Controlled Preparation And Properties Of TiO₂ Nanotubes Without And With Au,C Deposition

As a new type of nano-material,Ti O₂ nanotubes have attracted more and more attention in recent years due to their large specific surface area,thermal stability,non toxicity,photocatalytic activity and low cost.However,the TiO₂ nanotubes can only absorb the UV light in the solar energy,which greatly limits their application in the field of photocatalysis.Therefore,it is significant to study the preparation and modification of TiO₂ nanotubes.In this paper,the anodic oxidation method was used to prepare Ti O₂ nanotubes in the ethylene glycol solution containing 0.3wt%NH4F+2vol% water +1.5mol/L lactic acid.The TiO₂ nanotubes with different morphologies were prepared by changing the experimental parameters.TiO₂ nanotubes were modified by C nanoparticles prepared by a new ethanol carbonization method and Au nanoparticles prepared by photoreduction.The XRD,SEM,EDS,UV-Vis and other methods were used to characterize the phase,morphology,elemental composition and optical absorption of nanotubes.Moreover,the photocatalytic performance of Ti O₂ nanotubes was characterized by measuring photocurrent and photocatalytic degradation of rhodamine B.The results are as follows:The length of the nanotubes is proportional to the oxidation time under the condition of constant voltage and temperature.The relationship between growth rate and voltage is y = 0.4719e0.0424 x,and the R2 value is 0.9987.Pore diameter increases with the increase of voltage,and the nanotubes obtained at 40 V have the highest photocurrent and photocatalytic degradation of rhodamine B.The degradation degree reachs 88.28%.The photocatalytic degradation and photocurrent capacity increase with the increase of the length of the nanotube and decrease when exceeds the critical point of 15.75 ?m.The C nanoparticles were prepared by a new type of ethanol carbonization method and then deposited onto the surface and inner part of the nanotubes.Absorption spectrum has a red shift and the absorption peak boundary extends to the visible region,which increases the utilization rate of solar light.The band gap is 2.8 eV.It is reduced by 0.4 e V as compared the TiO₂ nanobubes without deposition.The C nanoparticles have the best effect when the diameter is about 5 nm and the atomic content is 6.68% when the photocurrent is about 4 times as high as the unmodified one.The Au nanoparticles with a particle size of 30-40 nm were prepared by the photo reduction method.They were uniformly distributed on the surface and inner part of the nanotubes.The UV diffuse reflectance absorption spectrum is shifted and the absorption peak extends to 410 nm.The band gap is 2.83 e V and reduced by 0.37 eV as compared to the unmodified Ti O₂ nanotubes.Three-cycle deposition have the best effect when the content ratio of the Au atoms is 0.70%.The photocurrent is 1.5 times higher than that of the unmodified one,and the photocatalytic degradation efficiency of Rh B is increased by 16%.The overall macroscopic morphology are changed by employing the network substrate to prepare nanotubes.There is still a highly ordered array of nanotubes on the micro level.The TiO₂ crystal is changed from the anatase phase to the mixed and rutile phases with the increase of crystallization temperature.The increase of temperature leads to the fracture of the nanotubes and the collapse of the surface,and the surface morphology of the nanotubes has been completely destroyed at 750?.The nanotubes treated at 550? have excellent photocatalytic properties.The results show that the photocatalytic degradation ratio of the three reticular basement nanotubes is higher than that of the sheet substrate by 12.7%.