Modification Of TiO₂ Nanomaterials And Their Photocatalytic Properties

Energy and the environment are the two major issues of concern to the world today.As an advanced and non-polluting process,photocatalytic technology has proven to be very effective in the field of environmental remediation and energy conversion.Photocatalytic technology can be carried out in the absence of toxic and non-corrosive agents compared to conventional chemical methods.Recently,it has been reported that a semiconductor photocatalyst is applied to an oxidation/reduction process,for example,benzyl alcohol can be selectively oxidized to benzaldehyde,or CO₂can be reduced to a hydrocarbon fuel such as CO or CH₄.In this thesis,TiO₂semiconductor is the research object,but Ti O₂belongs to the wide band gap(3.2 e V)semiconductor material,which can only absorb the ultraviolet light,the low utilization rate of sunlight,the lower mobility of photogenerated electrons and holes and shorter photo-carrier lifetime limits its application.Therefore,in this paper,we have modified some Ti O₂and studied its photocatalytic performance.The main research contents and results are as follows:(1)2D-2D SnS₂/TiO₂nanocomposites were synthesized by two-step hydrothermal method.A series of Sn S₂/P25 samples were also prepared to compare the superiority of the Sn S₂/Ti O₂nanosheet structure.The samples were characterized by XPS,PL,TEM,SEM and UV-Vis DRS.The photocatalytic reduction of CO₂was selected as the basis for the evaluation.The photocatalytic activity of 2D-2D Sn S₂/Ti O₂composites under simulated sunlight was investigated.When 2D-2D Sn S₂(5%)/Ti O₂was used as the photocatalyst,the yield of CH₄was up to 23?mol/g,which was 20 times higher than that of P25.(2)Nitrogen vacancy g-C₃N₄(CNNA)was obtained by adding nitric acid treatment during the preparation of conventional g-C₃N₄.Ti O₂was prepared by precipitation method,Ti O₂was treated with a small amount of H₂O₂ice water bath,and CNNA-OTi O₂amorphous composite structure was obtained by adding CNNA.The materials were characterized by XRD,SEM,TEM,UV-Vis DRS,FT-IR and so on.The photocatalytic reduction of CO₂was selected as the basis for evaluation.Under visible light,CNNA-OTi O₂composites exhibited excellent photocatalytic activity.When visible light was irradiated to CNNA(10%)-OTiO₂composite for 1 h,the rate of CH₄production reached 23.2?mol/g.(3)By high temperature modification of TiO₂with H₂O₂,excess oxygen-deficient titanium dioxide(O₂-Ti O₂)is formed to produce a peroxy group.Secondly,nickel ions are doped in O₂-Ti O₂to form a Ni-OTi O₂composite.The samples were characterized by XPS,FT-IR,UV-Vis DRS,XRD and EIS.The photocatalytic oxidation of benzyl alcohol was selected as the basis for the evaluation.The photocatalytic activity of Ni-OTi O₂composite under visible light was investigated.When Ni(1%)-OTi O₂is used as a photocatalyst,the activity is the highest,and the conversion rate of benzyl alcohol reaches 86%.