The Preparation Of Multiphase-doped TiO₂ Nanotube Arrays Film By Anodizing

With the continuous development of global industrialization,people have to face the problem of pollution at the same time when people are enjoying the convenience of industrial development.The pollution problems of air and water have lead to a lot of health problems,so to solve environmental pollution problems was imminent.Titanium dioxide(TiO2)has attracted extensive attention of researchers because it can photocatalytic degrade various pollutants with no difference.However,these two problems of TiO2 semiconductor materials which limit its application can not be neglected.Firstly,the band gap of TiO2 semiconductor material is very wide,about 3.2 eV,the utilization rate of visible light is very low.Secondly,the recombination rate of photo-generated electron-hole pairs of TiO2 semiconductor materials is very high.In recent decades,researchers have done a lot of exploration mainly in the methods of modification and methods of preparation in order to solve these two problems.In this paper,95 vol%ethylene glycol,0.3 wt%NH4F and 5 vol%deionized water were elected as the based electrolyte system.The optimal anodizing time was got by adjusting the time of anodic oxidation at a certain voltage.ZnO-TiO2 nanotube array thin films and ZnO-Ag-TiO2 nanotube array thin films were prepared by one-step method using a numerical control double pulse power source by adjusting the concentration of Zn(NO3)2·6H2O and AgNO3 in the electrolyte.The morphology,phases,chemical composition and optical properties were investigated by SEM,TEM,XRD,EDS,UV-vis absorption spectroscopy and PL(photoluminescence).The photocatalytic properties were studied by degrading methylene blue under visible light,and the modification mechanism was also been discussed.The main experimental results are as follows:ZnO-TNTs were successfully prepared under optimized press condition,Zn dispersed on TNTs in the form of ZnO,ZnO concentration of 1 mM/L and reverse voltage of 5 V were the optimum parameters.The band gap of ZnO-TNTs was narrowed from 3.20 eV to 2.99 eV(0.21eV),and the amount of photogenerated electron-hole pairs was reduced significantly.The optimum degradation rate of methylene blue of ZnO-TNTs was 81.9%under visible light with the catalyst concentration of 1 cm2·ml-1,which was improved 11%than the undoped TNTs.ZnO-Ag-TNTs were successfully prepared by adjusting the concentration of AgNO3(0.2-0.8 mM)in the 5 vol%additive electrolyte of 1 mM/L Zn(NO3)2·6H2O and the reverse voltage(4-8 V).Ag is distributed in TNTs mainly in the form of dispersed phases and few in the form of Ag nanoparticles,the optimum process parameters were 1 mM ZnO+0.4 mM Ag with the reverse voltage of 5 V.The band gap of ZnO-Ag-TNTs was narrowed from 3.20 eV to 2.79 eV(0.41eV),and the recombination rate of photogenerated electron-hole pairs was significantly reduced.When the ZnO-TNTs catalyst concentration is 1 cm2·ml-1,the optimum degradation rate of methylene blue was 86%under visible light,which was 15.1%higher than that of undoped TNTs.ZnO-Ag-TNTs prepared by this one step method has good photocatalytic properties.