Research progress of TiO2 photocathodic protection to metals in marine environment

Corrosion protection has become an important issue as the amount of infrastructure construction in marine environment increased.Photocathodic protection is a promising method to reduce the corrosion of metals,and titanium dioxide(TiO2) is the most widely used photoanode.This review summarizes the progress in TiO2 photo gene rated protection in recent years.Different types of semiconductors,including sulfides,metals,metal oxide s,polymers,and other materials,are used to design and modify TiO2.The strategy to dramatically improve the efficiency of photoactivity is proposed,and the mechanism is investigated in detail.Characterization methods are also introduced,including morphology testing,light absorption,photoelectrochemistry,and protected metal observation.This review aims to provide a comprehensive overview of Ti02 development and guide photocathodic protection.

Constructing Bi_(2)WO_(6)-decorated TiO_(2) composite films for photocathodic protection of 304 stainless steel

Bi_(2)WO_(6) nanoplate/TiO_(2) nanowire and Bi_(2)WO_(6) nanoflower/TiO_(2) nanowire composite films were successfully prepared using a hydrothermal method.The results show that the light absorption for Bi_(2)WO_(6)/TiO_(2) composite films is extended to the visible region after Bi_(2)WO_(6) nanoplates and nanoflowers are assembled onto TiO_(2) nanowires.Furthermore,Bi_(2)WO_(6) nanoflower/TiO_(2) nano wire composite film exhibits a better absorption property compared to Bi_(2)WO_(6) nanoplate/TiO_(2) nanowire film,which is mainly ascribed to the narrower bandgap of Bi_(2)WO_(6) nanoflower compared to that of Bi_(2)WO_(6) nanoplate.The photocurrent density for Bi_(2)WO_(6) nanoflower/TiO_(2) nanowire and Bi_(2)WO_(6) nanoplate/TiO_(2) nanowire composite films can reach 95 and 62.5 μA cm-2,respectively,which are much higher than that obtained for a pure TiO_(2) nanowire film(25 μA cm-2).Meanwhile,under illumination,the pure TiO_(2) nanowire,Bi_(2)WO_(6) nanoplate/TiO_(2) nanowire and Bi_(2)WO_(6) nanoflower/TiO_(2) nanowire films can reduce the potential of the coupled 304 stainless steel in 3.5 wt.%NaCl solution by 299,719 and 739 mV,respectively.Thus,Bi_(2)WO_(6) nanoflower/TiO_(2) nanowire film is found to provide the best effective photocathodic protection for 304 stainless steel.This work not only provides an example of shape-dependent photocathodic protection based on Bi_(2)WO_(6) but also opens up new possibilities to design an ideal microstructure on the basis of semiconductor materials for future applications of photocathodic protection.

One-dimensional Ag2S/ZnS/ZnO nanorod array films for photocathodic protection for 304 stainless steel

Highly ordered Ag2 S/ZnS/ZnO nanorod array film photoanodes were prepared on a Ti substrate for photocathodic cathodic protection.The results indicated that the photoresponse range of the Ag2S/ZnS/ZnO composite film was extended compared to those of the ZnO and ZnS/ZnO films,indicating its higher light absorption capacity.When the Ag2S/ZnS/ZnO composite film served as a photoanode,the film can provide the best effective photocathodic protection for 304 stainless steel in a 3.5 wt%NaCl solution under white light illumination compared to the ZnO and ZnS/ZnO films.Additionally,in comparison to pure ZnO film,the photocurrent for the ZnS/ZnO film remained the same without noticeable fluctuation after illumination for 1 h,indicating that the ZnS functionalization improved the stability by overcoming the photocorrosion effect of the ZnO photoanode under light irradiation.

Preparation of Ag@CuFe_(2)O_(4)@TiO_(2) nanocomposite films and its performance of photoelectrochemical cathodic protection

A Ag@CuFe_(2)O_(4)@TiO_(2) nanocomposite film with high performance of photogenerated cathodic protection was prepared by hydrothermal and photoreduction methods.The results showed that when the CuFe_(2)O_(4) hydrothermal reaction time was 6 h and the AgNO_(3) concentration was 0.1 M,the Ag@CuFe_(2)O_(4)@TiO_(2) nanocomposite material performed the best cathodic protection capability for 304 stainless steel(304SS).In this case,the protective potential achieved-930 mV(versus SCE)associated with the photocurrent density of 475μA/cm^(2),which was 14.8 times that of pure TiO_(2) nanowires.In the dark,the nanocomposite provided cathodic protection of up to 485 mV for 304SS.Due to the heterogeneous junctions at the two interfaces among the three kinds of nanocomposite materials,the build-in electric field was fabricated,which promoted the separation efficiency of photogenerated electrons and holes and effectively improved the photochemical cathodic protection of 304SS.