Preparation And Photocatalytic Properties Of TiO₂ Aerogel Composites

Titanium dioxide(TiO₂)has become one of the most commonly used photocatalysts due to its non-toxic,low cost,high stability and good catalytic activity.However,the wide band gap(3.2 e V)of TiO₂ makes it only activated by ultraviolet light at the wavelength below 390 nm,which leads to low utilization of sunlight,fast recombination of photogenerated electron-hole pairs,easy deactivation,and slow charge migration rate,which seriously limits the application of TiO₂.The surface modification of TiO₂ by metal ion implantation,non-metal doping,heterostructure building,dye sensitization and conversion luminescence agent doping can expand its light absorption range and improve photocatalytic performance.Graphene composites have good photocatalytic properties.The construction of graphene layer materials with three-dimensional cross-linked structures such as hydrogels and aerogels has become s new research focus.In this study,TiO₂/graphene composite aerogels were prepared by sol-gel method and freeze drying,which effectively solved the problems of smaller TiO₂ nanoparticles,easy agglomeration,narrow light response range and high electron-hole pair recombination rate.The research contents include:(1)Using tannic acid(TA)as the reducing agent,graphene oxide(GO)prepared by the modified Hummers method and tetrabutyl titanate(C₁₆H₃₆O₄Ti)as raw materials,the sol-gel method was used to prepare the graphene hydrogel loaded with TiO₂nanoparticles at atmospheric pressure of 90?,then a light,porous and hydrophobic titania/graphene aerogel(TiO₂/GA)was obtained by freeze-drying.A series of TiO₂/GA aerogels containing different amounts of C₁₆H₃₆O₄Ti and TA were prepared.The amounts of C₁₆H₃₆O₄Ti were 0.1 g,0.2 g,0.3 g,0.4 g and the mass ratio of GO to TA was 2:1,1:1,1:2.Studies have shown that the feed ratio of TA,GO,and C₁₆H₃₆O₄Ti had a greater impact on the morphology of TiO₂/GA aerogels.TiO₂ nanoparticles in TiO₂/GA aerogels were uniformly anchored on the graphene sheet,with a BET specific surface area of 111 m²/g.TiO₂/GA aerogels had good photocatalytic degration performance for orange IV and other azo dyes,and were easy to be recycled and reused.Among them,the mass ratio of GO to TA is 1:1,and the amount of C₁₆H₃₆O₄Ti precursor is 0.2 g,the prepared TiO₂/GA exhibits the highest adsorption and photocatalytic performance,and the photocatalytic degradation rate of Orange IV can reach 76%.(2)In order to broaden the absorption range of TiO₂ to sunlight and improve the photocatalytic efficiency,a hererogeneous composite technology was adopted,using curcumin(Cur),tetrabutyl titante(C₁₆H₃₆O₄Ti),graphene oxide(GO)as raw materials,and ascorbic aid as a reducing agent and crosslinking agent.The curcumin-sensitized TiO₂/GA(Cur/TiO₂/GA)was prepared by sol-gel method.Cur/TiO₂/GA aerogels with different contents of Cur and C₁₆H₃₆O₄Ti were prepared,the content of Cur was 1%,3%,5%,7%of C₁₆H₃₆O₄Ti,the mass ratio of GO to Cur/TiO₂ was 1:1,1:2,1:3,1:4.XRD,SEM,FT-IR,RAMAN,BET,XPS and UV-vis were used to analyze the morphology and chemical properties of the materials,study the surface morphology,crystal phase structure,functional group and chemical bonding,specific surface area,constituent element state and light response range of the material influencing factors.Photocatalytic experimens were carried out to investigate the effects of catalyst types,p H,catalyst dosage,quencher and different anions on the photocatalytic degradation of Orange IV,and the photocatalytic mechanism of Cur/TiO₂/GA aerogel was analyzed,so as to provide a theoretical basis for further improving the photocatalytic efficiency.In composite materials,when the content of Cur is 5%of C₁₆H₃₆O₄Ti and the mass ratio of GO to Cur/TiO₂ is 1:2,the Cur/TiO₂/GA aerogel prepared shows the best AO4degradation effect.Under ultraviolet light,the phototcatalytic removal efficiency of AO4 can reach 84.5%,while the degradation rate under visible light is only 56.5%.It is confirmed that·O₂^-is the main active substance in photocatalytic degradation of organic pollutants by Cur/TiO₂/GA composite aerogels,and its photocatalytic efficiency is still up to 81.1%after the five cycles test.It has stable mechanical properties,high reuse efficiency and easy recycling.