Aqueous Synthesis And Property Study Of Molybdenum-based Semiconductors And Composites

With the continuous development of nanotechnology and nanomaterials research,many countries in the world have studied and developed the application of nanomaterials and made efforts to make their industrialization.Molybdenum based oxides and their composite oxide micro/nano materials have good optical and electrical properties compared with other materials,and have high stability.They have great potential in the fields of electrochromic,photochromic,catalysis and intelligent windows.The optical and catalytic properties of Mo based micro/nano materials are affected by their structure,morphology and composition,therefore,controlling the synthesis of molybdenum based oxides and their composite micro/nano materials with special structure,morphology and composition is of great significance to improve their application performance.In this thesis,the h-MoO3 microrods,WO3-MoO3 hollow microsphere and TiO2-MoO3 microflower compound oxide were synthesized successfully under water bath condition by using a mild liquid phase synthesis method,add organic small molecules and other elemental oxides during the synthesis process.The morphology,structure,photochromic properties and photocatalytic properties of the synthesized materials were studied.The specific research work of this paper is given as follows:First,using chitosan as the inducer,ammonium molybdate and hydrochloric acid as reactants,the chitosan and hydrochloric acid are mixed uniformly at room temperature,and then the h-MoO3 microflowers are synthesized at 90℃.By changing the reaction time,the amount of hydrochloric acid,the order of the added reagents,the reaction temperature and the amount of chitosan to examine their effect on the size and morphology of the sample.The samples were tested by UV-vis and photochromic properties,the results showed that with the increase of the chitosan content,the sample would have a marked red shift,the photochromic properties of the samples were enhanced with the increase of the chitosan content.Therefore,the size and morphology of the product can be controlled by controlling different reaction conditions,so as to improve the performance of the sample.Second,under the condition of ordinary pressure at 60℃,using a simple liquid-phase synthesis method and by adding a small amount of sodium tungstate,because Mo and W elements are in the same race and similar in nature,the nucleation rate of WO3 is much larger than that of MoO3,So WO3 is used as the nucleus,to successfully synthesize WO3-MoO3.composite oxide nanomaterials.The morphology and size of the samples were regulated by changing the amount of sodium tungstate and hydrochloric acid,reaction time,reaction temperature and the surfactant content.The experiment found that the amount of surfactant has a great influence on the photochromic properties of the sample,as the amount of surfactant increases,the properties of the sample increased,this was mainly due to the reducibility of the hydroxyl groups in the surfactant PEG 6K,which could provide electrons in the process of discoloration.This section provides a new idea for exploring the conditions and developing superior properties of synthetic oxide composites under mild conditions.Third,synthesis Ti02 as the nucleus fistly,and adding the ammonium molybdate solution to synthesize the TiO2-MoO3 composite oxide material.The size and morphology of the sample were adjusted by controlling the ratio of Ti/Mo,the reaction time when TiO2 was formed,the growth time after the addition of the ammonium molybdate,and the surfactant.The photocatalytic degradation of the composite oxide samples obtained from different Ti/Mo ratios showed that the photocatalytic degradation performance of composite oxide was greatly improved compared with the pure h-MoO3,when the Ti/Mo ratio is 1:2,the pure degradation rate of the sample is the highest.In a few words,a series of molybdenum-based oxides and complex oxides were synthesized by a simple liquid-phase precipitation method,the size and morphology of the samples can be controlled by controlling the reaction conditions.The performance of the samples were tested,it is show that the molybdenum-based composite oxides are superior to pure molybdenum oxides both in terms of photochromic properties and photocatalytic degradation properties.