Constructing Tubular Nanocomposites And Photoinduced Cathodic Protection Performance Investigation

The behaviour of metals in the oceans in relation to corrosion prevention and control is essential for a sustainable society.Quantum dots with superior photoelectric conversion efficiency present a brilliant moment for the construction of internal electric field heterojunctions for photogenerated cathode protection.In this paper,CuInS₂/TiO₂Mn In₂S₄/TiO₂and FeIn₂S₄/TiO₂nanocomposite thin film materials were designed to study the photocathodic protection system for metal corrosion prevention and control.The main contents and research progress are as follows:（1）TiO₂nanotubes grown vertically on the Ti substrates were modified via electrochemical oxidation and solvothermal pathway to sensitize with CuInS₂quantum dots.Compared with pure TiO₂,the modification improves sunlight absorption efficiency and provides photoelectron cathodic protection to the 304 stainless steel（304 SS）.Through 9 hours solvothermal reaction,the CuInS₂/TiO₂exhibited an excellent property when the sunlight irradiation.Its mixed open circuit potential was negatively shifted to-0.99 V,at the mean time with a stable photocurrent density(118μA·cm^-2).The results indicate that CuInS₂and TiO₂established a p-n heterojunction with well-matched energy level,which can effectively facilitate the carrier separation and retain the strong redox capbility of photo-induced electrons and holes.（2）Depositing two-dimensional Mn In₂S₄nanoflakes onto the TiO₂nanotubes through hydrothermal method.By altering the concentration of ingredients used in the experiment,the photocathodic protection effects of different samples are investigated sequentially.The optimal 2D Mn In₂S₄/TiO₂nanocomposite material decreased the coupled photo-induced potential by 0.53 V.The photo-generated current density stabilized around 180μA·cm^-2.The possible strengthening mechanism is obtained:n-n type heterojunction with good band matching gradient formed at the interface will accelerate the interface transfer of photocarriers,maintain high photoelectric conversion efficiency,and provide excellent corrosion protection for 304 SS.（3）FeIn₂S₄/TiO₂nanocomposite thin film materials with favourable protection properties were prepared by depositing FeIn₂S₄on TiO₂through hydrothermal method,and the growth time of FeIn₂S₄was altered under the premise of controlling the molar concentration of the raw material.After various electrochemical tests with 304 SS,FeIn₂S₄/TiO₂samples exhibited different corrosion control effects.In a 3.5 wt%Na Cl solution,the open circuit potential drop of the FeIn₂S₄/TiO₂protection system achieved-0.90 V and the photoinduced current density stabilized at approximately 114μA·cm^-2for a growth time of 3 h,both far higher than the potential drop（-0.53 V）and current density(30μA·cm^-2)values of TiO_2。Therefore,the FeIn₂S₄/TiO₂composite protection system provides superior and efficient photoelectrochemical cathodic protection for304 SS.