Study On The Preparation And Photocatalytic Performance Of Noble Metal Loaded Hollow TiO₂

Titanium oxide（TiO₂）is currently the most studied semiconductor photocatalyst material with the advantages of environmental friendliness and high catalytic activity.However,TiO₂ semiconductor as a photocatalyst has a wide band gap energy of about 3.2e V,which can only respond to ultraviolet light atλ<387 nm.In this paper,the structure of TiO₂ is first modified to prepare TiO₂ with a hollow structure,and then the noble metals Au and Pd are loaded to modify it to improve its quantum efficiency and broaden its light response range,thereby effectively using sunlight.The modified catalysts are used to degrade organic pollutants in water and atmospheric environment to explore the improvement of photocatalytic performance of materials compared to pure TiO₂.At the same time,the physicochemical characteristics of the modified catalysts are investigated,and the mechanism of improving the photocatalytic effect is revealed.The primary research contents and results are as follows:（1）Solid spherical TiO₂ is prepared by hydrothermal method,meanwhile hollow TiO₂（denoted as TiO₂-H）is prepared by carbon sphere as template.TiO₂-H has obvious cavity and thin TiO₂ layer.The structure modification does not change the crystal structure of the material.TiO₂-H has a large specific surface area,which can provide more active sites for the reaction.Thin TiO₂ layer is also beneficial to the separation of photogenerated electrons and holes.Within 2 hours,TiO₂-H could degrade all 4-CP,with a degradation efficiency 35%higher than that of solid TiO₂,and a reaction kinetics constant 3.3 times higher than that of solid TiO₂.（2）In the process of preparing the carbon template,HAu Cl4 is added as the precursor of Au to prepare yolk-shell Au@TiO₂（denoted as Au@TiO₂-YS）.At the same time,Au nanoparticles are prepared by seed growth method to prepare solid core-shell Au@TiO₂（denoted as Au@TiO₂-CS）.Due to the LSPR effect of noble metals,the absorption range of Au@TiO₂ is extended to visible light area,and the utilization of light is improved.When the Au load was 0.14at%,both Au@TiO₂-YS and Au@TiO₂-CS catalysts show the best photocatalytic degradation efficiency.Au@TiO₂-YS provides a larger specific surface area and greater photogenic electron hole separation efficiency.The degradation efficiency of gaseous toluene by Au@TiO₂-YS under visible light（λ>400 nm）can reach 57%within3 h,which is 22%higher than that of Au@TiO₂-CS.In addition,cyclic degradation experiments show that the two catalysts have good stability.（3）Gold palladium（AuPd）alloy is prepared by the method of NaBH4 reduction,and yolk-shell Au Pd@TiO₂（denoted as Au Pd@TiO₂-YS）is prepared by the template method.Au Pd alloy is used as the core and TiO₂ is used as the shell.Au Pd@TiO₂-YS has a large specific surface area and mesoporous pores,which is conducive to gas exchange and reaction.Due to the synergism of double noble metals,Au Pd@TiO₂-YS has a wide spectral response performance,and the optical response range is further extended to the visible region and the near-infrared region,and the photocatalytic performance is significantly improved again.When the mole ratio of Au to Pd is 3:1,Au Pd@TiO₂-YS has the best photocatalytic degradation efficiency of o-DCB in gaseous phase under visible light（λ=420 nm）.Within 3 h,the degradation efficiency of Au Pd@TiO₂-YS on gaseous o-DCB is up to 75%,and the mineralization degree reaches 73%.Gaseous toluene is almost completely degraded and the mineralization degree reaches 93%.In addition,the catalyst still has high photocatalytic degradation effect on the two volatile organic compounds（VOCs）coexistence system.Both o-DCB and toluene have high mineralization degree in gas phase,and the catalyst remaine stable after three cycles of degradation.