Preparation,Modification And Photocatalytic Performance Of TiO₂ Nanotube Arrays

TiO₂ has become a kind of promising photocatalytic material because of some outstanding properties.TiO₂ nanotube arrays（TiO₂ NTs）with unique tubular structure show better photocatalytic performance than other forms of TiO₂.However,the application of TiO₂ NTs is limited by its low utilization rate of solar energy and high recombination rate.So the preparation of TiO₂ NTs with high performance has become a hot spot currently.This paper carried out the controllable synthesis of TiO₂ NTs via two-step anodization method based on one-step anodization method.Ag and Au nanoparticles were adopted for the modification of the as-prepared TiO₂ NTs.The photocatalytic activity of the TiO₂ NTs was evaluated by degradation of methyl orange.TiO₂ NTs were prepared by one-step anodization method.The influence of different preparation parameters on morphology of TiO₂ NTs was investigated.The optimal preparation conditions of TiO₂ NTs is:in of electrolyte 0.3wt%NH4F+ethylene glycol+2vol%H2O,at 20℃ of electrolyte temperature,at 50V,anodic time is 1h,the calcination temperature at 450℃.For the defects of the TiO₂ NTs were prepared by one-step anodization method,the TiO₂ NTs with regular structure were prepared by two-step anodic oxidation.And the structure parameters of the honeycombed TiO₂ NTs can be controled by changing the voltage of second-step anodization process.The photocatalytic performance of Ti02 NTs was measured by photocatalytic degradation of methyl orange.The photocatalytic activity of one-step and two-step TiO₂NTs was compared.Also the different photocatalytic conditions on photocatalytic activitiy of degradation methyl orange were investigated with details.The results showed that the 2-step TiO₂NTs showed much higher photocatalytic activity than the 1-step one.The honeycombed TiO₂ NTs showed excellent photocatalytic performance and efficient stability.The most suitable process conditions should be as follows:anodizing voltage is 50V,anodizing 1.5h,calcinated at 450℃ and pH value of methyl orange is 3,the initial concentration of methyl orange and quantity of catalyst also affect the photocatalytic activity.Ag and Au modified TiO₂ NTs were successfully doped into TiO₂ NTs by electro-deposition method,the photocatalytic degradation of methyl orange showed that the photocatalytic activity of TiO₂ NTs could be significantly improved by doping process.