at various temperatures to obtain the anatase crystal phase. The high photocatalytic activities of W-doped TiO2 were evaluated through the PEC degradation of Rhodamine B (RhB) and hydrogen generation.

Section snippets

Reagents

Ti foil (0.5 mm thick, 99% purity) was purchased from Baoji Titanium Industry Co., Ltd, China. Sodium tungstate (Na2WO4 · 2H2O), HF, HNO3, Na2SO4, glycerol, ethanol and RhB were obtained from Sinopharm Chemical Reagent Co., Ltd, China. Na2S and Na2SO3 were purchased from Sigmal. All chemicals were of analytical grade without further purifying before experiment and solutions were prepared with deionized water.

Preparation of W-TiO2NTs

The highly ordered W-TiO2NTs were synthesized by anodic oxidation in a mixture

Results and discussion

The as-prepared W-TiO2NTs exhibited regular arrays with a uniform size distribution of around 35 nm, as shown in Fig. 1A. The inset of Fig. 1A presents the nanotube profile at ~ 850 nm. The morphology of the W-TiO2NTs is similar to those reported in previous studies [18], [19], indicating that the W-doping process does not influence the morphologies of the TiO2NT samples. Fig. 1B shows the XRD patterns of W-TiO2NTs doped with different concentrations annealed at 400 °C. The W-TiO2NTs consist of a

Conclusion

In summary, we successfully prepared highly ordered W-TiO2NTs with an exclusive anatase phase utilizing a facile and novel anodization process on a Ti sheet. The morphology, crystal phase, chemical composition, and photoelectrocatalytic activity of the prepared samples were evaluated using various characterization techniques. XPS analysis showed that W atoms were successfully incorporated into the TiO2 lattice in the form of W6 + ions, which resulted in the high photoelectrocatalytic activity of

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 20977037). The authors thank the Analytical and Testing Center of HUST for the use of SEM and XRD equipment.

References (27)

  • G. Mor et al.

    Solar Energy Materials and Solar Cells

    (2006)
  • K. Nakata et al.

    Photobiology C

    (2012)
  • V.D. Binas et al.

    Applied Catalysis B: Environmental

    (2012)
  • M. Li et al.

    Catalysis Communications

    (2012)
  • D.S. Zhang et al.

    Catalysis Communications

    (2012)
  • P. Kompio et al.

    Journal of Catalysis

    (2012)
  • W.L. Kwong et al.

    Electrochimica Acta

    (2012)
  • W. Smith et al.

    Catalysis Communications

    (2009)
  • C.W. Lai et al.

    Electrochimica Acta

    (2012)
  • C. Das et al.

    Electrochimica Acta

    (2011)
  • J.Y. Gong et al.

    Chemical Engineering Journal

    (2012)
  • S. Bauer et al.

    Electrochemistry Communications

    (2011)
  • M.X. Sun et al.

    Electrochemistry Communications

    (2012)
  • Cited by (0)

    View full text