Preparation And Photocatalytic Properties Of B,N Doped TiO₂ Nanotube Arrays

Organic pollutants are great threats to our health.In recent years,photocatalytic technology have received great atterntion.However,search for high efficient photocatalyst is still a key for photocatalytic technology.TiO₂ are one of the most widely used photocatalys.However,they are not responsible to visible light,which limited their application.Nonmetal doping TiO₂ is reported that they can improve the visible light catalytic activity because new intermediate energy level can be formed between the valent and conduction band of TiO₂.Traditional method for the preparation of nonmetal doped TiO₂ is very complex and expensive.In order to solve these problems,in this paper we study the preparation method and choose different cheap N source to prepare nonmetal doping TiO₂ nanotube arrays（TiO₂ NTs）.（1）B doped TiO₂ NTs:A two-step anodic oxidation method was used to prepare TiO₂ NTs by electrochemical anodic oxidation method.Then B（c）-TiO₂ NTs were perepared by a second anodic oxidation method in different concentration of boric acid solution.X-ray diffraction（XRD）measurement showed that the TiO₂ sample is anatase type.Field emission scanning electron microscopy（FESEM）found that the doping of B into TiO₂ NTs did not distroy the original structure of nanotube arrays.X-ray photoelectron spectroscopy（XPS）found that the dopping Bs are in interstitial boron site of（Ti-O-B）.We found that when boron source is 0.4 mol/l,the prepared sample shows the best photoelectronic properties whose photocurrent density is 7.5times that of pure TiO₂ NTs.The photocatalytic degradation rate for 4NP were 7.9times that of TiO₂ NTs.Photoactive species is studied to be·O₂^-and h⁺by adding cavenger.（2）N doped TiO₂ NTs:N doped TiO₂ NTs were prepared by wet chemical impregnation method by dipping TiO₂ NTs in different N sources（ammonia,ethylenediamine and urea）.X-ray diffraction（XRD）analysis showed that anatase TiO₂can be obtained in all the N sources.Field emission scanning electron microscopy（FESEM）found that no obvious change of original morphology of TiO₂ NTs using ammonia and ethylenediamine.However,when urea was used as N source,double walled TiO₂ NTs arrays were abtained.X-ray photoelectron spectroscopy（XPS）shows that N atom replace the O atom site.There are O-Ti-N bonds in the sample.We found that when ethylenediamine was used as N sources,the obtained sample shows the highest photocatalytic performance for photocatalytic degradation of 4NP.When the preparation concentration is 1.0 mol/l ethylenediamine,56.6%,which improved 30%compared with that of pure TiO₂ NTs.·O₂^-and·OH were found to be the main photoactive species during the photo degradation reaction.