Construction Of Dopamine-modified Photo-anode And Photocathodic Protection Research

Marine corrosion is a serious threat to the development of marine resources,which bring great loss every year and causing serious security risks every year.In order to reduce loss caused by corrosion,a lot of research has been done on anticorrosion materials and techniques with excellent corrosion resistance.304 stainless steel（304SS）is widely used in various marine engineering on account of its excellent corrosion resistance.However,304SS is pitting by reason of the action of chloride ions in highly corrosive marine environments,which leads to the destruction of the passive film to threat the all-over structure.Cathodic protection method is one of the common methods of marine corrosion control,mainly using the impressed current method and the sacrificial anode method.However,the waste of resources and ecological impact caused by these methods can’t be ignored.The corrosion protection of the metal is promoted effectively by the photosensitive cathodic protection system without causing environmental pollution.Under the light,the surface potential of steel was reduced due to the electrons generated by the semiconductor,as to achieve the purpose of protecting it.This method has become an acclaimed strategy to solve the corrosion problem.In order to solve the problems of complex preparation methods and poor stability of photosensitive cathodic protection system,the photoanode was modified by polydopamine（PDA）,and good light absorption performance,adhesion,stability and electronic transmission performance was used to the protection ability of photoanode for 304SS.The optical properties,electrochemical properties and cathodic protection mechanism of composite photoanode were studied.1.Firstly,TiO₂ was modified by PDA with good visible light absorption performance.TiO₂ Nanoarray（TiO₂NTs）coated with PDA coating of different thickness were prepared by combining PDA with TiO₂NTs and controlling the load of PDA on TiO₂ NTs by controlling the composite time.It was observed by scanning electron microscope（SEM）that PDA coating thickened gradually on TiO₂ NTs with the increase of composite time.Open-circuit potential（OCP）test showed that TiO₂ NTs modified by PDA had good photocathodic protection performance,and PDA/TiO₂photoanode with PDA loading time of 4h had the best performance.Photoluminescence（PL）spectrum and electrochemical impedance spectroscopy（EIS）showed that PDA combination reduced the secondary recombination of photogenerated carriers and improved the separation efficiency of photogenerated electrons and holes.The cathodic protection mechanism of PDA/TiO₂ photoanode was analyzed by the energy band matching of PDA and TiO₂.2.Secondly,based on the adhesion properties of PDA,Ag nanoparticles were loaded on the surface of PDA/TiO₂ by ion chromatography adsorption.It was observed by SEM that TiO₂ NTs with PDA coating was uniformly adhered to Ag nanoparticles,while TiO₂ NTs without PDA coating was not loaded with Ag nanoparticles.The i-V curve was obtained by linear sweep voltammetry,which showed that the photocurrent conversion potential of Ag-PDA/TiO₂ photoanode was negative,and the photogenerated electrons had strong reducing property.OCP test showed that the PDA/TiO₂ photoanode uniformly loaded with Ag nanoparticles had good photocathodic protection performance.PL spectra and EIS show that the loading of Ag nanoparticles improves the photoelectric properties of the materials.The mechanism of surface plasmon resonance（SPR）effect of Ag nanoparticles on photocathodic protection was investigated.3.Finally,based on the based on the adhesion properties of PDA,PDA/CdSe core-shell structure is constructed.PDA/CdSe photoanode was prepared by coating PDA on the surface of CdSe.The surface morphology of PDA/CdSe was observed by SEM,and the distribution of elements on the surface was characterized by Mapping.OCP test shows that CdSe coated with PDA has better stability and photocathodic protection than without PDA.Uv-vis showed that the combination of PDA enhanced the visible light absorption performance of CdSe.The photogenerated carrier separation rate of PDA/CdSe was investigated by PL spectra and EIS,and the inhibition of PDA on CdSe photocorrosion was investigated.