Effect Of Facet Index On Photocatalytic Properties Of Au/ui O-66-nh₂ Composites

As a renewable energy source,hydrogen has the advantages of high combustion heat,clean combustion products and wide range of sources.It is an ideal substitute for fossil fuels.The use of photocatalytic decomposition of water to produce hydrogen can effectively convert solar energy into fuel,which is one of the feasible methods to solve energy crisis and environmental pollution.In this thesis,Ui O-66-NH2 was used as the main component,and Au nanoparticles with different indices of crystal facets were selected as the modifications,with which the corresponding Au/Ui O-66-NH2 composites were prepared.The effect of the morphology and structure of Au nanoparticles on the photocatalytic hydrogen produnction performance of the composites were explored.Eight types of Au nanoparticles were synthesized with different crystal facets and morphologies including amorphous sphere（S-type）,planar triangle with{111}crystal facets（T-type）,cube with{100}crystal facets（C-type）,octahedron with{111}crystal facets（O-type）,rhombic dodecahedron with{110}crystal facets（RD-type）,tetrahexahedron with{520}crystal facets（THH-type）,trisoctahedron with{221}crystal facets（TOH-type）and hexoctahedron with{421}crystal facets（HOH-type）.All as-prepared Au nanoparticles were characterized by XRD,UV-vis,TEM,and so on.According to their morphological characteristics,stability and experimental repeatability,four of Au nanoparticles were selected,namely S-,O-,TOH-and HOH-typed,to synthesize four compound materials with different crystal facet indices named S-Au/Ui O-66-NH2,O-Au/Ui O-66-NH2,TOH-Au/Ui O-66-NH2 and HOH-Au/Ui O-66-NH2,respectively.All the samples were characterized by XRD,IR,UV-vis,TEM,photocurrent analysis,and so on.The order of light absorption capacity of Au/Ui O-66-NH2 composites in UV-vis region is consistent with that of corresponding Au nanoparticles,which is O-type>S-type>HOH-type>TOH-type.The photocatalytic hydrogen production performance experiments of these four types of Au/Ui O-66-NH2 were carried out.The photocatalytic hydrogen production rate of O-Au/Ui O-66-NH₂ could reach 7.3151μmol·mg^-1·h^-1,which is 3.3 times that of Ui O-66-NH2 with pure phase,3.2 times that of TOH-Au/Ui O-66-NH2,1.8 times that of HOH-Au/Ui O-66-NH2 and 1.4 times that of S-Au/Ui O-66-NH2.The results showed that compared with S-typed Au nanoparticles without crystal facets,TOH-typed ones with{221}crystal facets and HOH-typed ones with{421}crystal facets,the composite formed by Ui O-66-NH2 and O-typed Au nanoparticles with{111}crystal facets represented better photocatalytic performance.At the same time,it also indicated that the O-typed Au nanoparticles with{111}crystal facets had stronger ability to effectively capture electrons and promote the separation of electrons and holes.19 figures,4 tables and 66 references are showed in this paper.