Preparation And Visible Light Photocatalytic Property Of Modified Brown Nano TiO₂

TiO₂ nanomaterials have become one of the focal points in the field of photocatalysis in recent years due to their characteristics of low cost,high efficiency,high chemical stability and light resistance.However,the wide band gap allows the traditional pure TiO₂ to absorb UV light only,while the high compound rate of electron-hole results in the low quantum efficiency.In order to solve the above two problems,researchers modified it in different ways.Sol-gel method has become one of the most common preparation methods of modified nano Ti O₂ in recent years because of its easy controllable process and the simple preparation technology,and it can obtain the nanoparticles which are homogeneous and has high purity,large specific surface area,and small size.However,the traditional sol-gel method has the disadvantages of tedious process and long preparation time,and the researched preparation temperature is generally higher which will cause the particles to reunite easily.In this paper,a simple synthesis method at low temperature was studied,and the TiO₂ was modified by doping metal ions,non-metal ions and forming complexes.The synthesis method was simple and mild,and the photocatalytic degradation or photocatalytic hydrogenation efficiency under visible light of modified TiO₂ was improved,which was of great significance to solving the problem of the current environmental pollution and energy depletion.The main contents of this paper are as follows:?1?The preparation of Fe-TiO₂ nanomaterials and their photocatalytic degradation performanceNano TiO₂ were modified by doping metal ion with Fe?NO₃?₃?9H₂O as source of iron,and the Fe-TiO₂ brown nano photocatalysts with visible light absorption,small grain size?5.6⁶.6 nm?and high specific surface area(191²23 m²?g^-1)were synthesized by one-step modified sol-gel method at low temperature.It was shown that Fe was successfully doped into the TiO₂ lattice with Fe³⁺and Fe²⁺,and most of them are in the form of Fe³⁺.After the right amount of Fe entered the lattice of TiO₂,it replaced the position of Ti.And the Fe-TiO₂ photocatalysts inhibited the growth and reagglomeration of grain effectively,introduced oxygen vacancy,reduced the band gap value,and improved the absorption performance of visible light.The effects of preparation temperature and Fe doping concentration on photocatalytic degradation of MB were investigated.When the preparation temperature was 240°C and Fe doping concentration was 1%,Fe-TiO₂ material obtained the strongest photocatalytic activity,and the reaction rate constant was 2.5 times of undoped brown TiO₂ and 3.5 times of P25.?2?The preparation of B-TiO₂ nanomaterials and their photocatalytic degradation performanceNano TiO₂ were modified by doping non-metallic ion with boric acid as source of boron,and the B-TiO₂ brown nano photocatalysts with visible light absorption,small grain size?5.7⁶.0 nm?and high specific surface area(217²29 m²?g^-1)were synthesized by one-step modified sol-gel method at low temperature.The results showed that the doped B should be in an interstitial position of TiO₂ in the form of Ti-O-B.Because the 2p orbit of interstitial B³⁺overlaped with the 2p orbit of O^2-,the band gap was reduced,the scope of light absorption was broadened.The effects of B doping concentration on photocatalytic degradation of MB were investigated.when B doping concentration was 15%,B-TiO₂ material obtained the strongest photocatalytic activity,and the reaction rate constant was 5.3 times of undoped brown TiO₂ and 7.3 times of P25.?3?The preparation of graphene-TiO₂ nanocomposites and their photocatalytic hydrogen production performance.Nano TiO₂ were modified by compositing with graphene with cetyltrimethyl ammonium bromid?CTAB?as source of carbon,and the graphene-TiO₂ brown nano photocatalysts with visible light absorption and small grain size?5.2⁶.1 nm?were synthesized by one-step modified so-gel method at low temperature.CTAB was used as a carbon source to form graphene structure during the preparation process,and also to prevent grain agglomeration.Characterization and analysis proved that CTAB molecules had been basically eliminated when the temperature was 240°C and above,and the formed graphene was 4⁵ layers.Photocatalytic hydrogen production under visible light of the graphene-TiO₂samples were tested,in order to determine the optimal amount of graphene composite.At that time,the amount of CTAB were 0.2g with about 6.21%mass fraction of graphene by TGA and DSC analysis speculation.And the hydrogen production quantity under visible light of graphene-TiO₂ was more than four times of unmodified brown TiO₂ after 6h.