Controllable Preparation and Performance Study of Novel Metal-based Photocatalysts

Author:Liu Zuo Zuo

Supervisor:cui xiao qiang

Database:Doctor

Degree Year:2019

Download:51

Pages:134

Size:8842K

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Photocatalysis provide a new way for solving the problems of energy exhaustion and environmental pollution.In recent years,this technology has been widely developed with emerging various photocatalysts,in which basically includes metal-based photocatalysts and non-metal-based photocatalysts.A large number of studies have shown that there are two main factors restricting the performance of photocatalysts:the absorption range,and the separation/transportation of photoexcited electrons and holes.Designing photocatalysts with efficient activity is a research hotspot in the field of photocatalysis.In this thesis,we prepared a series of novel metal-based photocatalysts and modulated their photocatalytic performances by constructing heterostructures and controlling their structural configuration.The main research contents and conclusions are as follows:(1)Using the strategy of constructing heterostructures,we combined one metal-organic framework structure UiO-66-NH2 with another metal-organic framework structure MIL-101(Fe),resulting in a dendritic bi-MOFs heterostructure(UiO-66-NH2@MIL-101(Fe)).The heterostructures exhibit excellent photocatalytic oxidation performance of styrene.We found that UiO-66-NH2@MIL-101(Fe)showed a large absorption range compared with pure UiO-66-NH2.At the same time,the conduction band and valence band position of UiO-66-NH2 are well-matched with that of MIL-101(Fe)forming a typical type II structure,which effectively promoted the separation of electrons and holes.These factors lead to a significant increase in catalytic activity.(2)According to the concept of constructing Schottky heterostructures,we design and prepare UiO-66-NH2/Ti3C2 MXene heterostructures.UiO-66-NH2 is positive charged,and Ti3C2 MXene two-dimensional material shows negative charge.The two materials are combined due to the strong electrostatic adsorption.After the UiO-66-NH2/Ti3C2 MXene heterostructure is excited by visible light,thanks to the metalloid of Ti3C2 MXene,the electrons located in the conduction band of UiO-66-NH2 are effectively transferred to Ti3C2 MXene,which effectively inhibits the recombination of electrons and holes.At the same time,the introduction of Ti3C2 MXene brodens the absorption range to visible light.The heterostructure shows enhanced catalytic performance than pure UiO-66-NH2 for the degradation of rhodamine B under visible light.(3)Spiral BiOCl Moire?superlattice nanosheets are prepared by one-step solvothermal method based on a novel structure controlling strategy,which is different from the previous methods for preparing Moire?superlattice two-dimensional materials(mechanical stacking and chemical vapor deposition).Our method is very simple,reproducible,and mass-produced.The BiOCl Moire?superlattice nanosheets shows a significantly lower band gap and can absorb visible light compared with the conventional BiOCl nanosheets.The carrier lifetime is increased,indicating that the electrons and holes are effectively separated.The first principle calculation reveals the mechanism beneath this phenomenon.The main reason is that there are new stacking structures between the two layers in Moire?superlattices,which leads to a strong interlayer coupling interaction,thus resulting in the decrease of bandgap and the increase of carrier concentration.Different from the conventional modification of BiOCl(doping elements or compounding other semiconductor materials),we exploit the idea of formation of two-dimensional Moirésuperlattice and provide a clean modification of BiOCl without introducing any external elements/materials.BiOCl Moirésuperlattice nanosheets shows enhanced catalytic activity for photocatalytic degradation of pollutants.