Construction And Performance Of Rare Earth Oxyselenide And Their Complexes Nanostructured Materials

Photocatalytic technology has broad application prospects in solving the problems of environmental pollution and energy shortage.However,there are still some problems in the photocatalytic process,such as easy recombination of photo-generated carriers,low photo-degradation efficiency and narrow light response range.Therefore,the development of new-typed photocatalysts with high photocatalytic efficiency and cost effectiveness is one of the current research hotspots.The band gap of rare earth oxyselenide is in the range of 1.4-2.0 e V,which can capture more light energy.However,due to the limitation of the preparation method,the research on this kind of materials in the field of photocatalysis is rarely reported.Therefore,study on the preparation and performances rare earth oxyselenide heterojunction photocatalysts becomes an important research topic.In this dissertation,three kinds of rare earth oxyselenide nanofiber heterojunction photocatalysts are prepared by electrospinning,double-crucible selenization technique,hydrothermal method and urea sublimation method.The structure,morphology and photocatalytic properties of the target samples are characterized by XRD,SEM,EDS,XPS,UV-Vis and PL.The details are as follows:1.A new-typed La₄O₄Se₃/CdS heterojunction one-dimensional nanofibers photocatalyst is prepared by combination of electrospinning,double-crucible selenization and hydrothermal method.Under simulated sunlight irradiation,the hydrogen production rate of the best photocatalyst is 6.47 mmol·h^-1·g^-1,and the photo-degradation rate of tetracycline hydrochloride（TCH）reaches 87.4%for 180 min illumination.Further,the photocatalyst has good cyclic stability.2.La₄O₄Se₃/g-C₃N₄ composite nanofibers heterojunction photocatalyst is successfully synthesized by a new technique of electrospinning combined with double-crucible selenization and urea sublimation method.The loading amount of g-C₃N₄ on the surface of one-dimensional La₄O₄Se₃ nanofibers can be controlled by adjusting the amount of urea added in the sublimation process.Under simulated sunlight irradiation,the photocatalytic hydrogen production efficiency of the best sample is 3.28 mmol·h^-1·g^-1,and the photo-degradation rate of TCH achieves 89.2%at the irradiation for 160 min.The photo-catalyst possesses eminent photocatalytic hydrogen evolution and degradation of antibiotics bi-function.3.La₂O₂Se nanofibers are synthesized by electrospinning combined with double-crucible selenization method,and then La₂O₂Se/CdS nanofibers heterojunction photocatalyst is prepared via hydrothermal method.When the CdS content is 10 wt%,the hydrogen production rate of the sample reaches 2.16 mmol·h^-1·g^-1,and the photo-degradation rate of TCH is 86.4%under simulated sunlight irradiation for 200 min.The three heterojunction photocatalysts prepared in this work all have excellent photocatalytic hydrogen evolution and degradation of antibiotics bi-functionality,which result from the joint effect of expanding the light response range of the samples and improving the efficiency of photo-generated electron-hole pairs separation.The new findings provide a new idea for the development of other novel rare earth oxyselenide heterojunction photocatalysts in the future.