Construction of ZnO/Keggin Polyoxometalate Nano-heterojunction Catalyst for Efficient Removal of Rhodamine B in Aqueous Solution

Rational design of nano-heterojunction catalyst is one of the ideal ways to solve dye pollution effectively. In this study, two nano-heterojunction catalysts ZnO/Ag4SiW12O40 (ZnO/AgSiW) and ZnO/Cs3PW12O40 (ZnO/CsPW), were synthesized by the simple dissolution and precipitation method. The samples were characterized by XRD, TEM, FT-IR, Raman, DRS, XPS and N-2 adsorption and desorption isotherms. The photocatalytic experiments show that the degradation rates of Rhodamine B (RhB) by ZnO/AgSiW and ZnO/CsPW within 60 min are 92.3 and 72.7%, respectively, which are 5.3 and 4.2 times higher than that by pure zinc oxide. The two catalysts still maintain excellent performance after repeated use for three times. Based on the free radical capture experiment, the active substances that play a major role in the photocatalytic process were determined. In addition, the electrochemical tests show that the construction of a nano-heterojunction system significantly increases the separation efficiency of photogenerated carriers in the heterojunction system. The possible photocatalytic degradation pathways and final products of ZnO/AgSiW and ZnO/CsPW heterojunction nanocomposite catalysts were analyzed by the liquid chromatography/mass spectrometry (LC/MS) technique. This paper provides a theoretical and experimental basis for treating organic dyes by ZnO/AgSiW and ZnO/CsPW nano-heterojunction catalysts.

Automated summary

Rational design of nano-heterojunction catalysts, such as ZnO/AgSiW and ZnO/CsPW, can effectively solve dye pollution. This study synthesized and characterized these two catalysts, and conducted photocatalytic experiments and electrochemical tests. The results showed that the degradation rates of Rhodamine B by these catalysts were significantly higher than that by pure zinc oxide, and they maintained excellent performance after repeated use. The active substances and photocatalytic degradation pathways were determined through free radical capture experiments and liquid chromatography/mass spectrometry analysis.