Characterization of visible-light-driven BiVO4 photocatalysts synthesized via a surfactant-assisted hydrothermal method

https://doi.org/10.1016/j.saa.2009.02.028Get rights and content

Abstract

Phase-pure BiVO4 photocatalysts were synthesized via a surfactant-assisted hydrothermal method and were characterized with XRD, DRS, Raman, FTIR and SEM. The results indicated that the HTAB-assisted BiVO4 had a narrow band gap than the other three products (no-surfactant-assisted, PVA-assisted and PVP-assisted BiVO4). The addition of surfactant would greatly affect the crystal structure of BiVO4, which can lead to different photocatalytic activities between them. Their photocatalytic activities were evaluated by the decolorization of methyl orange in aqueous solution under visible light irradiation; and the HTAB-assisted BiVO4 product, with well-assembled flower-like morphology, had a much higher photocatalytic activity (the photodegradation rate was about 85% in 90 min) than the other three products.

Introduction

In recent years, with the extensive researches carried out in the field of decomposition of harmful organic and inorganic pollutants using photocatalytic semiconductors, many effective UV-light photocatalysts and their photocatalytic behaviors has been extensively studied due to its potential application especially in environmental remediation, though whose photosensitized spectrum occupies only a little of the whole solar energy [1], [2], [3]. While, the visible light (λ > 400 nm) accounting for about half of the whole solar energy is open to exploiture, therefore, the development of visible-light-driven photocatalysts has become one of the most challenging topics recently [4], [5], [6].

Bismuth vanadate (BiVO4) has long been recognized as an important semiconductor due to its unique properties such as ferroelasticity [7] and ionic conductivity [8]. It has been used for a wide range of applications including gas sensors, solid-state electrolytes, positive electrode materials for lithium rechargeable batteries, nontoxic yellow pigment for high-performance lead-free paints [9] and recently proved to be a good photocatalyst for water splitting and pollutant decomposing under visible light irradiation [10]. BiVO4, a layered structured compound, always exists in three phases: monoclinic scheelite, tetragonal zircon, and tetragonal scheelite [11]. Up to now, several methods have been reported for the preparation of BiVO4, such as solid-state reaction, sol–gel method, coprecipitation and metal organic decomposition, etc. However, some of these methods require high reaction temperature, complex operating procedure, the high price of raw materials and the particle size of products is generally rather big. On the other hand, hydrothermal synthesis is a soft-chemical process that can be used to prepare advanced materials [12]. The wide range of operating temperatures available in aqueous media is the most attractive aspect of the approach for preparation of many different types of materials. Moreover, the hydrothermal conditions, such as the concentrations of precursors, pH, synthesis temperature, and synthesis time, additive species, among others, are easily controlled.

In the present work, a series of BiVO4 photocatalysts were synthesized via a surfactant-assisted hydrothermal method. The effects of different surfactants on crystal structure, morphology and spectroscopic properties of BiVO4 products were discussed in details. As the efficient visible-light-driven photocatalyst, the factors affecting the photocatalytic activities for dyes degradation over different BiVO4 products are also explored.

Section snippets

Materials and process

Bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and ammonium metavanadate (NH4VO3) from Beijing Chemical Company were used as received without further purification. All the other chemicals used in the experiments were analytical grade reagents, and deionized water was used for solution preparation. In a typical preparation process, 0.02 mol Bi(NO3)3·5H2O and 0.02 mol NH4VO3 were dissolved in 20 mL of 65% (w/w) HNO3 and 20 mL 6 mol/L NaOH solutions separately, and each stirred for 2 h at room

Powder formation

Fig. 1 shows the XRD patterns of no-surfactant-assisted BiVO4 (BV-NO), HTAB-assisted BiVO4 (BV-HTAB), PVA-assisted BiVO4 (BV-PVA) and PVP-assisted BiVO4 (BV-PVP). The XRD patterns of all these samples present similar profiles and all the diffraction peaks can be well indexed as monoclinic BiVO4 (JCPDS card No. 14-0688, space group I2/a, unit-cell parameters a =5.195 Å, b = 11.701 Å, c = 5.092 Å, β = 90.38°, mineral name: clinobisvanite). No other impurities such as Bi2O3 or other organic compounds

Conclusion

A series of BiVO4 photocatalysts were synthesized via a surfactant-assisted hydrothermal method. The XRD, SEM, UV–vis, and Raman spectroscopic characterizations revealed that not only the microstructure, such as the morphology, surface texture, and grain shape, but also the local structures of the synthesized BiVO4 materials were significantly dependent on the surfactant. In the presence of different surfactants during the synthetic system, the d(1 2 1) space of the BV-HTAB sample is smaller than

Acknowledgements

We acknowledge the financial support from the Scientific Research Foundation of North China University of Technology (NCUT) and the Natural Science Foundation of Beijing.

References (20)

  • A. Mills et al.

    J. Photochem. Photobiol. A: Chem.

    (1997)
  • S. Kohtani et al.

    Catal. Commun.

    (2005)
  • L. Zhou et al.

    J. Mol. Catal. A: Chem.

    (2006)
  • K. Hirota et al.

    Mater. Res. Bull.

    (1992)
  • K. Shantha et al.

    Mater. Sci. Eng. B

    (1999)
  • S. Kohtani et al.

    Appl. Catal. B: Environ.

    (2003)
  • M. Yoshimura et al.

    Mater. Chem. Phys.

    (1999)
  • W. Ueda et al.

    J. Catal.

    (1986)
  • M. Gotic et al.

    J. Mol. Struct.

    (2005)
  • J. Liu et al.

    Mater. Sci. Eng. B

    (2003)
There are more references available in the full text version of this article.

Cited by (0)

View full text