Study On Photocatalytic Properties Of Metal@SiO₂ Enhanced Two-dimensional Materials

Organic pollutants are the key to solve environmental problems.Two-dimensional materials are commonly used as photocatalysts for photocatalytic degradation of pollutants.However,due to the wide band gap of two-dimensional materials and the high recombination rate of photogenerated electron-hole pairs,a single two-dimensional material has a low photocatalytic efficiency.Metal nanoparticles are widely used to improve the photocatalytic efficiency of two-dimensional materials due to their unique Surface plasmon resonance（SPR）effect.There are three kinds of strengthening systems for the composite system of metal nanoparticles and two-dimensional materials:（1）Photon enhancement（light capture）（2）direct electron transfer（DET）（3）Plasmon-induced resonance energy transfer（PIRET）.Direct electron transfer is common in metal-2D composite systems,and direct contact and spectral overlap between metal nanoparticles and 2D materials are the key factors controlling DET and PIRET processes,respectively.Based on PIRET principle,we designed and synthesized composite nanomaterials which were combined with two two-dimensional materials respectively.And study the respective PEC performance and influencing factors.The material designed in this thesis is a composite nanostructure with metal nanoparticles coated with Si O₂ shell layer,and then combined with two-dimensional material.Because of the existence of Si O₂ shell layer,metal nanoparticles will not be damaged by corrosion in the process of photocatalysis.In addition,the microstructure of the composites was characterized by TEM,UV-vis,SEM and XRD.This research is mainly divided into the following three parts:（1）Au NS,Au NR were prepared by seed induction method,Au NS@Ag,Au NR@Ag were prepared by ascorbic acid（AA）reduction method.The metal@Si O₂（metal=Au NS,Au NS@Ag,Au NR,Au NR@Ag）with different Si O₂thickness was prepared by the improved Stober method.（2）Mo S₂ is synthesized by hydrothermal method.The PEC properties of@Si O₂combined with Mo S₂ were studied.The results show that the photocurrent intensity of@Si O₂/Mo S₂increases first and then decreases with the increase of Si O₂ thickness,and the photocurrent intensity increases first and then changes with the ratio of@Si O₂ to Mo S2.The corresponding metal nanoparticles all have the best Si O2 shell thickness and ratio to Mo S₂.Au NS@Si O₂（15 nm）/Mo S₂（1:1）,Au NS@Ag@Si O₂（19nm）/Mo S₂（1:1）,Au NR@Si O₂（16 nm）/Mo S₂（3:1）,Au NR@Ag@Si O₂（26nm）/Mo S₂（3:1）.（3）The PEC properties of metal@Si O₂ combined with Reduced Graphene Oxide（RGO）were studied.The results show that the photocurrent intensity metal of@Si O₂/RGO increases first and then decreases with the increase of Si O₂ thickness.Moreover,for several metal nanoparticles,there is an optimal thickness of Si O₂,and the photocurrent intensity increases first and then changes with the ratio of metal@Si O₂to RGO.The corresponding metal nanoparticles have the best Si O₂ shell thickness and ratio to RGO:Au NS@Si O₂（15 nm）/RGO（1:1）,Au NS@Ag@Si O₂（19 nm）/RGO（1:1）,Au NR@Si O₂（16 nm）/RGO（3:1）,Au NR@Ag@Si O₂（26 nm）/RGO（3:1）.