Photoelectrocatalytic Performances Of TiO₂ Nnaotube?sTNT? And Ag Modified STNT?Ag/sTNT? Synthesized By Secondary Anodization

For decades,TiO2 nanotube(TNT)has attracted considerable attentions due to its high surface-volume ratio and reducing grain boundaries.Photoelectrocatalytic technology which exhibits both the advantages of photocatalysis and electrocatalysis is a new research field that rises in recent years.The combination of TNT and photoelectrocatalytic technology has been widely applied in the degradation of organic pollutants,which has shown the broad application potential in the environmental protection.However,there are many key issues need to be stressed in photoelectrocatalytic technology,pivotally including the theoretical study of photoelectrocatalytic mechanism.Basic study on photoelectrocatalytic properties and mechanism provide fundamental basis for designing reactor and photoelectric material and improving the efficiency of photoelectrocatalysis.In the present study,TiO2 nanotubes(sTNT)are prepared by the secondary anodization method.The structure and morphology of sTNT were characterized by using XRD?XPS?SEM and DRS measurements.The photoelectrocatalytic performance of sTNT was analyzed by the degradation reaction of rhodamine B(RhB)under the illumination of simulated solar light.By controlling the deposition time and photoreduction time,Ag nanoparticles were deposited on the sTNT to synthesize the Ag/sTNT.The effect of the noble metal on the photoelectrocatalytic process was investigated.The results obtained are as follows:(1)TiO2 nanotube with homogenous surface was synthesized by the secondary anodic oxidation method with the nanotube length up to 9 ?m and the diameter of 70-80nm;(2)When applying a bias of +0.6 V vs Ag/AgCl,sTNT exhibited optimal photoelectrocatalytic activity,which was 2.93 folds higher than the photocatalytic process;(3)With the deposition and photoreduction time of 3 hours and 5 min respectively,the sample Ag/sTNT-3-5 exhibited optimal photocatalytic activity;(4)Ag/sTNT-3-5 remains stable in photoelectrocatalytic degradation process.At a bias of-0.6 V vs Ag/AgCl,Ag/sTNT-3-5 showed optimal photoelectrocatalytic activity and the pollutant could be completely degraded in 120 min.The photoelectrocatalysis mechanism is proposed that the introduction of bias potential could facilitate separation of the conduction band electrons and the valence band holes reaching to optimal transfer equilibrium.The doping of Ag further enhanced the electrons transferred to Ag to produce active species and enhance photoelectrocatalytic activity.Innovation of this paper is:(1)Photoelectrocatalytic mechanism of titanium dioxide nanotube in degradation of RhB dyes was set forth for the first time by analysing the separation of Ti substrate on the carriers of conduction band and valance band in sTNT;(2)By depositing noble metals,the effect of the noble metal on the photoelectrocatalytic process was investigated.