| Photoelectrochemical cathodic protection derived from a semiconductor photoelectric conversion prosess is a new method of controlling metal corrosion and has drawn high interest for corrosion resercher over the last decade.In the photoelectrochemical cathodic protection system,the photogenerated electrons from a semiconductor photoanode under light illumination are transferrd to a coupled metal and protect it from corrosion,which is energy saving,environment-friendly,and sustainable in comparison with traditional cathodic protection.A photoanode is a core part of a photoelectrochemical cathodic protection system.A TiO2 semiconductor is often used as a photoanode material in the system,which is non-toxic,stable,inexpensive,high catalytically active,and easy to prepare.However,TiO2 has a large band gap and its electron-hole pairs are easy to recombine,which weakens its photoelectrochemical cathodic protection effect.In view of these key issues,photosensitizers and electron transport materials were used to modify TiO2 nanotube films in this work to improve their visible light absorption and charge separation efficiencies.As a result,two modified composite films with significantly enhanced photoelectrochemical cathodic protection properties were obtained.Herein,the main contents and research progress are as follows:(1)A combined anodic oxidation,cyclic voltammetry electrodeposition,and continuous ion layer adsorption and reaction method was developed to fabricate a novel Bi2S3/reduce graphene oxide(rGO)co-modified TiO2 nanotube composite film for photoelectrochemical cathode protect applications.Bi2S3 is an ideal photo sensitizer,and its energy level matches that of TiO2,which can enhance the visible light absorption.Graphene is an excellent electronic conductor that is beneficial to electron transfer.After the TiO2 nanotube film was modified with rGO sheets and Bi2S3 nanoparticles,the visible light absorption and the electron-hole separation efficiency of the Bi2S3/rGO/TiO2 composite film were greatly improved.More importantly,under white light irradiation,the photocurrent density of composite film photoanode was up to 2000 ?A/cm2,which was 62.5 times that of the TiO2 nanotube film(32 ?A/cm2),and it could make the potential of the coupled 403 stainless steel(403SS)in a 0.5 mol/L NaCl solution negative shift by 490 mV from its free corrosion potential,indicating that the composite film had a significantly enhanced photoelectrochemical cathodic protection effect compared to the pure TiO2 film.(2)A novel CdSe/ZnIn2S4/TiO2 nanotube composite film with a cascade heterostructure was prepared by electrochemical anodization,hydrothermal reaction,and potentiostatic electrodeposition,and was well applied in photoelectrochemical cathodic protection.In this composite film,CdSe is sreved as a photosensitizer,ZnIn2S4 is an electron transport material,and the band positions of the three semiconductors are matched.The conduction band position is gradually dropped from CdSe to ZnIn2S4 to TiO2,which can form a cascade hetero structure and effectively promote the separation of the electron-hole pairs.Therefore,while the TiO2 nanotube film was modified by the CdSe nanoparticles and ZnIn2S4 sheets,the visible light absorption and the separation efficiency of electron-hole pairs of the composite film were greatly improved.Furthermore,the photocurrent density of the CdSe/ZnIn2S4/TiO2 composite film photoanode under white light irradiation reached 1000 ?A/cm2,and was 31 times higher than that of pure TiO2 nanotube film.The composite film irradiated with white light made the potential of 403SS in the 0.5 mol/L NaCl solution decrease by 440 mV from its corrosion potential.This result showed that the composite film had a more effective photoelectrochemical cathodic protection effect than the simple TiO2 film. |
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