The Photoelectric Conversion And Photocatalytic Performance Of Nano TiO₂ With Special Morphologies

Energy shortage and environmental pollution are two major issues which can't be ignored in today's society.They are also two big problems that related to the sustainable development of our human society.As we all know,the development and utilization of new energy is the hope of alleviating the shortage of resources and controlling the environmental pollution.Solar energy is the one which has unique advantages and great potential for development among many new energy sources.The solar energy can be converted into electrical energy by solar cells and photocatalysis can be used to convert solar energy into chemical energy.As one kind of wide band gap semiconductor material,TiO₂ has been widely used in the fields above and plays an important role in the process of improving the environment and alleviating the lack of resources.In this paper,TiO₂ nanocrystals with various morphologies were prepared by hydrothermal method,and then the samples were applied into the dye sensitized solar cell and photocatalytic degradation of organic dye.We are trying to give the working principle and possible direction of high efficiency photoanode and photocatalyst through different experiment.Four sections are contained as follows:?1?Firstly,perovskite SrTiO₃ particles were synthesized by hydrothermal method which was firmly attached onto the surface of FTO by a scraping method.Subsequently,titanium oxysulfate and the SrTiO₃ thin film was used as the titanium source and substrate.The bilayer TiO₂ thin films was synthesis by hydrothermal method.Structural characterizations reveal that Ti O₂ comprises of two phases: anatase film at the bottom and single-crystal rutile nanorods grown along the [110] direction on top.The TiO₂ nanorods are integrated into the flower shape and are distributed on the SrTiO₃ substrate evenly.In comparison with pure TiO₂ and SrTiO3,the composite photoanode shows a much better performance in photoelectric conversion efficiency?1.35 %?,which is about 2 and 100 times as efficient as pure TiO₂ and SrTiO3,respectively.Considering the morphology and structure of the anode,it can be known that,SrTiO₃ plays an important role in the reduction of electron-hole recombination.First,the existence of SrTiO₃ facilitates the charge carrier transfer on the interface of TiO₂ and SrTiO3.At the same time,it changes the morphology and structure of TiO₂,which also reduce the electron-hole recombination and improve the photoelectric conversion efficiency of the solar cell greatly.?2?The TiO₂ nanoparticles with good crystallinity were obtained by adding different amounts of ammonia in the hydrothermal preparation process.The SEM images show that the overall size of the nanoparticles did not change with the increase of the amount of ammonia.But the size of the small nanoparticles is obviously increased.With the increase size of the small grains,the BET surface area of the samples decreased sharply.Then the obtained products were applied to the photocatalytic degradation and dye sensitized solar cells to measure the photochemical conversion and photoelectric conversion ability.In the photocatalytic process,because the BET surface area of the samples was decreased with the increase of the amount of ammonia,the photocatalytic degradation of the sample decreased;while in the dye sensitized solar cells,the photoelectric conversion efficiency increases first and then decreases.The reason is that,with the increase of the concentration of ammonia,the crystallinity of TiO₂ nanoparticles increased,but the specific surface area of the samples decreased insignificantly.The two influences on solar cell photoelectric conversion capability is the opposite and a ? of 5.58% is obtained at the end.Using a non-calcination method to improve crystallinity and finally improve the efficiency of electronic transmission without changing the crystal phase and morphology of TiO₂ is a very enlightening method.?3?TiO₂ nanoparticles with large specific surface area were synthesized by a two-step hydrolysis-hydrothermal method,using titanium tetraisopropoxide as the titanium source.The effect of calcination temperature on the properties of TiO₂ was discussed.Using reactive brilliant red dye X3 B as substrate and TiO₂ as the photocatalyst,the photocatalytic degradation were carried out under the acidic condition.The sample has excellent photocatalytic degradation effect on dye X3 B.It shows that,with the gradually increase of the calcined temperature,the photocatalytic performance decreased significantly.It is consistent with the variation of BET surface area.It is proved that the catalytic reaction is an interfacial catalytic reaction.Uncalcined sample shows the best catalytic activity,the decolorization rate of dye can reach 52% in 10 minutes,and the dye solution is completely decolorized degradation in 20 minutes.In addition,the photocatalytic activity of the as-prepared TiO₂ is much higher than that of commercial P25,and it shows a great value in the application of photocatalytic degradation of dye wastewater.?4?The Fe₃O₄ loaded TiO₂ photocatalyst with different mass ratio were successfully synthesized by a convenient calcining method,using the ironic oxalate as the iron source.It was confirmed by XRD patterns that the anatase phase of TiO₂ and the magnetite phase of Fe₃O₄ were obtained.The morphology analysis by SEM and TEM suggested that the Fe₃O₄ are very fine-grained particles which couldn't be detected easily.In the photocatalytic experiment,the 200:1 TiO₂-Fe sample exhibits more excellent photocatalytic activity than that of blank TiO₂.The immobilized iron shows similar activity with free Fe3+ with the existence of H2O₂.But the TiO₂ 200:1 sample shows extremely stable photocatalytic activity in cycling experiment.And the sample with magnetic property is easy for recycling.The content of iron in the sample is unchanged in the reaction process after immobilization which will not cause second pollution to water by iron mud.All above advantages indicated the great potential of the photocatalyst for practical application.