Preparation And Application Of Black Mesoporous TiO 2 /SiO 2 /gC 3 N 4 Visible Light Photocatalyst

With the progress of society and the development of economy,environmental pollution and energy shortage are becoming more and more serious.Photocatalytic technology has gradually become an important way to solve environmental problems and ease the energy crisis.Among multitudinous photocatalytic materials,titanium dioxide?TiO₂?has aroused interest of researchers due to the nontoxicity,high chemical stability,and superior photocatalytic activity.However,the disadvantages of titanium dioxide also seriously affect its practical application.For example,the wide band gap only absorbs ultraviolet light and the high recombination rate of photogenerated charges and holes decrease the utilization of electrons and holes.In order to effectively solve the above problems,carbon nitride?g-C3N4?material with a narrow band gap is introduced,which can be successfully combined with titanium dioxide?TiO₂?.The formed heterojunction structure can accelerate the separation efficiency of electrons and holes.In order to further extend the response range of materials to light,Ti³⁺is successfully introduced into the system.The addition of Ti³⁺can significantly reduce the conduction band position,shorten the forbidden band width and broaden the absorption range of light.In recent years,mesoporous materials have become a research hotspot in the scientific community because mesoporous materials with a large specific surface area can enhance the adsorption of pollutants.In this paper,black mesoporous TiO₂/SiO₂ and black mesoporous TiO₂/SiO₂/g-C₃N₄ composite photocatalysts were prepared.The prepared samples were characterized by XRD,FT-IR,XPS,N₂ physics adsorption-desorption,UV-vis,SEM and TEM.Methyl orange and phenol were used as the target pollutants for photocatalytic degradation.At the same time,the hydrogen production performance of composite photocatalyst was also explored.The research results include:?1?The black mesoporous TiO₂/SiO₂ catalysts were successfully synthesized by hydrothermal and high temperature hydrogenation using butyl titanate and orthosilicic acid as precursors.The best calcining condition is continuous calcination for 2 hours at200?,followed by calcination at 350?for 2 hours and calcination at 450?for 4hours.The synthesized catalysts showed excellent photocatalytic activity.The degradation efficiency of methyl orange and phenol were 92.0%and 83.4%,respectively,and the efficiency of photocatalytic hydrogen production was 182.62?mol h^-1 g^-1.?2?The black mesoporous Ti O₂/SiO₂/g-C₃N₄ catalysts were prepared by sol-gel and high temperature hydrogenation reduction method,and the best mass ratio of mesoporous TiO₂/SiO₂ and g-C₃N₄ was 4:1.The characterization of the test showed that the mesoporous TiO2/SiO2 with mesoporous structure was uniformly covered on the g-C3N4 surface with lamellar structure,and the heterojunction structure could promote the separation of photogenerated electron and hole pairs.At the same time,the mesoporous structure with large specific surface area could enhance the adsorption of pollutants.In addition,the addition of Ti³⁺could extend the range of response to light and enhance the absorption of visible light.Therefore,the black mesoporous TiO₂/SiO₂/g-C₃N₄ exhibited the best photocatalytic activity under visible light irradiation.The degradation efficiency of methyl orange and phenol were 98.0%and98.5%,respectively,and the hydrogen production efficiency was 572.6?mol h^-1 g^-1.