| The preparation of high-efficiency and low-cost photocatalyst is the essential method to promote the development and practical application of photocatalytic technology.Titanium dioxide,with non-toxicity,low cost,good photocatalytic activity and high stability,is considered as one of the best photocatalytic materials for solving environmental problems.However,it suffers from several weakness such as the poor absorption of visible light,easily recombined photo-generated carriers,which limits its practical application.In order to solve the mentioned problems,tetrabutyl titanate?TBOT?and hydrazine hydrate?N2H4·H2O?was used as the titanium source and the reducing agent to prepare Ti3+self-doped TiO2-x,respectively.In order to further improve photocatalytic performance,high energy?001?crystal surface was exposed by fluorination treatment,and g-C3N4/F-TiO2-x-x heterojunction was formed by complexing with g-C3N4.The mechanism of photocatalytic degradation of rhodamine B was revealed.The main contents and results of this paper are as follows:Ti3+self-doped TiO2-x photocatalytic material was prepared by hydrothermal method using tetrabutyl titanate?TBOT?as titanium source and hydrazine hydrate?N2H4·H2O?as reducing agent.When the hydrothermal temperature was 180?,the hydrothermal time was 24 h,and the volume ratio of TBOT to hydrazine hydrate was 5:1,the prepared material possessed the best photocatalytic degradation performance?with the band gap is 2.85 eV?.The presence of a certain amount of Ti3+or oxygen vacancies effectively extends the light absorption range of the material,what is more the introduction of a small amount of N element into the TiO2 lattice further promoted the absorption of visible light.In addition,a small amount of rutile TiO2 is advantageous for improving the separation efficiency of photogenerated electron holes.Compared with commercial P25,the degradation performance is improved by about 4.6 times.In order to improve the stability of Ti3+or oxygen vacancies and further improve the performance of the catalytic material,a certain amount of HF was added to the preparation process of TiO2-x for fluorination treatment to prepare F-TiO2-x photocatalyst.When the dosage of HF was 0.3mL,the prepared material possessed the best photocatalytic degradation performance?with the band gap is 2.82 eV?.HRTEM showed that the high energy surface?001?was exposed after fluorination treatment.Moreover,the stability of the fluorinated materials is significantly higher than that of TiO2-x,indicating that fluorination is beneficial to the formation and stabilization of Ti3+and oxygen vacancies.Moreover,compared with TiO2-x degradation of three organic dyes?RhB,MO,MB?,the degradation rate was increased by 1.27 times,1.15 times and 1.25 times,respectively.In order to further improve the separation efficiency of photogenerated electrons and holes,F-TiO2-x and g-C3N4 were combined by hydrothermal method to form a composite photocatalyst.When the mass fraction of g-C3N4 was 25%,the prepared material possessed the best photocatalytic degradation performance.The photocurrent density of 25%C3N4/F-TiO2-x was 0.0037mA/cm2,and it was 7.8 times higher than that of commercial P25,3.9 times higher than that of F-TiO2-x and 3.3 times higher than that of g-C3N4,which indicates that the separation efficiency of photogenerated electron hole pairs was greatly improved.Compared with F-TiO2-x,the degradation rate of three organic dyes?RhB,MO,MB?was increased by 2.1 times,1.8 times and 1.5 times,respectively.Active species analysis showed that the most active species was·O2-in the process of photocatalytic degradation of rhodamine B by g-C3N4/F-TiO2-x. |
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