The Preparation Of S,Zr And S-Zr Doped TiO₂ Photocatalysts By Miccrowave Hydrothermal Method And Their Photocatalytic Activity Research

In this paper,three types of doped photocatalysts were prepared by microwave hydrothermal method,namely sulfur,zirconium single-doping?TiO₂-S,TiO₂-Zr?and zirconium-sulfur co-doping?TiO₂-Zr-S?.Cross test and single factor experiment,specifically analyze the following factors:the doping ratio,the setting parameters of the microwave hydrothermal parallel synthesizer?synthesis power,synthesis temperature,synthesis time?,the muffle furnace?calcination temperature,calcination time?Of doped photocatalyst activity;using methyl orange solution(10mg.mL^-1)as a simulated pollutant to change catalytic degradation conditions:homemade UV lamp,microwave?MW?,microwave-ultraviolet?MW-UV?,microwave-Ultrasonic-ultraviolet?MW-UT-UV?was used to perform photocatalytic degradation experiments to investigate the effects of different catalytic degradation conditions on the photocatalytic activity of three doped photocatalysts;the three catalysts subjected to catalytic degradation were washed and dried.Dry and repeatedly put in the degradation experiment of methyl orange solution to investigate the stability of three doped catalysts.Finally,through X-ray diffraction analysis?XRD?,scanning electron microscope analysis?FESEM?,X-ray energy spectrum analysis?XPS?,N₂adsorption-desorption analysis?BET?,thermogravimetric analysis?TG-DTG?,ultraviolet-visible Diffuse reflection spectroscopy?UV-Vis?,fluorescence spectroscopy?PL and PEL?,infrared spectroscopy?FTIR?and other modern analytical testing techniques are used to analyze the surface morphology and internal structure of the three doped TiO₂ photocatalysts.Characterization analysis to study the effect of changes in the structure and morphology of the doped catalyst on its photocatalytic activity.The results obtained are as follows:1.Preparation of La-doped TiO₂Photocatalyst and Its Photocatalytic Activity by Microwave Hydrothermal Method and its photocatalytic activityThe optimal conditions for the preparation of TiO₂-S photocatalyst by microwave hydrothermal method are:the setting parameters of the microwave hydrothermal parallel synthesizer are:synthesis temperature 150°C,synthesis time2.5 h,synthesis power 550W,calcination temperature 600°C,and calcination time2.5 h,n(S⁶⁺):n(Ti⁴⁺)=1.0?ratio of the amount of matter?.The degradation rate of TiO₂-S photocatalyst for methyl orange solution was 96.41%when the catalytic degradation condition was UV lamp?home-made?irradiation for 30min;and the catalytic degradation conditions were MW,MW-UV and MW-UT-UV,respectively.The degradation rate of TiO₂-S photocatalyst for methyl orange solution was 10.20%,98.99%and 99.90%when reacted for 40 min under the conditions.When the catalytic degradation condition was visible light,after 4 h reaction under visible light,TiO₂-S light The catalyst can almost completely degrade the methyl orange solution.XRD and FESEM analysis results show that the TiO₂-S catalyst prepared by the microwave hydrothermal method has the characteristics of high crystallinity and uniform particle size,etc.,and the clustering phenomenon caused by the limitations of the microwave hydrothermal synthesis method;N₂ adsorption-desorption test The analysis shows that TiO₂-S is a mesoporous material with uniform pore size distribution,and has a larger surface area and more active sites,so TiO₂-S has higher photocatalytic activity;EDS and XPS test analysis shows TiO₂-S contains Ti,O,C,and S elements.S mainly exists in TiO₂ in the form of+6 sulfate(SO₄^2-).SO₄^2-is introduced into the TiO₂ lattice,which reduces the catalyst band.The analysis of PL and PEL tests shows that sulfur doping greatly inhibits the recombination rate of photogenerated electrons and holes of TiO₂-S photocatalyst,prolongs the lifetime of photogenerated electron-hole pairs,and improves its photocatalytic activity.The UV-Vis test shows that,compared with pure TiO₂,the TiO₂-S photocatalyst moves in the direction of the long wave of visible light,causing a red shift,which improves the utilization of visible light.The doping of S makes the crystal phase structure of TiO₂change,the band gap decreases,the specific surface area increases,and the recombination ratio of photogenerated electrons and holes decreases,so the photocatalytic activity of the TiO₂ catalyst is improved.2.The Preparation of the TiO₂-Zr photocatalyst by microwave hydrothermal method and its photocatalytic activityThe optimal conditions for the preparation of TiO₂-Zr photocatalyst by microwave hydrothermal method are:the setting parameters of the microwave hydrothermal parallel synthesizer are:synthesis temperature 150°C,synthesis time2.5 h,synthesis power 550 W,calcination temperature 600°C and calcination time2.5 h,n(Zr⁴⁺):n(Ti⁴⁺)=0.04?ratio of the amount of matter?.The degradation rate of TiO₂-Zr photocatalyst for methyl orange solution was 97.10%when the catalytic degradation condition was UV lamp?home-made?irradiation for 30 min;and the catalytic degradation conditions were MW,MW-UV and MW-UT-UV,respectively.When reacted for 40 min under the conditions,the degradation rates of TiO₂-Zr photocatalyst for methyl orange solution were 10.90%,99.98%and 100%respectively.When the catalytic degradation condition was visible light,after 4 h of reaction under visible light,TiO₂-Zr light The catalyst can almost completely degrade the methyl orange solution.XRD and FESEM analysis results show that TiO₂-Zr has a single crystal form,high crystallinity,small particle size and uniform distribution.The analysis of N₂ adsorption-desorption test shows that the TiO₂-Zr photocatalyst has a small pore size,a regular structure,a large specific surface area,With more active sites,TiO₂-Zr has higher photocatalytic activity;XPS test analysis shows that XPS test analysis shows that TiO₂-S contains Ti,O,C,and Zr elements,and Zr is mainly priced at+4 ZrO₂ exists on the surface of TiO₂ photocatalyst.ZrO₂ will reduce the band gap of the photocatalyst,thereby improving the photocatalytic activity of TiO₂-Zr.PL and PEL test analysis shows that Zr doping makes TiO₂-Zr The recombination rate of photogenerated electrons and holes in the photocatalyst is reduced,that is,the life of the photogenerated electron-hole pair is extended,and the activity of the TiO₂-Zr photocatalyst is enhanced.The UV-Vis test shows that both TiO₂-Zr and TiO₂-S will move?redshift?in the long-wave direction of visible light.The former has a more obvious redshift phenomenon and a higher utilization of visible light.Zr doped with TiO₂ increased its crystallinity,crystal phase change,specific surface area,and active sites,which increased the photocatalytic degradation activity of TiO₂ catalyst.3.Preparation of the TiO₂-Zr-S photocatalyst by microwave hydrothermal method and its photocatalytic activityThe optimal conditions for the preparation of TiO₂-Zr-S photocatalyst by microwave hydrothermal method are:the setting parameters of the microwave hydrothermal parallel synthesizer are:synthesis temperature 150°C,synthesis time2.5 h,synthesis power 600 W,calcination temperature 600°C,calcination time 2.5 h,[n(Zr⁴⁺):n(Ti⁴⁺)=0.04,n(S⁶⁺):n(Ti⁴⁺)=1.0]?ratio of amount of matter?.The degradation rate of TiO2-Zr-S photocatalyst for methyl orange solution was 97.82%when the catalytic degradation condition was ultraviolet lamp?home-made?irradiation for 30 min;and the catalytic degradation conditions were MW,MW-UV and MW-UT,respectively.The degradation rate of TiO₂-Zr-S photocatalyst for methyl orange solution was 11.24%,99.98%and 100%when the reaction was carried out under-UV condition for 40min.When the catalytic degradation condition was visible light,the reaction time under visible light was 3.5 h,TiO₂-Zr-S photocatalyst can almost completely degrade methyl orange solution.XRD and FESEM analysis results show that the TiO₂-Zr-S photocatalyst has high crystallinity,small grains and uniform size,and clusters are formed due to the limitations of the synthetic method and uneven physical grinding;the analysis of the N₂ adsorption-desorption test is It shows that TiO₂-Zr-S has the advantages of large specific surface area,small pore size,and regular structure of pores.Therefore,TiO₂-Zr-S has higher photocatalytic activity;XPS test analysis shows that TiO₂-Zr-S contains Ti,O,C,Zr elements,Zr exists on the surface of TiO₂ with zirconium oxide?ZrO₂?of+4 valence,which reduces the band gap of the photocatalyst;S mainly exists in the TiO₂ gap in the form of+6valence ions,thereby reducing Bandwidth of small catalyst.The PL and PEL test analysis shows that due to the doping of S and Zr,the photoelectron-hole recombination rate of the catalyst decreases,the lifetime of photo-generated electrons-holes is extended,and its photocatalytic activity is improved.The UV-Vis test shows that compared with S or Zr-doped TiO₂,the TiO₂-Zr-S photocatalyst moves the longest distance in the visible light wave direction,further increasing the utilization of visible light.Zr and S co-doped with TiO₂ changed the crystalline phase composition ratio,specific surface area,band gap width,and photo-generated electron-hole lifetime of TiO₂,and further improved the photocatalytic degradation activity of TiO₂ catalyst.The results in this paper show that the three doped TiO₂ photocatalysts?TiO₂-S,TiO₂-Zr,TiO₂-Zr-S?obtained by microwave hydrothermal method under the optimal preparation conditions all have good photocatalytic activity.The reaction results of the three doped photocatalysts under different catalytic degradation conditions show that microwave and ultrasound can assist the catalytic degradation process of TiO₂photocatalyst,and the photocatalytic activity of TiO₂ can be further improved.The catalyst prepared under the microwave hydrothermal method is carried out in a closed environment at high temperature and high pressure.There is no temperature gradient.The reactants can be uniformly heated,and it can dissolve some hardly soluble or insoluble substances in conventional hydrothermal methods.)4 colloid can be well nucleated,and then recrystallized,separated and calcined at high temperature to prepare a photocatalyst with high crystallinity and uniform particle size,and its photocatalytic activity is good.This provides an energy-saving,efficient and environmentally friendly green approach for the preparation and practical production of doped TiO₂ photocatalysts,and enriches the research content of microwave chemistry.