Preparation And Photocatalytic Activity Of Doping Nano Zinc-Germanate Photocatalyst

Semiconductor photocatalytic technology plays a very important role in environmental pollution control due to the ability of light-induced redox. It has become a promising technology of solar energy utilization. Therfore, developing and designing new type of efficient semiconductor photocatalyst is the key to environmental photocatalysis technology. Zn2GeO4, as a new type of bimetallic oxide semiconductor material, has become a photocatalytic material with a broad range of research value due to its good stability and more dispersed energy level structure. These special properties make the photo-generated electrons have high mobility in the conduction-band(CB) of Zn2GeO4, thus owning excellent optical transmission performance. However, Zn2GeO4can utilize no more than5%of the total solar energy impinging on the surface of the earth due to its wide bandgap (Eg=4.68eV). The modification of Zn2GeO4is necessary in order to extend the absorption wavelength and improve the utilization efficiency of light.It is well known that the combination of nonmetallic elements and photocatalysts could narrow the band gap and extend the scope of absorption wavelength and eventually improve the photocatalytic efficiency. In this study, RGO-Zn2GeO4, N-Zn2GeO4and (N,S)-Zn2GeO4composites were synthesized and their photocatalytic activities for the degradation of organic contaminant were investigated. The main contents of this study are as follows,(i) Zn2GeO4nanrods were synthesized by microwave hydrothermal reaction in an ethanol/water solvent system employing germanium oxide and zinc acetate as the raw material, and then doped with reduced graphene oxide (RGO). The effects of different mass ratio of RGO and methods on the photocatalytic activities of RGO-Zn2GeO4composites were investigated. The results suggested that the morphology and crystal structure of Zn2GeO4didn’t change when RGO was attached to Zn2GeO4. The composites prepared by two steps microwave hydrothermal process is the most efficient photocatalyst for the degradation of MO compared to the composite synthesized by in situ method. The enhanced photocatalytic activities could be attributed to the narrower band gap, the stronger interaction between RGO and Zn2GeO4and the higher migration efficiency of photoinduced electrons, which may suppress the charge recombination effectively.(ii) Zn2GeO4nanrods were synthesized by microwave hydrothermal reaction, and then doped with N employing urea as the sources of nitrogen.(N,S)-Zn2GeO4composites were synthesized by the same way employing thiourea as the sources of sulphur. The effects of different molar ratio of urea/thiourea to Zn2Ge04and calcination temperature on the photocatalytic activities of N-Zn2GeO4and (N,S)-Zn2GeO4composites were investigated. The incorporation of N or (N,S) has a great influence on the morphology and crystal structure of Zn2GeO4. The absorption edges of N-Zn2GeO4and (N,S)-Zn2GeO4composites had a large red shift from267nm to380and425nm, respectively. It could induce a significant increase in visible light absorption and make the Zn2GeO4harvesting visible light more effectively and exhibiting effective photocatalytic activity in visible light.