No abstract

Surface-modified ZnO photocatalysts with enhanced UVA-light-driven and visible-light-driven activities were synthesized by the thermal shock method with Cu(NO 3 ) 2 at different thermal shock temperatures (300 -600°C). The influences of thermal shock temperatures on the crystal structure, morphology, surface functional groups and surface composition of modified catalysts were investigated by XRD, TEM, Raman and XPS spectra, respectively. Their photocatalytic activity was evaluated via the degradation of methylene blue under both UVA and visible light irradiation. According to the results, by combining the thermal shock method and an agent with low thermal stability such as Cu(NO 3 ) 2 , we did not modify the crystal structure, phase composition nor the morphology of ZnO nanoparticles, but successfully modified the surface of ZnO nanoparticles with the migration of zinc ions, leading to the creation of new environments of Zn 2+ and O 2ions as well as the formation of surface zinc vacancies. These evolutions were found to be able to enhance the photocatalytic performance in the UVA light region and also in the visible light region.

The Cu doped ZnO photocatalysts were prepared on ZnO substrate modified with copper nitrate by thermal shock method with different ratio % molar Cu : Zn = 0.3, 0.5, 1.0, 2.0 and 5.0 in order to study the impacts of copper content on the photocatalytic activity of ZnO under both UV and Vis light irradiation. The crystal structure, morphology bulk and surface were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Their photocatalytic activities were studied via time-dependent degradation of methylene blue in aqueous solution. The results exhibit that crystal structure and morphology of Cu doped ZnO photocatalysts is not modified significally than ZnO original but surface charateristicschanged greatly. The photocatalyst was doped with copper content under 2% showed formation of Cu species. These samples perform photocatalytic activity higher than ZnO. The CuNZO-0.05-500 had the highest rate constants for methylene blue degradation (kUV = 6,901 h-1, kVIS = 0,224 h-1), which are about 2.2 times and 1.3 times higher than unmodified ZnO under UV light and Vis light, respectively. However, the CuNZO-5.0-500 which had the formation of CuO phase and unchangeable ZnO's surface has photocatalytic activity similar to pure ZnO.