Preparation And Characterization Of TiO₂ And K₂Ti₆O₁₃ Nanowires

TiO₂and K₂Ti₆O₁₃ are two representative Ti-O based multifunctional semiconductor nanomaterials.Due to their huge aspect ratio and excellent physical and chemical properties,the one-dimensional nanowires of the two have been successfully and widely used in the fields of photo-catalysis,photolysis of water and energy,in order to solve the problems of environmental pollution and energy shortage faced by mankind at present.At present,the research on these two materials is mainly focused on controlled preparation and doping modification.For both the controllable preparation of nanowire,the preparation methods of titanium dioxide nanowire mainly concentrated in the hydrothermal method and vapor deposition method,but inevitably found throughout all of its preparation is the expensive and toxic precursor mostly used isopropyl alcohol titanium,tetra-butyl titanate,titanium tetrachloride and other organic metal and metal salts.In addition,the preparation of TiO₂ nanowires by vapor deposition method is also faced with the tedious and time-consuming step of depositing a layer of expensive metal film as catalyst through magnetron sputtering and atomic layer deposition in advance.For K₂Ti₆O₁₃nanowires,it is mainly prepared by solid phase sintering and co-solvent method.The biggest problem it faces is high temperature and the addition of excessive co-solvent,and the structure morphology and size uniformity of the obtained nanowires have been poor.In addition to the above controllable preparation,it is found that these two materials are faced with the problems of low light utilization and easy recombination of photo-generated carriers due to the wide band gap of TiO₂(3.0-3.2e V)and K₂Ti₆O₁₃(3.42e V)in the practical application process,so they must be doped and modified.Among all the modification strategies,graphene is considered to be a material that can significantly improve the photochemical properties of TiO₂ due to its high electron mobility,while g-C₃N₄(2.7e V)can effectively build a heterojunction with K₂Ti₆O₁₃ due to its appropriate band gap width,thus enhancing its photochemical properties.In view of the above questions,we adopt the method of simple and easy to get cheap containing titanium precursor for the preparation of nanowires,and systematically studies the parameters to affect the structure and morphology of the nanowires,then two kinds of materials respectively with graphene and g-C₃N₄composite were modified,and the light catalytic degradation of organic dyes,characterization of its photocatalytic performance.The main research contents and results of this paper are as follows:TiO₂ nanowires were prepared on Si O₂ substrate by mixing-embedding-calcining method,using metal Ti powder as precursor,adding a small amount of KF as catalyst,adjusting the experimental parameters and scheme.It was found that a layer of polycrystalline titanium film could grow after holding at 750?for 15 min with 1.5%KF.Then we further extended the holding time to 60 min,and finally took it out and thermal oxidation it at 660?for 90 min to get the rutile titanium dioxide nanowires.By combining the hydrothermal method with the calcination method,TiO₂nanowire powder was prepared by adding different concentrations of Na OH solution at different temperatures and holding time,and then the nanowire products were pickled and annealed at different temperatures.Finally,nanowires with diameters of100-200 nm and lengths of 40-50?m were obtained by reacting at 200?for 24h in9M Na OH solution.Then,anatase TiO₂ nanowires were obtained after 8 times of cleaning with 0.1M dilute hydrochloric acid and annealing at 850?for 2h.During the growth of composite graphene on titanium dioxide nanowires by different methods,the first successful 200sccm acetone vapor as carbon source,without hydrogenation and catalyst,growing at 850?for 100min to prepare multilayer graphene structure.Using improved sintering method,KF as potassium source and co-solvent,TiO₂powder as titanium source,by adjusting the amount of KF,reaction temperature,reaction atmosphere and heating rate and other parameters,finally in the amount of45%KF,800?,ethanol atmosphere reaction for 90 minutes,to prepare uniform size,diameter of about 100nm.Carbon doped K₂Ti₆O₁₃ nanowires with length of 40?50?m.K₂Ti₆O₁₃/g-C₃N₄ hetero-composites were prepared by different methods and their photocatalytic degradation of MB was studied.Finally,K₂Ti₆O₁₃ composites with different g-C₃N₄ additives were successfully prepared by direct mixing method.The reaction rate constant of K₂Ti₆O₁₃ and 12%g-C₃N₄ was the highest,and the methylene blue was 100%degraded after 2h irradiation under simulated sunlight.