Preparation Of WO?(3-x) Flims And Study On Photocatalytic Performance

Photocatalysis technology uses sunlight to drive the reaction,which has the characteristics of low cost and low pollution.It is also an ideal means to improve reaction efficiency.Its core is the development of photocatalyst.Therefore,the development of a high-efficiency photocatalyst is of great significance in the fields of chemical production and environmental governance.Tungsten oxide is often used as a photocatalyst in various catalytic reactions due to its small band gap and stable chemical properties.However,tungsten oxide still has the problems of high electron-hole recombination rate and low light absorption intensity,which limits its further application.Therefore,improving the photocatalytic efficiency of tungsten oxide through reasonable modification of the catalyst has always been a research hotspot.In this study,a high-efficiency photocatalyst was prepared by introducing oxygen vacancies in tungsten oxide films and surface-modified Ag nanoparticles by using magnetron sputtering method and its photocatalytic performance was studied.The main content is divided into the following two parts:?1?In this part,non-stoichiometric oxygen-deficient tungsten oxide films(WO_3-x)were prepared on the surface of flat glass by reactive magnetron sputtering method to improve the photocatalytic performance of tungsten oxide film.The effects of argon-oxygen ratio on the film phase,chemical valence state and valence band position were studied;The surface morphology,absorbance,and element valence of WO_3-xfilms were analyzed by AFM,SEM,UV-Vis,XPS,PL,etc.The results show that as the oxygen flow rate decreases,the oxygen vacancy content of films increases,the absorption curve"red shifts".The introduction of oxygen vacancies effectively reduces the width of the forbidden band of the films.In addition,the position of the conduction band moves up,and the redox capacity is enhanced.When the flow rate of oxygen in the reaction gas is 2sccm,the band gap of the WO_3-xfilms is 2.31 e V,and the absorption intensity of visible light reaches more than 0.8 a.u.The performance of photocatalytic degradation of methylene blue and photocatalytic cyclohexane oxidation was tested under a 200 W xenon lamp.In the experiment of photocatalytic degradation of 100 m L of methylene blue at a concentration of 10 mg/L,the reaction was carried out at room temperature for 2hours.The degradation rate of methylene blue by WO_3-xfilms was 70.6%,which was18.3%higher than that of WO₃films.The constant was 0.610 h^-1,which was 1.77 times that of WO₃films.In the photocatalytic cyclohexane oxidation experiment,tert-butyl hydroperoxide was used as the oxidant,and the molar ratio of oxidant to cyclohexane was 1.5:1.The reaction was carried out under normal temperature and pressure for 36hours.The conversion rate of cyclohexane was 5.3%,which was 1.5%higher than that of WO₃film,and the selectivity of KA oil was 70.5%.Compared with tungsten oxide films prepared under other oxygen flow conditions,WO_3-xfilms prepared under 2 sccm oxygen flow condition shows relatively highest catalytic performance in the degradation of methylene blue and cyclohexane oxidation.?2?In order to further improve the photocatalytic performance of the oxygen-deficient tungsten oxide films(WO_3-x),the dual-target co-sputtering technique was used to modify Ag nanoparticles with different contents on the surface of the WO_3-xfilms.SEM shows that Ag nanoparticles are evenly distributed on the surface of WO_3-xfilms,and the size are between 30 and 50 nm.Ag nanoparticles affect the performance of WO_3-x/Ag from two aspects:Firstly,the presence of Ag nanoparticles effectively inhibits the recombination of photogenerated electron-hole pairs.With the increase of Ag content,the recombination rate of electrons and holes decreases,and resulting fluorescence intensity continues to decrease.Secondly,the SPR effect is used to increase the light absorption intensity of the films in the visible light region.The increase of Ag content increases the absorption intensity of films in the near infrared region.When the Ag content is 6.2%,the absorption intensity of WO_3-x/Ag is the highest.As the Ag content further increases,the absorption capacity of WO_3-x/Ag is suppressed.In the photocatalytic performance test,WO_3-x/Ag with an Ag content of 6.2%showed the best performance.After 2 hours of photocatalytic degradation of methylene blue,the degradation rate of methylene blue by WO_3-x/Ag was 93.6%,which was 23%higher than that of WO_3-x.The reaction constant k was 1.249 h^-1,which was 2.05 times that of WO_3-x.In the photocatalytic cyclohexane oxidation experiment,the reaction was carried out for36 hours.The conversion rate of cyclohexane was 6.1%,which was 0.8%higher than that of WO_3-xfilms,and the selectivity of KA oil was 71.6%.