Control The Surface Ti³⁺ Content Distribution To Prepare Visible Light-responsive Black Titanium Dioxide

Titanium dioxide(TiO2)has been widely investigated due to the high photocatalytic activity for environmental cleanup.However,UV light excitation should be necessary to show its photocatalytic activity because of large band gap(Band gap:Ebg>3.0 eV).Therefore,indoor light or visible region of solar light cannot be used for the light source of TiO2 photocatalytic reactions.The black TiO2 obtained by hydrotreatment has been studied as a photocatalytic material in recent years,black TiO2 became a hotspot of research because it can absorb sunlight and indoor light.Though those reports about black TiO2,I decided to focus on the relationship between the content and distribution of Ti3+ and the photocatalytic activity under visible light.I used a variety of methods to prepare black TiO2 samples with controlled Ti3+ content and Ti3+ distribution.After that,the physical and chemical properties of the black TiO2 samples were analyzed by XRD,XPS,SEM,HR-TEM,BET and UV-vis.The photocatalytic decomposition of isopropanol was used to analyze the photocatalytic activity of black TiO2 samples under visible light irradiation.Finally,black TiO2 samples with high photocatalytic activity can be prepared by those conclusions.The investigation was divided into the following three parts:(1)Black Ti02 particles with no layered structure on the surface were prepared from TiH2 particles by chemical gel oxidation method,and the Ti3+ content was controlled by different time or different amount of the calcined precursor.The black TiO2 particles have no layered structure on the surface which can respond to visible light and exhibit photocatalytic activity.However,because the size of the black TiO2 particles prepared by the chemical gel method is too large and the adjustment of the Ti3+ content is not stable enough,other methods were used to prepare black TiO2 in the following study.(2)Black TiO2 samples with controlled Ti3+ was prepared by atmospheric pressure oxidation using black TiO2 with high reduction as raw material.After analysis,it was found that the layered structure of the black TiO2 particles disappeared after heat treatment and the Ti3+ content decreased.The change in the proportion of Ti3+ on thesurface of the black TiO2 sample caused the black TiO2 sample to exhibit different absorption of visible light,bandgap energy,and the fate of photoexcited electron-hole pairs.Finally,the results of photocatalytic activity and apparent quantum efficiency showed that under visible light irradiation,the proportion of Ti3+ on the surface of black TiO2 samples decreased after heat treatment,and the photocatalytic activity and the apparent quantum efficiency increased first and then decreased.The results of this study showed that by controlling the proportion of Ti3+ on the surface,the photocatalytic activity of black TiO2 particles under visible light can be improved.(3)Black TiO2 samples with uneven distribution of Ti3+ on the surface were prepared by ball milling.After analysis,it is proved that the regulation of Ti3+ distribution will affect the photocatalytic activity of black TiO2 under visible light,but the reasons for its further need to continue to be studied.