ZnPc/TiO2 composites for photocathodic protection of 304 stainless steel

Core-Shell Spheroid Structure TiO2/CdS Composites with Enhanced Photocathodic Protection Performance

In order to improve the conversion and transmission efficiency of the photoelectron, core-shell spheroid structure titanium dioxide/cadmium sulfide (TiO₂/CdS) composites were synthesized as epoxy-based coating fillers using a simple hydrothermal method. The electrochemical performance of photocathodic protection for the epoxy-based composite coating was analyzed by coating it on the Q235 carbon steel surface. The results show that the epoxy-based composite coating possesses a significant photoelectrochemical property with a photocurrent density of 0.0421 A/cm² and corrosion potential of -0.724 V. Importantly, the modified composite coating can extend absorption in the visible region and effectively separate photoelectron hole pairs to improve the photoelectrochemical performance synergistically, because CdS can be regarded as a sensitizer to be introduced into TiO₂ to form a heterojunction system. The mechanism of photocathodic protection is attributed to the potential energy difference between Fermi energy and excitation level, which leads to the system obtaining higher electric field strength at the heterostructure interface, thus driving electrons directly into the surface of Q235 carbon steel (Q235 CS). Moreover, the photocathodic protection mechanism of the epoxy-based composite coating for Q235 CS is investigated in this paper.

Progress in semiconductor materials for photocathodic protection: Design strategies and applications in marine corrosion protection

Metal protection of offshore equipment is very complicated owing to the complex marine environment. Photocathodic protection (PCP) is one of the popular research topics in marine metal protection. The protection efficiency of photoanode depends largely on the photoelectric properties of semiconductor materials, viz. the process of charge separation, charge migration, and light absorption. In this article, the enhancement strategies, photoelectrochemical properties, and electron transfer mechanisms of different composites for PCP were reviewed and highlighted. Some photoanodes with unusual and striking properties were emphasized. In addition, the outlooks and challenges of the application of PCP and the design of photoanodes materials are proposed.

A highly efficient In2S3/Ag2S/TiO2NTAs photoelectrodes for photocathodic protection of Q235 carbon steel under visible light

A novel In₂S₃/Ag₂S/TiO₂nanotube arrays (NTAs) was successfully fabricated by successive ionic layer adsorption and reaction method and electrochemical anodic oxidation method, and served as photoanode for photocathodic protection application. The micromorphologies, optical absorption properties, crystalline structure and elemental valence states of the composites were performed by field emission scanning electron microscopy, high resolution transmission electron microscope, UV-vis diffuse reflectance absorption spectra, x-ray diffractometer and x-ray photoelectron spectroscopy, respectively. The photocathodic protection performances of In₂S₃/Ag₂S/TiO₂NTAs on the Q235 carbon steel (CS) were also studied. The In₂S₃/Ag₂S/TiO₂nanocomposites show better photoelectrocatalytic and photocathodic protection performance than pure TiO₂NTAs. The photocurrent density of In₂S₃(9)/Ag₂S(8)/TiO₂photoelectrode coupled with Q235 CS reach 211μA cm^-2, which is about 4.5 times higher than that of TiO₂NTAs. The photogenerated potential of Q235 CS coupled to In₂S₃(9)/Ag₂S(8)/TiO₂under illumination shows a negative shift to -0.92 V versus SCE. Results indicate that the co-sensitization of In₂S₃and Ag₂S could extend the light absorption of TiO₂to the visible light range and enhance its photoelectric conversion efficiency.

Direct Z-scheme MgIn2S4/TiO2heterojunction for enhanced photocathodic protection of metals under visible light

To improve the photocathodic protection performance of traditional TiO₂photoanodes for metals, constructing a Z-scheme heterojunction is one of the most promising and creative strategies. Herein, we fabricated a novel Z-scheme MgIn₂S₄nanosheets/TiO₂nanotube nanocomposite through anodization and hydrothermal method. The optimized Z-scheme MgIn₂S₄/TiO₂nanocomposites exhibited stronger visible light absorption, higher separation efficiency of photoelectrons and photocathodic protection performances in comparison to pure TiO₂. The theoretical analysis and experimental results show that the Z-scheme heterojunction and oxygen vacancies jointly improved the separation efficiency of photogenerated electron-hole pairs and visible light absorption capacity, thereby improving the photoelectric conversion performance of the MgIn₂S₄/TiO₂nanocomposites. Furthermore, the influence of the precursor solution concentration on the photocathodic protection performances of the composites was investigated. As a result, when the concentration of magnesium source in the precursor solution was 0.06 mmol, the prepared MgIn₂S₄/TiO₂-0.06 displayed the best photocathodic protection performance. In addition, the hydroxyl radicals (·OH) generated in the electron spin resonance (ESR) experiment verified the Z-scheme heterojunction mechanism of the MgIn₂S₄/TiO₂composite, and also demonstrated the excellent redox performance of the composite. This work provides valuable reference for the construction of high-performance Z-scheme heterojunctions for photocathode protection of metals.