Preparation And Photogenerated Cathodic Protection Of Multi-modified TiO₂ Nanosheets

It is a promising green anticorrosion technology to realize photogenerated cathodic protection of metals by utilizing the excellent photoelectrochemical properties of titanium dioxide.Anatase TiO2 dominant with(001)facets has been extensively studied for its high photocatalytic activity.However,the absorptive efficiency of pure TiO2 to solar light is extremely low.Furthermore,photogenerated electrons and holes are easy to recombine,these result in low quantum efficiency of titania that seriously limits its application.In order to improve the performance of photogenerated cathodic protection,a series of modified TiO2 composites were fabricated by quantum dot deposition,narrow bandgap semiconductor composites and doping appropriate carrier transport materials.The main research contents are as follows:(1)TiO2 nanosheets with(001)facets dominant and TiO2/graphene composites were prepared by hydrothermal method.PbS and CdS quantum dots were deposited on the surface of TiO2/graphene composites by a sonication-assisted successive ionic layer adsorption and reaction method.The samples co-deposited with PbS and CdS quantum dots exhibit the best optical absorption properties.The effective separation of electrons and holes in hybrid semiconductors is promoted by the electric field of p-n junction at the interface of TiO2/PbS and the CdS/PbS.The photocathode protection performance of GT/PbS/CdS composite semiconductor for 304 stainless steel is greatly improved.In addition,the electrochemical oxidation and reduction of PbS can discharge and charge photoexcited electrons in light or darkness,which can prolong the photochemical protection time in dark state.(2)TiO2 nanosheets were prepared by C3N4 template method.Then the graphene and MoS2 semiconductor were doped by simple hydrothermal method.The optical absorption range is extended from ultraviolet to visible through the composite sample of narrow bandgap semiconductor MoS2.The composite samples doped with 10 wt%MoS2 exhibited the best photochemical protection performance,which was mainly manifested in the high photocurrent density,the shift of corrosion potential to the corrosion resistance zone and the remarkable improvement of corrosion morphology for 304 stainless steel.Highly close interface contact between MoS2 and TiO2 can promote the effective separation of photogenerated carriers.The high electron mobility of graphene provides a transfer channel for photogenerated electrons and effectively inhibits the recombination of photogenerated electron holes.(3)TiO2 nanosheet arrays with highly reactive(001)facets grown on CFs were synthesized by hydrothermal method.Subsequently,Ag2S quantum dots were uniformly deposited on the surface of TiO2 nanosheets by continuous ion layer adsorption and reaction technology.The CFs-TiO2-Ag2S composite semiconductor material deposited by six times quantum dots has the best photoelectrochemical corrosion protection effect.This is mainly due to the fact that carbon fibers with high electron mobility provide transmission channels for photoexcited electrons and reduce the resistance of electron migration.The Schottky barrier formed at the semiconductor/metal interface and the increase of electric field intensity at the semiconductor/electrolyte interface promote the effective separation of photoexcited carriers,which can improve the quantum efficiency and realize the photogenerated cathodic protection effect.