Preparation and Photocatalytic Properties of g-C3N4/TiO2/BiVO4

Preparation and Photocatalytic Properties

of g-C₃N₄/TiO₂/BiVO₄

Shen Xinlin, Wang Youliang, Li Kebin, Wang Fengyun

The Institute of Industrial Chemistry, Nanjing University of Science & Technology, Nanjing 210094, P.R.China

Keyword: g-C₃N₄/TiO₂/BiVO₄; preparation; MB degradation

Over the last few decades, the semiconductor-based photocatalysis has emerged as an environmentally benign technology for wastewater treatment due to its destructive ability towards a wide range of inorganic and organic pollutants^[1-3] . TiO₂ is by far the most commonly being researched photocatalytic material owing to its many advantages for photocatalytic applications, e.g. high redox potentials, long-term thermodynamic stability, cost-effective and non-toxicity^[1,4,5]. Whereas the bare TiO₂ suffers from several disadvantages including the limit to ultraviolet (UV) light absorption due to its wide band gap, as well as low quantum efficiency resulting from the rapid recombination of photogenerated electron¨Chole pairs. To overcome these drawbacks and enhance the photocatalytic activity of TiO₂, we constructed and prepared a ternary catalyst, i.e., mpg-C₃N₄/TiO₂/BiVO₄.

The mpg-C₃N₄ was obtained in a typical synthesis: dicyandiamide was used as raw material and SBA-15 as template agent and calcined under nitrogen atmospheres. The binary and ternary catalysts were prepared by hydrothermal.

The XRD patterns of catalysts are shown in Figure 1. There are two peaks found in mpg-C₃N₄ sample at 12.28¡ãand 27.51¡ã, which can be indexed to (100) and (002) peak. The peaks at 25.5¡ã (101), 38.2¡ã (004), 48.2¡ã (200) and 54.9¡ã (105) indicate the existence of anatase TiO₂ phase (JCPDS No. 21-1272). The other diffraction peaks are agreement with monoclinic BiVO₄ phase (JCPDS No. 14-0688). No characteristic diffraction peaks of mpg-C₃N₄ can be observed for the ternary composite because of its low content and poor crystallization. But, its existence can be evidenced by FTIR spectra in figure 2. We have prepared the ternary mpg-C₃N₄/ BiVO₄/TiO₂ composite successfully.

Figure 1 : XRD patterns of mpg-C3N4; BiVO4; TiO2; BiVO4/TiO2; mpg-C3N4/ BiVO4/TiO2	Figure 2 : FTIR spectra of mpg-C3N4; BiVO4/TiO2;mpg-C3N4/ BiVO4/TiO2

The TEM images of catalysts are shown in figure 3, we can see the binary and ternary catalysts are the formation of heterojunction. Although the size of the structure reach micron grade, the minimum structure of the hierarchical structure unit is still the nanoscale.

The effect of photocatalytic degradation for methylene blue (MB) under visible light radiation (¦Ë ¡Ý 420 nm) is shown in figure 4. It shows that the methylene blue is almost completely degraded by the ternary mpg-C₃N₄/ BiVO₄/TiO₂ composite after 2 h. It proves that the mpg-C₃N₄/ BiVO₄/TiO₂ composite is more efficiently than the binary and pure catalysts.

Figure 3 : The TEM image of catalysts : (a) mpg-C3N4 ; (b) TiO2 ; (c) BiVO4 ; (d-e)BiVO4/TiO2 ; (f)mpg-C3N4/ BiVO4/TiO2	Figure 4 : The effect of photocatalytic degradation of methylene blue under visible radiation (¦Ë ¡Ý 420 nm)

The ternary mpg-C₃N₄/BiVO₄/TiO₂ catalysts have been prepared by calcination- hydrothermal successfully. It has been comfirmed of the formation of heterojunction by XRD, FTIR and TEM. The titled photocatalyst is efficiency for degradation of methylene blue under visible light radiation (¦Ë ¡Ý 420 nm).

References

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