Study On Preparation Of Modified TiO₂ Nanomaterials And Its Photoelectrochemical Cathodic Protection Perfermance

The corrosion of metal materials causes huge losses in the development of social economy.The authoritative corrosion report shows that the annual corrosion loss accounts for 2-5%of the GDP per year.Marine exploitation is an important means to solve the problem of resource and energy shortage in the 21st century.Since Fujishima and Tsujikawa discovered the photoelectric chemical cathodic protection of TiO2 thin film on metal,a new and green environmental protection technology,using light energy to achieve the photoelectric chemical cathodic protection of metal has aroused extensive interest of scientists.However,the optical defects of TiO2 materials limit the practical application of photochemical cathodic protection.Firstly,TiO2 has a wide band gap,Eg= 3.2ev.Only the ultraviolet light can excite electrons in the valence band of TiO2,and the energy in the ultraviolet spectrum only accounts for 5%,so the light energy utilization rate is very low.Secondly,the photoexcited electron-hole of TiO2 material is easy to compound,which cause low quantum efficiency and poor photoelectric chemical cathodic protection effect.Moreover,in the absence of light,TiO2 has no cathodic protection effect on metal materials.On the basis of previous studies,this paper continues to explore the modification of TiO2 to improve the photoelectric chemical cathodic protection effect:(1)The FeS2/TiO2 nanocomposite thin film has been prepared by hydrothermal deposition with FeS2 nanoparticles on TiO2 thin film substrate.Material characterization such as XRD,XPS,EDS and electrochemical methods such as open-circuit potential time curve,photocurrent density time curve and tafel polarization curve were used to evaluate the photoelectric conversion ability and photochemical cathodic protection performance of FeS2/TiO2 nanocomposite film.Compared with pure TiO2,the FeS2/TiO2 nanotube array composites film greatly improves the photocathodic protection performance of 304 stainless steel.Under visible light irradiation,the open-circuit potential of 304 stainless steel coupled with the composite material can be reduced to about-700 mV,and the electrode potential of the stainless steel can still be maintained at-400 mV when the light is off,that is,the composite material FeS2/TiO2 can still play an electrochemical cathodic protection role in the dark.(2)AgBiS2/TiO2 nanocomposite thin film materials were prepared by depositing AgBiS2 nanoparticles on TiO2 thin film substrate by continuous ion-layer adsorption reaction.Material characterization such as XRD,XPS,EDS and electrochemical methods such as open-circuit potential time curve,photocurrent density time curve and tafel polarization curve were used to evaluate the photoelectric conversion performance and photoelectrochemical cathodic protection performance of AgBiS2/TiO2 nanocomposite film.Compared with pure TiO2,the modification of AgBiS2 nanoparticles on the surface of TiO2 nanotube array film greatly improves the photogenerated cathodic protection performance of 304 stainless steel.Under visible light irradiation,the open-circuit potential of 304 stainless steel coupled with the composite material can be reduced to about-950 mV,and the electrode potential of the stainless steel can still be maintained at-820 mV after the light is closed,that is,AgBiS2/TiO2 composite material can still play a photocathodic protection role in dark.