Heterojunction Composites WO3/MoS2-Rgo with Enhanced Photocatalytic Degradation Efficiency Under Visible Light Irradiation
Authors: Li Gang , Hou Jingjing , Zhao Qinghua , Hu Jie , Wang Yingge , Chen Xuyuan , Wang Kaiying 
Published: February 2020

Semiconductor photochemical treatment is expected to be a green technology for solving the environmental issues induced by organic pollutants. WO3 are generally considered as an excellent candidate for visible-light photocatalysts [1-3]. However, the activity of pure WO3 has to be improved due to the rapid recombination of the photogenerated electron-hole pairs. In this work, WO3 was loaded with hybrid MoS2-reduced graphene oxide (MoS2-rGO) to form WO3/MoS2-rGOheterojunction composites, in which MoS2 acts as another efficient light absorbing material and rGO as the charge transfer medium to enhance the photocatalytic efficiency [4-5].
In this work, WO3 was prepared by hydrothermal synthesis method with WCl6 as tungsten source and absolute ethanol as solvent, as shown in Fig. 1(a). Clearly, the synthesized WO3 is a monodispersed microsphere structure with an average size of 2-3um. The hybrid MoS2-rGO was prepared by adding graphene during the hydrothermal synthesis process of MoS2 with Na2MoO4·2H2O and thiourea as reacting materials. As shown in Fig. 1(b), the synthesized MoS2 shows a flower-like structure. Finally, the WO3/MoS2-rGO nanocomposites were also prepared by adding the prepared hybrid MoS2-rGO during the hydrothermal synthesis process of WO3. As shown in Fig. 1(c) and (d), the close contact is clearly seen between the microsphere-like WO3 and flower-like hybrid MoS2-rGO, and the second hydrothermal process had no influence on the structure of WO3 and hybrid MoS2-rGO. X-ray diffraction (XRD) patterns and Raman spectra are respectively measured to determine the crystal structure, as shown in Fig.1 (e) and (f).
The photochemical behaviors of WO3/MoS2-rGO nanocomposites containing (0, 2%, 5%, 10%, and 20%) of hybrid MoS2-rGO are characterized through the degradation behaviors of rhodamine (RhB) under visible light irradiation (Fig.2). The experimental results clearly show that the degradation efficiency of WO3/MoS2-rGO nanocomposites can be improved by optimizing the mass ratio of WO3 microspheres to hybrid MoS2-rGO flowers. The degradation ratios of RhB after 6 h are 78.2%, 79.5%, 82.6%, 95.6%, 91.8%, correspond respectively to the WO3/MoS2-rGO nanocomposites containing 0, 2%, 5%, 10%, and 20% of hybrid MoS2-rGO. The possible reason is that the formed WO3/MoS2heterojunction structure and charge transfer medium of rGO is beneficial for separating electron-hole pairs for high efficiency degradation
In summary, the WO3 microspheres and different WO3/MoS2-rGO nanocomposites have been prepared and characterized through adjusting the mass ratio of WO3 microspheres to hybrid MoS2-rGO flowers. The results show that the optimized degradation ratio of RhB can be greatly improved from 78.2% up to 95.6% after 6h using WO3/MoS2-rGO nanocomposites in comparison with WO3 microspheres.

References

[1] J. Georgieva, E. Valova, S. Armyanov, N. Philippidis, I. Poulios, S. Sotiropoulos, Journal of Hazardous Materials 211–212 (2012) 30–46.
[2] S.Y. Yao, X. Zhang, F.Y. Qu, A. Umar, X. Wu, Journal of Alloys and Compounds 689 (2016) 570–574.
[3] S.V. Mohite, V.V. Ganbavle, K.Y. Rajpure, Journal of Alloys and Compounds 655 (2016) 106–113.
[4] B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, A. Kis, Nature Nanotechnology, 6 (2011) 147–150.
[5] P. Devi, C. Sharma, P. Kumar, M. Kumar, B. K.S. Bansod, M. K. Nayak, M. L. Singla, Journal of Hazardous Materials, 322 (2017) 85–94.

Figure 1