Preparation And Photocatalytic Performance Of Tungsten-based And Molybdenum-based Nanomaterials

In the 21st century,mankind faces more new challenges.The two main challenges are environmental and energy issues.The huge environmental and energy pressures restrict the pace of human sustainable development.Therefore,we need to develop new types of clean energy.Solar energy is the total source of various energy sources on the earth.Therefore,how to use,transform and store solar energy efficiently and quickly is the general direction of our research.Semiconductor photocatalytic technology is one of the important means to solve environmental and energy problems with the energy conversion and storage of solar energy as the main core.The development of an effective visible light-driven new photocatalyst is an important subject of this technology.As a traditional photocatalyst,Ti O₂ has a wide energy band gap,a small light response range,and low utilization,which limits its practical use.Applications,so people have turned to new semiconductor photocatalysts to solve problems.In recent years,various polymetal oxide semiconductors,such as Bi₂WO₆,Bi VO₄,Bi₂MoO₆,Sr Ti O₃,La Co O₃,Zn₃(VO₄)₂,SnWO₄,Sn(MoO₄)₂ and other materials have been developed and applied to visible light-driven water decomposition and toxic Degradation of organic pollutants.Among them,SnWO₄ and Sn(MoO₄)₂ have attracted the interest of many researchers due to their low cost and environmental friendliness.In combination with the characteristics of chinese mineral resources,W,Mo,Sn and other elements constituting a new type of photocatalyst are among our resources in China.Rich,fully study the performance laws of photocatalysts composed of them,and develop high-efficiency new photocatalysts composed of them,which has important strategic significance for occupying the commanding heights of solar energy conversion and storage.In this dissertation,the controllable synthesis of tungsten-based nanomaterials SnWO₄and molybdenum-based nanomaterials Sn(MoO₄)₂ were successfully studied.Nanomaterials with different morphologies were successfully synthesized.Based on this starting point,the reaction temperature and time were investigated the effects of factors such as,concentration,morphology,and size on the characterization results and photocatalytic properties of the two materials.This research has the following two parts:(1)By using Na₂WO₄ as the tungsten source and Sn SO₄ as the tin source,a microwave-assisted hydrothermal method was used to synthesize a nested SnWO₄ nanomaterial as a target product without the participation of any structure directing agent,and further by changing the reaction temperature and reaction Time,reactant concentration and heating method were used to synthesize nanomaterials composed of different basic units of nanoparticles,nanowires,and nanosheets,which were sequentially denoted as PNN,NLN,and FLA,and the morphology of three different composition products were analyzed,Structure and other effects on its optical,electrochemical and photocatalytic properties.It was found that the above variables will significantly affect the morphology,structure and performance of the crystalline phase product.Among them,the pre-made nested nanostructures composed of nanowires,due to the large specific surface area,strong light absorption capacity,and high charge separation and transfer efficiency make it have better photocatalytic performance.(2)By using Na₂MoO₄ as the molybdenum source and Sn SO₄ as the tin source,a two-step method was used to synthesize Sn(MoO₄)₂ nanomaterials,and the reactant concentration,microwave temperature,and calcination temperature in the two-step reaction were changed respectively.The products of different morphologies were synthesized,and the influence of different variables on their morphology,structure,and performance was analyzed.The existing chemical laws were derived and their influence mechanisms were explored.