Research On Preparation And Properties Of Molybdenum-based Oxide Nanocomposites

In recent years,due to the rapid development of industry and the continuous growth of population,a large number of waste materials have been produced,resulting in energy shortage and environmental pollution.Therefore,in order to ensure the long-term and sustainable exploitation of human condition,it is emergency to exploit environmentally-friendly and reproducible technologies for pro-environment energy production and environmental reclamation.Semiconductor photocatalysis has great potential in various technologies because it can degrade various pollutants directly and efficiently by solar energy.However,traditional semiconductor materials often have a series of problems(high electron-hole recombination rate and low cycle efficiency)that affect the utilization of sunlight,resulting in low degradation efficiency of pollutants by catalysts.Due to the special electronic layer structure of metal molybdenum ions,under certain conditions,some electronic layers will lose electrons,which promote the transmission of electrons and facilitate the photocatalytic process.In this thesis,a variety of molybdenum-based oxide photocatalysts with one-dimensional nano-morphology were prepared by electrospinning combined with solvothermal technology,and their photocatalytic properties were discussed by characterization.The main research contents and conclusions are as following:1.Co-doped molybdenum trioxide(Co-MoO₃)nanobelts with a diameter of about500 nm were successfully prepared by solvothermal method.The morphology of the nanobelts was not changed by the introduction of cobalt ions.The samples were characterized by XRD,SEM,TEM,XPS,PL and other techniques.The band gap and density of states of the samples were calculated by the first-principles method,and the theoretical results in accordance with the laboratory finding.The MoO₃ nanobelts with different doping amounts were refined to obtain accurate cell parameters to explore the doping mechanism.After doping,the impurity energy level near the valence band and the existence of valence-changing Co ions in the system can promote the transmission of electrons and improve the photocatalytic performance.The photocatalytic degradation of tetracycline test showed that the catalytic effect of 3%Co-doped MoO₃nanobelts was the best to reach 92.3%.2.Iron oxide/molybdenum oxide(Fe₂O₃/MoO₃)nanorods were prepared by solvothermal method.Iron oxide particles were uniformly loaded on the MoO₃nanorods with a diameter of about 200 nm.The catalysts were characterized by XRD,SEM,TEM,UV vis DRS and XPS,and the effects of different iron oxide loadings on the catalysts were compared.The formation of heterojunction promotes the separation of photogenerated electron-hole pairs and improves the catalytic efficiency of the catalyst.When the loading amount of Fe₂O₃ was 30%,Fe₂O₃/MoO₃ nanomaterials showed high photocatalytic activity,and the degradation efficiency of tetracycline by Fe₂O₃/MoO₃ nanorods reached 96.5%.3.Pea-like Fe₂(MoO₄)₃ nanofibers with a diameter of about 125 nm were designed and synthesized by electrospinning.The structure and electrochemical properties of the nanofibers were characterized in detail.In addition,the band gap,density of states,and free energy of crystal plane of the catalyst were calculated by the first-principles.The theoretical calculation outcomes are close to the experimental results.Compared with Fe₂(MoO₄)₃ powders,one-dimensional Fe₂(MoO₄)₃ nanofibers have a larger specific surface area,which provides more active sites for the catalyst.Fe₂(MoO₄)₃ nanofibers showed better degradation performance for ciprofloxacin under simulated sunlight.