Preparation, characterization and photocatalytic activity of Dawson type phosphotungstate/graphene oxide composites

In this study, single lacunary Dawson type tungstophosphate (P2W17) was modified with γ-(2,3-epoxypropoxy)propyltrimethoxysilane (EPO) to prepare P2W17-EPO containing epoxy groups, and graphene oxide (GO) was modified with 3-aminopropyltrimethoxysilane to prepare GO-NH2 containing amino groups. Then, P2W17 was covalently bonded onto the surface of GO through the reaction of P2W17-EPO with GO-NH2 for the preparation of GO/P2W17 composite photocatalysts, and their compositions and structures were characterized by the Fourier transform infrared spectroscopy, thermogravimetric analysis, X-Ray diffraction spectroscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, electrochemical impedance spectroscopy and BET analysis. The photocatalytic activity of GO/P2W17 for methylene blue (MB) was also investigated. The results show that the covalent bonding of P2W17 to GO results in an increase in the specific surface area, a reduction in the charge transfer impedance, and an increase in the transfer of photoinduced electrons. GO/P2W17 can effectively degrade MB in water under UV light and its photocatalytic activity is significantly higher than that of EPO-P2W17, which can be attributed to the synergetic effects of adsorption and photocatalytic degradation. GO speeds up the separation of photoexcited electron hole pairs of P2W17 during photocatalytic process. Besides, GO/P2W17 also has good reusability and its reuse for 6 times results in only a slight decrease in the degradation rate of MB. It is concluded that the covalent bonding of P2W17 onto GO can improve the photocatalytic activity of P2W17.