Preparation And Performances Of Hierarchically Ordered Porous ZnO-Graphene Composite Films

Nano-ZnO is promising in the photocatalysis and solar cells field due to its special pho-toelectric properties. However, the lower quantum efficiency and solar energy utilization are why the ZnO photocatalytic activity is not high, which limits it efficient application. In addition, the separation and recovery of nano-ZnO consume plenty of energy and time in the photo-degradation of dyes, which needs to be solved as soon as possible. Therefore, ordered porous ZnO films and ZnO-graphene composite films were synthesized, for improving photocatalytic activity and recyclability, through a graphene modified method and using glass slide as a support to immobilize and retrieve the nan-ZnO particle in this paper.Nano-ZnO films were prepared by dip-coating process and glass slide was chosen as a support which avoid the loss of nano-ZnO particle. Their properties were characterized by Field Emission-Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Ultraviolet-Visible Absorption Spectroscopy (UV-vis). It is demonstrated that ZnO crystal is six-party wurtzite structure and its size is 13.7nm. The photoactivity of nano-ZnO films was tested by photo-degradation methyl orange (MO) and methylene blue (MB) in aqueous solution under 500W mercury lamp light. It is shows that the degradation rate of methylene blue is higher than the degradation rate of methyl orange. With the increase of the concentration of methyl orange solution, the degradation rate of methyl orange first increases and then decrease and the deg-radation rate is fastest in 3mg/L solution. The degradation rate of recycled nano-ZnO films to methyl orange is over 70% and photocatalytic activity is good in this field.Ordered porous ZnO films were prepared by dip-coating method in which polystyrene spheres were acting as a scaffold structure on glass substrates. The optical properties and photocatalytic activity were investigated. Compared with nano-ZnO thin films, the light ab-sorption of ordered porous ZnO films was enhanced and the degradation rate of methyl orange increased from 80.2% to 94.7% within 90 min under 500W mercury lamp light. Because the porous structure enhance the utilization of light energy in the internal surface of ZnO. Addi-tionally, hierarchically ordered porous channels may facilitate diffusion of reactant molecules and enhance the reaction rate.To further improve the photocatalytic activity, nano-ZnO films were modified by gra-phene to prepare ordered porous ZnO-graphene composite films. Their properties were char-acterized by SEM, XRD. The optical properties, photocatalytic activity and recyclability were investigated. The results indicate that the introduction of graphene strengthen light absorption intensity of ZnO and its absorption wavelength range expanded to the visible light region. Its six-party wurtzite structure wasn’t changed. About degradation rate of methyl orange within 90 min under 500W mercury lamp light, the porous ZnO-graphene composite film is the highest (99.7%); the ZnO-graphene composite film is second place (93.5%); nano-ZnO thin film is the lowest (80.2%). Besides, the degradation rate of recycled ZnO-graphene composite films to methyl orange is higher than nano-ZnO films and photocatalytic activity is better.