Synthesis And Modification Of Single Crystal Titanium-based Photocatalysts By Molten Salt Method

Titanium-based photocatalyst possesses many advantages including non-toxicity,stability of physical and chemical properties,and low cost.As a highly efficient semiconductor photocatalyst,it has been widely used in the field of photocatalysis.However,the wide band gap and high electron hole recombination rate of titanium-based photocatalyst limit its broad application.In recent years,the improvement of the photocatalytic ability of titanium-based photocatalyst has become the focus of this field.Therefore,this thesis focuses on the improvement of the properties and preparation methods of titanium-based photocatalysts.In this dissertation,to prepare high-performance titanium-based photocatalyst is the main object of study.Titanate,N-doped?nitrogen doped?and?N,F?-codoped?nitrogen and fluorine codoped?TiO₂ were prepared by molten salt method with introducing nitrate during the process of calcination.The calcination temperature of the samples was reduced and the photocatalytic activity was improved by molten salt method.The effects of molten salt system on the structure,composition,band gap and photocatalytic mechanism of the samples were investigated.The composition,morphology,structure and optical properties of the samples were analyzed.The main results are as follows.?1?N-doped single crystal TiO₂ prepared by molten salt method had high photocatalytic degradation efficiency for MB under visible light irradiation.Nitrogen doping could reduce the band gap energy of Ti O₂ and improved the utilization of visible light.The molten salt system promoted the formation of single crystal TiO₂,the increase of specific surface area and the formation of NO species on the surface,which were beneficial to improve the photocatalytic ability of the sample.?2?The?N,F?-codoped crystalline TiO₂ prepared by molten salt method had high?001?surface exposure rate,which was beneficial to improve the photocatalytic performance.The nitrogen and fluorine codoped could reduce the band gap of TiO₂ and improved the utilization of visible light.In addition,NO and fluorine ions existed on the surface of Ti O₂ was beneficial to improve the photocatalytic performance.?3?With the increase of calcination temperature,the specific surface area of the titanate catalysts prepared by molten salt method decreased while the band gap increased first and then decreased.The band gap of the sample calcined at 600 oC was the minimum,while the band gap of the sample calcined at 700 oC was the maximum.The titanate nano-belt which had a layered structure was successfully prepared at 650 oC,and had better photocatalytic effect.