Photoelectrochemical Cathodic Protection of Stainless Steel using W- and Cr-Doped/Codoped TiO <sub>2</sub> Nanotube Thin Film Photoanodes
Mohamad Mohsen Momeni, Majid Motalebian, Yousef Ghayeb, Masoud Atapour
Abstract
TiO 2 nanotubes have been co-doped with chromium and tungsten by electrochemical anodization. Tungsten and chromium single doped and pure TiO 2 nanotubes have also been synthesized. Many methods have been used to characterize the products obtained. Following doping and co-doping of TiO 2 , the optical absorption edges are considerably red shifted to the visible region due to the induced impurity states within the band gap. The samples prepared were used as photoanodes for photocathodic protection in order to retard 403 stainless steel corrosion. Chromium and tungsten co-doping was found to enhance the visible photocatalytic activity of the resulting TiO 2 nanotubes. Better photoelectrochemical performance and photocathodic protection properties were shown by (Cr-W)-co-doped TiO 2 , Cr-doped TiO 2 and W-doped TiO 2 samples compared with the undoped TiO 2 nanotubes. The best co-doped TiO 2 sample showed a photocurrent density, which was 2.6 times higher than that of the undoped TiO 2 . Under light illumination, the (Cr-W)-co-doped TiO 2 photoelectrode decreased the potential of the coupled 403 stainless steel in a 3.5 wt. % NaCl solution to 400 mV, indicating an effective photocathodic protection. The synergetic effects of co-doping by chromium and tungsten may be responsible for the enhanced visible photocatalytic activity.