Construction And Performances Of Inorganic Aerogel Photocatalyst

With the continuous progress of science and technology and the rapid development of industry,while humans enjoy convenient living,they are also facing increasingly serious environmental pollution and energy shortage.Photocatalysis,as a green,economical,and efficient technology,is considered as an ideal strategy to cope with environmental pollution and energy crisis.Aerogel is a three-dimensional porous material with special properties,such as high porosity,low density,and huge specific surface area.Therefore,it has become a novel and effective way to improve the photocatalytic activity by immobilizing photocatalysts onto aerogels,which is a research topic with application prospect and practical value.The main research content in this thesis is as follows:1.TiO₂/C/BiOBr graphene aerogel was prepared by a combination of an electrostatic spinning with a solvothermal method.The results show that the prepared aerogel has three-dimensional porous structure,and the optimized sample 2TCBA-II achieves a degradation rate of 97.5%for Rh B within 100 minutes under simulated sunlight irradiation,which is about 8.7 times better than pure TiO₂/C.It also has a high degradation rate for other organic pollutants（methyl orange,methyl violet,ciprofloxacin,and tetracycline hydrochloride）.In addition,TiO₂/C/BiOBr graphene aerogel has convenient recycling and good recyclability.The excellent performance is mainly attributed to the formation of heterojunctions between TiO₂and BiOBr,which reduces the recombination of photogenerated electron-hole pairs,and the surface sensitization of carbon nanofiber and graphene enhances the light absorption,as well as the large specific surface area in aerogel provides more active site.2.The g-C₃N₄/TiO₂/ZnIn₂S₄graphene aerogel（CTZA）photocatalyst material with a double Z-scheme heterogeneous structure was prepared by isoelectric point assisted calcination using graphene aerogel as a carrier.Under simulated sunlight irradiation,through the synergistic effect of photocatalysis and adsorption,the reduction rate of Cr（VI）by CTZA composites reaches 98.3%within 70 min,and the degradation efficiency of MO reaches 97.5%within 30 min.The charge transfer mechanism of the double Z-scheme heterostructure in the CTZA photocatalytic system is proposed and confirmed via the combination of the DFT theoretical calculations with a series of experiments.In addition,the CTZA photocatalyst exhibits a high hydrogen evolution rate(6531.9μmol g^-1).The excellent photocatalytic performance of CTZA is mainly due to the advantages of both heterojunction photocatalyst and graphene aerogel framework.The formation of double Z-scheme heterostructure can more effectively promote the separation of photogenerated electron-holes and improve the reduction and oxidation ability.The graphene aerogel skeleton not only provides more active sites,but also the unique three-dimensional network provides abundant electron transport channels,which accelerates the transport rate of carriers.3.The ZnIn₂S₄nanosheets with S vacancies（S-ZISA）were in situ grown on graphene aerogels by a facile one-pot oil bath method.The construction of S vacancy can enhance light absorption by modulating the electron band structure and become an effective electron capture active site.Under visible light irradiation,via the synergistic effect of adsorption and photocatalysis,the optimized sample S-ZISA-2 achieves 98%reduction rate of photo-reduced Cr（VI）in 60 min,and with a rate constant(0.054 min^-1)that 4.5 times higher than that of ZnIn₂S₄(0.012 min^-1).The cycling experiments show that S-ZISA-2 has good cyclability,and the effects of p H value and coexisting anions in solution on the photo-reduction of Cr（VI）have been investigated.In addition,the S-ZISA-2 photocatalyst also exhibits a high hydrogen evolution rate(2011.7μmol g^-1).ZnIn₂S₄nanosheets can form Schottky junctions with graphene,which effectively accelerates the migration of photogenerated carriers and hinders the carrier recombination,thereby enhancing the photocatalytic activity.The three constructed composite aerogel photocatalysts have good photocatalytic efficiency,which is mainly attributed to the synergistic effects of high specific surface area,excellent electron migration rate and formation of heterojunctions in the composite aerogel photocatalysts.The new results obtained provide new ideas for the development of other efficient photocatalysts.