Preparation Of TiO₂ Nanotube Arrays Modified By Metal Indium Sulfide And Study Of Their Photogenerated Cathodic Protection Performanc

The problem of marine metal corrosion is one of the important constraints for China to build a powerful marine country.Therefore,human beings have developed a variety of methods to inhibit metal corrosion.Among them,photogenerated cathode protection technology has been widely studied by researchers at home and abroad in recent years.TiO₂is one of the most commonly used optoelectronic materials due to its nontoxic,low cost,excellent photoelectric conversion performance and chemical stability.However,TiO₂ has a wide band gap,light absorption is limited to the ultraviolet region,and the utilization efficiency of solar energy is very low.Meanwhile,the recombination rate of photogenerated electron-hole pairs excited in TiO₂ is high,and cannot provide continuous and effective protection for metals in the absence of light.These characteristics seriously limit the practical application of TiO₂ materials in the field of metal corrosion protection.In order to solve the above problems,in this work,metal indium sulfide semiconductors with good visible light response were combined with TiO₂ semiconductors to obtain CaIn₂S₄/TiO₂ and MgIn₂S₄/TiO₂ nanocomposites,which effectively improved the photoelectric chemical activity of TiO₂.In this paper,the tightly aligned TiO₂ nanotube arrays were prepared on the surface of titanium foil by electrochemical anodization,and then two novel heterojunction nanocomposites were successfully prepared by loading CaIn₂S₄ nanofragments and MgIn₂S₄ nanosheets on the surface of TiO₂ nanotube arrays.The structure information and photoelectrochemical properties of nanocomposites were studied,and their protective effects on 316 stainless steel and Q235 carbon steel were explored.The photoelectric conversion properties of the prepared CaIn₂S₄/TiO₂ and MgIn₂S₄/TiO₂ nanocomposites were compared.Since the direct Z-scheme heterojunction in the MgIn₂S₄/TiO₂ nanocomposites had stronger separation ability for photogenerated electron-hole pairs than the traditional II-scheme heterojunction,the MgIn₂S₄/TiO₂nanocomposites showed more excellent photogenerated cathodic protection effect than the CaIn₂S₄/TiO₂ nanocomposites,and the modification effect of the MgIn₂S₄ semiconductor on the TiO₂ semiconductor material was further improved.The main research contents and results are as follows:（1）CaIn₂S₄ nanofragments were loaded on the surface of TiO₂ nanotube arrays by hydrothermal method,and CaIn₂S₄/TiO₂ heterojunction photoanode was successfully obtained.The photocathodic protection performance of CaIn₂S₄/TiO₂ composite on 316stainless steel and the influence of CaIn₂S₄ content in the composite on its photoelectrochemical performance were studied.The results showed that after CaIn₂S₄composite TiO₂,the visible light absorption of the composite material was significantly enhanced,and its photoelectric chemical activity was greatly improved.Compared with pure TiO₂ nanotube arrays,CaIn₂S₄/TiO₂ composite exhibited better photocathodic protection for 316 stainless steel under visible light.The results showed that the CaIn₂S₄/TiO₂-B nanocomposite exhibited the best photocathodic protection performance when the amount of calcium source in the precursor solution was 0.22 mmol.The potential drop of CaIn₂S₄/TiO₂ composite coupled with 316 stainless steel reached 0.78 V,and the photocurrent density(235.4μA cm^-2)was 17.4 times that of pure TiO₂.（2）MgIn₂S₄ nanosheets were loaded on the surface of TiO₂ nanotube arrays by hydrothermal method to prepare direct Z-scheme heterojunction MgIn₂S₄/TiO₂nanocomposites.The photocathodic protection performance of MgIn₂S₄/TiO₂heterojunction composite for Q235 carbon steel and 316 stainless steel was studied.The effect of precursor solution concentration on photoelectric conversion performance of composites was investigated.The results showed that compared with pure TiO₂ nanotube arrays,MgIn₂S₄/TiO₂ heterojunction composite had wider spectral response range and higher carrier separation efficiency.When the amount of Mg source in the precursor solution was 0.06 mmol,the prepared MgIn₂S₄/TiO₂-0.06 nanocomposites exhibited the best photoelectric chemical properties.Under visible light irradiation,the photocurrent density of MgIn₂S₄/TiO₂-0.06 nanocomposite coupled with Q235 carbon steel was 507μA cm^-2,about 42 times higher than that of TiO₂.In addition,compared with CaIn₂S₄/TiO₂nanocomposites,the photocurrent density of MgIn₂S₄/TiO₂-0.06 nanocomposites coupled with 316 stainless steel was 401.2μA cm^-2,which was higher than that of CaIn₂S₄/TiO₂nanocomposites under the same conditions.MgIn₂S₄/TiO₂ nanocomposites showed more excellent photogenerated cathodic protection effect.