Construction Of TiO₂ Based Heterostructures And Photocatalytic Properties Research

As a safe,cheap,stable and widely applied photocatalyst,titanium dioxide（TiO₂）with high research and application values in photocatalystic and photoelectric energy conversion yields.In this work,based on the crystal structure and intrinsic properties of TiO₂,various TiO₂ based heterostructures were synthesized by the routes such as expanding the light absorption range.The formation processes of heterostructure were studied.Relationship between component,morphology and energy band structure of the samples were also analyzed.Specific works are as follows:1.The construction of TiO₂（B）/g-C₃N₄ layered heterojunctions was finished by expending the photo-adsorption in visible light region.The heterostructure revealed powerful photoresponse under full spectrum and visible light irradiation.With the increase of TiO₂,photocatalytic performance of the sample increased firstly and then decreased.The mixed phase ultra-thin TiO₂ nanosheets composed of TiO₂（B）and anatase provided abundant active sites;Interface between the two components could prevent the rapid recombination of photogenerated carriers;Unique 2D/2D g-C₃N₄/TiO₂ composite interface improved the migration efficiency of photogenerated carriers,thereby enhanced the photocatalytic reaction ability.With the complementarity of these two components in the light absorption region,the photocatalytic performance of the sample was significantly improved.The photoreduction rate of Cr（Ⅵ）under full spectrum was triple higher than that of pure TiO₂,and the degradation rate of antibiotics under visible light was twice higher than that of g-C₃N₄.2.WO_3-x was loaded to enhance visible-near infrared light absorption of TiO₂.Non-stoichiometric WO_3-x nanoparticles were loaded on surfaces of 3D nanostructure assembled by ultra-thin TiO₂ nanosheets.Light response of the sample in the visible-near infrared region was clearly enhanced.After loading 10%WO_3-x,the photocatalytic removal rate of the sample to MO and Cr（Ⅵ）reached five and seven times than those of pure TiO₂nanosheet,respectively.There are two main factors for the remarkable improvement of photocatalytic performance.First,thickness of TiO₂ nanosheets is not more than 5 nm,which improves the light transmittance and enhances the productivity of photogenerated carriers when the sample is illuminated.On the other hand,reaction efficiency is improved bythe abundant surface oxygen vacancies as reactive sites,which also improves the light absorption and photogenerated carrier yield of the samples,and effectively prevents the recombination of photogenerated electrons and holes.In addition,the loading of WO_3-x nanoparticles enables the material to absorb near-infrared light and visible light.And heterostructure makes the charge transfer between WO_3-x and TiO₂ to be realized,thereby improving the optical quantum efficiency of the sample.3.Construction of TiO₂/Co-Al LDH heterojunctions improved absorption property and charge transport efficiency of the material.After loading Co-Al LDH on surfaces of 1D mixed phase TiO₂ nanobelts,conductivity of the samples was improved,and photogenerated carrier migration rate increased much.The sample showed excellent performance of adsorption-photoreduction double mechanism for Cr（Ⅵ）removal,and the samples prepared by using TiO₂ nanobelts calcined at 400 ℃ with the best Cr（Ⅵ）removal efficiency.Photocatalytic performance improvement is attributed to the large surface area of mixed phase TiO₂ nanobelts,which provides abundant surface active sites.Photogenerated carriers migrate across between anatase and TiO₂（B）,which improves the separation efficiency.Introductionof Co-Al LDH further enlarged specific surface area of the sample and enhanced absorption property for Cr（Ⅵ）.Conductivity of the sample was also improved,which obviously quickened the photogenerated carrier migration rate.4.Using excellent photocatalytic property of TiO₂ and good gas sensing property of SnO₂,two composites were synthesized for photocatalytic and gas sensing fields,respectively.First,amorphous SnO₂ nanoparticles were loaded on the surface of anatase TiO₂ nanoflowers exposed（001）facets.The photocatalytic property of obtained sample enhanced much.The two crystals with similar structure,SnO₂ can store electrons generated by TiO₂ and promote the separation of photogenerated carriers.The photocatalytic degradation and photoreduction rates of heterostructures are 3 times higher than those of pure TiO₂.In another experiment,amorphous SnO₂ nanoparticles were loaded on surfaces of TiO₂（B）nanospheets by a similar method.The sample with good sensitivity to organic volatile gas,and the selectivity to target gas was improved,too.The unique structure with evenly distributed SnO₂ nanoparticles.And TiO₂（B）could provide electrons for gas sensing process.So,the formation of SnO₂/TiO₂heterostructures plays an important role in performancesof deteceingvolatile gases.