Construction And Photocatalytic Properties Of SnO₂ And SiO₂ Matrix Composites

In this thesis,the disordered porous g-C₃N₄/SiO₂/SnO₂ composites were prepared by sol-gel method.Under the irradiation of visible light,the photocatalytic degradation characters of the prepared materials to the dyestuff type organic pollution of the composite was the best when the doped amount of g-C₃N₄ was 30 wt%.The composite had the much better photocatalytic degradation effects to methyl orange（MO）,methylene blue（MB）and rhodamine B（RhB）under the visible light.The photocatalytic degradation rates of the prepared materials to MB and MO were 99.73%and 95.58%after visible light irradiation for50 min,respectively.The photocatalytic degradation rate of the composite to RhB was95.10%after visible light irradiation for 90 min.This three dyestuff type organic pollutants of MB,MO and RhB were degraded 6 times respectively,and the degradation rates were retained above 90%,which indicated that the composite had the better reusability,and had environmental purification potential.In₂O₃ doped disordered porous amorphous In₂O₃/SnO₂ composite was prepared by sol-gel method combined with hard template method.In₂O₃ sensitized SnO₂ in prepared material.A large number of defects were generated in the porous SnO₂ matrix during the preparation process,the more photogenerated electrons were generated when the SnO₂ was irradiated by light with appropriate energy,and changed the transfer direction of the photogenerated electrons on the valence band of the SnO₂ matrix,which made the SnO₂matrix show the light absorption in visible light range.At the same time,a Z-type energy level structure was formed at the contact interface between In₂O₃ and SnO₂,which promoted the separation of electron-holes,and improved the photocatalytic degradation effect of the composite.When the doped amount of In₂O₃ was 1.5 wt%,the photocatalytic degradation effect of the composite to RhB was the best.After 100 min of visible light irradiation,the photo-catalytic degradation rate of the composite to RhB solution was reached 93.50%.After5 time cycles,the photocatalytic degradation rate was retained above 90%.The ordered porous amorphous CeO₂/SnO₂ composite was prepared by sol-gel method combinative hard template method.The SnO₂ was tetragonal phase structure in the composite.Undoped SnO2 matrix was composed of asymmetrical spherical particles stacked into a gel-like structure,the single particle average size was about 60-100 nm.The CeO2/SnO2（1.0 wt%Ce）composite material sample was a loose gel block structure which was formed by the small uneven spherical particles,and the small particles were connected to each other to form a analogous honeycomb morphology.The nitrogen adsorption-desorption test results showed that the specific surface areas of disordered porous SnO₂ matrix sample and CeO₂/SnO₂（1.0 wt%Ce）composite sample were 89.49 m²/g and356.14 m²/g,it indicated that the doped CeO₂ had a sensitization to the SnO₂ matrix,which made the crystal grains refinement of the prepared composite material,increased the specific surface area of the composite material,and increased the density of the reactive sites.Under visible light irradiation,when the doped amount of CeO2 was 1.0 wt%,the photohydrolysis of hydrogen production character of the composite was the strongest.After collecting hydrogen for 3.5 h,hydrogen production of SnO₂ matrix and CeO₂/SnO₂（0.5 wt%,1.0wt%,1.5 wt%,2.0 wt%Ce）composite samples were 698.9μmol,1146.0μmol,2193.7μmol,1368.3μmol and 931.0μmol,respectively.The average hydrogen production rate of CeO₂/SnO₂（1.0 wt%Ce）composite sample was 6267.7μmol/（g·h）,which was 3.14 times of the average hydrogen production rate of undoped SnO₂ matrix sample（1996.8μmol/（g·h））.The g-C₃N₄/SiO₂ composite was prepared by sol-gel method.When the doped amount of g-C₃N₄ was 50 wt%,photocatalytic degradation performance of the composite to RhB was the best.The g-C₃N₄/SiO₂（50 wt%g-C₃N₄）composite sample exhibited a loose porous structure.After 90 min of visible light irradiation,the degradation rate of the prepared material to RhB reached 96.42%.After 5 time cycles experiment,the photocatalytic degradation rate was retained above 90%,which indicated that the composite had the much better cycle stability.