A novel CaIn2S4/TiO2 NTAs heterojunction photoanode for highly efficient photocathodic protection performance of 316 SS under visible light

Abstract

Designing heterojunction photocatalysts with matched band structure and good interface contact is an effective method to improve the photoelectrochemical activity. Herein, novel CaIn2S4/TiO2 nanotube arrays (NTAs) heterojunction photoanodes were successfully prepared by electrochemical anodization and hydrothermal method. The microstructures, compositions, crystal structures, chemical valence states and light absorption performances of the composites were evaluated by field emission scanning electron microscopy, energy dispersive x-ray spectroscopy transmission electron microscope, high-resolution transmission electron microscope, x-ray diffractometer, x-ray photoelectron spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), respectively. The photocathodic protection performances of CaIn2S4/TiO2 composites for 316 stainless steel (SS) and the influences of the CaIn2S4 content on the performances were studied. The microstructural examination revealed the uniform doping of CaIn2S4 nanofragments on the TiO2 NTAs, and the composite was made up cubic CaIn2S4 and anatase TiO2. The photogenerated electrons were transferred from the TiO2 to CaIn2S4 at the interface of the composite. Compared with pure TiO2 NTAs, CaIn2S4/TiO2 NTAs exhibited better photocathodic protection performance for 316 SS under visible light. Potential drop reached 0.78 V versus saturated calomel electrode for the 316 SS coupled with CaIn2S4/TiO2 NTAs. The photocurrent density of the 316 SS coupled with the composite photoanode (235.4 μA cm–2) was 17.4 times that of TiO2. The improved photocathodic protection property of CaIn2S4/TiO2 NTAs was ascribed to the enhanced separation efficiency of the photogenerated carriers and the strong visible light absorption of the material. The CaIn2S4/TiO2 NTAs exhibited continuous protection of the 316 SS for more than 12 h even in the dark. Therefore, the CaIn2S4/TiO2 NTAs heterojunction composite is an outstanding and efficient photoanode for the photocathodic protection of metals.

A 3D hierarchical TiO2/CaIn2S4/C3N4 arrays photoanode with dual-heterojunction for enhanced photoelectrochemical performance

“…After Lei et CIS heterojunction, the band alignments of TiO 2 and CIS lead to the establishment of a staggered type-Ⅱ heterojunction due to the relatively negative conduction band potential of CIS, which would enhance the visible-light response of TiO 2 and promote efficient charge transfer and separation, as demonstrated in previous works [22].…”

Review of TiO2-Based Heterojunction Coatings in Photocathodic Protection

“…Water is employed as the solvent. The morphology and size of the coatings can be controlled by adjusting the reaction temperature, reaction time, precursor solution concentration, and other experimental parameters. − Wang et al prepared FeS 2 /TiO 2 heterojunction coatings through the hydrothermal method. Scanning electron microscopy (SEM) results indicated that the prepared FeS 2 adhered to TiO 2 NTs.…”

A highly efficient In2S3/Ag2S/TiO2 NTAs photoelectrodes for photocathodic protection of Q235 carbon steel under visible light

“…Photoelectrochemical performances of the composites were characterized by a CHI 760E electrochemical workstation (Chenhua Co., Ltd, China). The experimental setups for measuring open circuit potential (OCP), Tafel curves, electrochemical impedance spectroscopy (EIS) and photocurrent densities was the same as the devices reported previously [32]. The Mott-Schottky (M-S) plots and i-V curves were measured in 0.1 M Na 2 SO 4 solution using a conventional three-electrode system, in which Pt electrode was used as the counter electrode and a saturated calomel electrode (SCE) was used as the reference electrode, respectively.…”