Simple Liquid-phase Method To Prepare One-dimensional Micro-nano Materials And Research On Visible Light Catalytic Performance

With the development of the global economy,energy shortages and environmental pollution have become increasingly prominent,which affects the sustainable development of mankind.As a green and clean technology,visible light catalysis is used to replace traditional high-energy treatment methods and degrade organic pollutants in wastewater,which has become research focus.Many catalysts reported in the literature show photochemical activity only in the ultraviolet region.In the solar spectrum,the ultraviolet light accounts for less than 5%,and the visible light accounts for 43%.Therefore,it is of great significance to utilize sunlight effectively and develop photocatalytic materials with high activity in visible light.One-dimensional micro-nano materials have two characteristics of one-dimensional and micro-nano materials.Compared with two-dimensional and three-dimensional materials,their geometric structures are more favorable for carrier transport and show superiority in photocatalysis.In recent years,semiconductors such as TiO₂,ZnO and lanthanide compounds have been used as photocatalytic materials,but they have been restricted in their forbidden band width and poor in light stability.In order to improve their performance,researchers have focused their attention on doping,recombination and other methods to optimize the photocatalytic performance of the semiconductor compound,which in turn makes the preparation process of the photocatalyst material cumbersome or requires high preparation conditions.The appearance of elemental semiconductor materials as a photocatalyst not only enriches the types of photocatalytic materials,but also its simple preparation process has become a direction for the development of new photocatalytic materials.In addition,vanadium bronze materials have been used in secondary batteries,supercapacitors,etc.for their excellent electrochemical properties in recent years,and there are few studies on photocatalytic treatment of organic pollutants.Therefore,the study on the photocatalytic properties of vanadium bronze is helpful to broaden the types of photocatalytic materials.It has been reported in the literature that different preparation methods are used to prepare selenium and sodium vanadate materials with different morphologies,but it is still a challenge to prepare one-dimensional selenium and sodium vanadate by simple solution-phase method.In this paper,one-dimensional selenium nanowires and sodium vanadate nanorods were prepared by simple solution-phase method.Two methods were used for the preparation of selenium nanowires:chemical solution-phase method and hydrothermal method.The crystal structure,morphology and light absorption characteristics of the prepared selenium and sodium vanadate were characterized by XRD,SEM,TEM,BET,XPS and Uv-Vis.The growth mechanism and the mechanism of morphology change were discussed based on the experimental results.The photocatalytic performance of the materials were investigated by measuring the degradation rate of the organic dyes,including methylene blue and methyl orange.The main research work is divided into the following three parts:1.With the aid of the surfactant cetyltrimethylammonium bromide?CTAB?,the selenium dioxide?SeO₂? is reduced by simple chemical liquid method at 50? to obtain single crystal selenium nanowires with a diameter of about 100-200 nm and a length of 10?m,of which sodium formaldehyde sulfoxylate?SFS? was first used as reducing agent for the preparation.By controlling the change of single reaction parameters,the influence of reaction temperature and surfactant CTAB on the morphology of the product was investigated.The optimum temperature for preparing selenium nanowires was 50?,and the optimum surfactant dosage was 0.1 g.Selenium nanowires with good dispersibility can be prepared in a shorter time and at lower temperature than the reported literature.In addition,the“solid-liquid-solid”growth mechanism of selenium nanowires was proposed.The visible light catalytic performance of the prepared selenium nanowires was investigated by catalyzing methylene blue?MB?.The results show that selenium nanowires can degrade over 99% of MB in 3 hours under the synergistic action of H₂O₂.2.Selenium dioxide was reduced by solvothermal method at 180? to obtain single crystal selenium nanowires.Rutin?vitamin P?was used as a reducing agent for the first time to prepare selenium nanomaterials and ethanol as a solvent.The growth mechanism of selenium in ethanol and water was proposed.It was found to trigonal crystal selenium grows into a linear form in ethanol,amorphous selenium grows into a spherical shape in water.When ethanol and water coexist,the surface of the linear selenium becomes rough,and the surface of the spherical selenium has a depression.The selenium nanowires obtained in ethanol were compared with the amorphous selenium micro-nanospheres obtained in water.It was found that selenium nanowires catalyzed that methyl orange?MO? was faster than selenium micro-nanospheres,and the degradation rate of selenium nanowires reached 98.09%?3 h?,and the degradation rate of selenium microspheres was only 13.86%,which was unstable.But the catalytic methylene blue was slower than selenium micro-nanospheres.The degradation rate of selenium nanowires was 25.33%,the rate reached 97.42% while selenium micro-nanospheres degraded by 2 h,which indicats that the selenium micro-nano materials are selective in visible light catalysis.The optical band gap was analyzed by ultraviolet-visible absorption,the specific surface area and pore size distribution of the catalyst were analyzed by surface structure,and the photocatalytic behavior analysis was used to clarify the difference of visible light catalytic performance between selenium nanowires and selenium.3.The nanoflower-like HNaV₆O₁₅·4H₂O consisting of nanorods was prepared by hydrothermal method.After calcination,nanorod-like NaV₆O₁₅ was obtained.Firstly,the crystal structure and morphology of the precursor were characterized,and the changes of crystallinity and morphology with reaction time were discussed.After characterization of NaV₆O₁₅,it is a single crystal nanorods.By comparing the UV-visible absorption spectra of the precursors HNaV₆O₁₅·4H₂O and NaV₆O₁₅,the visible light response threshold of the calcined NaV₆O₁₅ nanorods is red-shifted and the forbidden band width becomes smaller.Visible light catalysis of MB was used to evaluate and compare the visible light catalysis performance of the two materials.The experimental results show that:HNaV₆O₁₅·4H₂O has better catalytic performance than NaV₆O₁₅.Compared with similar vanadium bronze materials,the degradation rate of NaV₆O₁₅?20 mg? in 3 hours for 20mg/L MB solution was 88.62%,while that of HNaV₆O₁₅·4H₂O?20 mg? in 20 min was 98.39%.The results show that sodium vanadate has good visible light catalytic performance and application prospects.