Preparation And Characterization Of Plasma Electrolytic Oxidation Photocatalyst Coatings On Titanium Substrate

Catalytic science is an effective way to solve the problems of environmental pollution and energy crisis.In general,photocatalysis reaction is heterogeneous.As one of the most commonly used photocatalysts,titanium dioxide powder has high catalytic activity and high stability.However,it's further application has been limited due to the difficulty of reutilization and it's necessary to be immobilized.Coatings catalysis can overcome the defects.For the conventional coating catalyst preparation method,most of the active components are not easily doped,and the active components are not strongly bonded to the substrate after doping.Plasma electrolytic oxidation is a new method to prepare catalytic coatings,and this method is easy to operate and environment-friendly.The doping of active components can be achieved through the regulation of electrical parameters.The active components doped in situ grow well with the substrate.This kind of method presents good prospects in the preparation of coating catalysts.In this work,commercial pure titanium?TA1?was used for the preparation of photocatalytic titanium dioxide films by plasma electrolytic oxidation.Properties of the films were characterized.And catalytic activity of the films was also discusseded by degradation of methylene blue under ultraviolet light irradiation.Meanwhile,the effect of hydrothermal treatment on the WO₃/TiO₂ films was also studied.The experimental results showed that preparation process parameters had an influence on the films.The modified TiO₂ films doped with different elements and ratio of active components could be acquired by adjusting the electrical parameters in the plasma electrolytic oxidation process.The ratio of W:Zn decreased from 7.22 to 2.26,accompanied by the increase of reaction voltage and the prolongation of reaction time.Increasing the preparation voltage and prolonging the reaction time could improve the content of active components in the films.And all elements doped in the films were uniformly distributed throughout the films.After doping with ZnO,the absorbance peak of the films increases,which is more easily excited under irradiation.The photocatalytic degradation of methylene blue showed that the catalytic activity was improved of the films doped with ZnO.The remove rate increased24.7%,comparing with the undoped ZnO coating.And the photocatalytic performance of the films was improved by increasing the preparation voltage and prolonging the reaction time.Surface morphology of the WO₃/TiO₂ coatings had a signifinicant change after hydrothermal treatment with sodium copper chlorophyllin.A thin layer of strip or flake structure was formed on the surface of WO₃/TiO₂ coatings,and it was evenly distributed throughout the whole coatings.X ray diffraction spectra showed that anatase TiO₂crystallinity became better after hydrothermal treatment.With the increase of the hydrothermal treatment temperature,the crystallization performance of anatase TiO₂ became better.UV Vis diffuse reflectance spectroscopy showed that the absorption peak appeared in the optical area at wavelength greater than 400 nm.And the peak value of absorption increased at first and then decreased with the increase of hydrothermal treatment temperature,the highest peak was at 140?.