In order to obtain TiO2 with high photocatalytic activity,a cathode reduction was used to dope I 7+ and I5+into TiO 2 nanotubes of anodized Ti in C2H2O4·2H2O+NH4F electrolyte.SEM images show that the anodization method integrated the preparation with the doping process,which for nonmetals-doping is advantageous to maintain the morphological integrity of TiO2 nanotubes. I7+-I5+-doping enhances the UV response of TiO 2 and result in a red-shift.Under UV/visible irradiation,a I7+-I5+-doped sample(400°C)showed the highest Iph and photocatalytic efficiency.A part of I - in the I7+-I5+-doped sample is involved in the UV re-sponse,the red-shift and the higher Iph.
In order to investigate the catalytic performance of anodic TiO2 nanotubes and their practical application in the treatment of refractory microcystins(MCs) in natural-water samples,TiO2 nanotubes of diameter of 50-80 nm were fabricated by anodization in C2H2O4·2H2O containing NH4F.Under irradiation with natural sunlight,MC-LR was totally degraded after 1 d using the anodic TiO2 nanotubes.In contrast,the removal efficiency without TiO2 nanotubes was as low as 47.7% within 20 d.In addition,a mixture of anatase and rutile TiO2 gave higher photocatalytic activity than the single phase did.The pH also influenced the adsorption capacity of the TiO2 nanotubes.The order of MC-LR degradation efficiencies at different pH values was 3.5 > 8.0 > 10.0.After five repeated experiments on the degradation of MC-LR for 7 h,the degradation efficiency was still stable.
