Photo-catalytic Performance Of TiO₂-based Visible-light Photo-catalyst

Energy shortage and environmental pollution has attracted much attention recently and photo-catalytic semiconductor materials could solve these problems properly,achieve the aims of clean energy production and environmental remediation for pollution.Numerous attempts have been made to develop semiconductor photo-catalysts for decontamination,however it practical application has always been limited by the low utilization rate of visible-light-driven and rapid recombination of electrons and holes.Therefore,the key of above dilemmas was the development of green and efficient visible-light-driven photo-catalytic-system.This thesis focuses on the structure and morphology of TiO₂-based visible-light semiconductor materials,proceed researchs of innovation and optimization for preparation methods of black TiO₂and SnS₂/TiO₂ visible-light photo-catalyst.Utilize varieties of characterization methods include SEM,TEM,XRD,XPS,UV-VIS and N₂-BET to study the morphology structure of material.Visible-light-driven photo-catalytic degradation of dyes and hydrolyzation of hydrogen were studied.The main research contents are as follows:The visible-light material of black TiO₂ nanosheets was successfully prepared by sol-gel method.C₁₆H₃₆O₄Ti as raw material and add CH₃CH₂OH,HNO₃ to form a gel as precursor.And black visible-light TiO₂ material was prepared by burning for a certain time.The optimal black visible-light TiO₂nanosheets material with large specific surface area,anatase phase and highest photo-catalytic activity were prepared under the conditions of 250?,30 min,pH value of 5,and 85%CH₃CH₂OH.The results of TEM showed that black TiO₂ presented irregular nanoscale flakes,with the length of nanoscale flakes ranging from 200 nm to 1000 nm and the width from 50nm to 500 nm.Moreover,the surface of black TiO₂ presented different crystal planes and crystal directions,and the spacing of different crystal directions were 0.270 nm and 0.342 nm,respectively.TEM and XPS results showed that a disordered layer appeared on the surface of black visible-light anatase TiO₂ nanosheets,which was caused by the formation of oxygen vacancy.This structure could provide more traps to capture photogenerated electron-hole pairs.And it can improve visible-light-driven photo-catalytic activity.Then visible-light-driven photo-catalytic degradation of methyl orange?MO?and hydrogen production were studied.The results show that under the simulated sunlight irradiation,black TiO₂ nanosheets can completely visible-light-driven photo-catalytic degradation of MO in 120 min.The black TiO₂showed a higher visible-light-driven photo-catalytic activity to produce hydrogen,and its hydrogen production rate was 71.08?mol·g^-1·h^-1.3D micron SnS₂/TiO₂ was successfully prepared by a simple one-step low temperature solvent thermal of ultrasonic method.In this study,C₁₆H₃₆O₄Ti as raw material and add Sn Cl₄·5H₂O,CH₃CSNH₂ to form solution as precursor.For prepared with the same preparation process.The results of SEM and TEM show 3D micron visible-light SnS₂/TiO₂ with petal-like SnS₂ nanosheets grown on the TiO₂sphere.Additionally,SnS₂ nanosheets were tightly attached to the TiO₂ crystal sphere.The obtained SnS₂/TiO₂ was composed of mixed phases of hexagonal SnS₂ and tetragonal anatase TiO₂,and suggesting that the intensity of diffraction peaks assigned to TiO₂ were decreased due to SnS₂ doped to TiO₂by XRD analyses.However,while increase hydrothermal temperature,the intensity of diffraction peaks will increase.XPS results showed the existence of Sn-O bonds and Sn-S bonds in the composites.The formation of Sn-O bonds and Sn-S bonds in SnS₂/TiO₂ are important for fast electron transfer from the TiO₂ substrate to SnS₂.Furthermore,it confirmed the formation of SnS₂/TiO₂ heterojunctions.The results of UV-vis show that coated SnS₂nanosheets would decrease the band gap of TiO₂ and SnS₂/TiO₂ have good optical absorption capabilities in the visible light area.Moreover,under the same preparation pore size distribution peak at about 1.70?1.80 nm was identified for the different molar ratio of SnS₂/TiO₂ samples by N₂-BET.Combined with the N₂ adsorption desorption isotherm results confirm the narrow pore was thought to be the slit-pores formed by the accumulation of sheet particles.And the small pores presumably arose from the petal-like SnS₂ nanosheets,whereas the large pores could be attributed to the interspace between nanopetals.This SnS₂/TiO₂ could effectively utilize photon energy in the sunlight and simultaneously maintain high electron transfer rate.The SnS₂/TiO₂composites showed the highest visible-light-driven photo-catalytic activity and good stability toward decontamination?taking MO as the model contaminant?.And MO photo-degradation with SnS₂/TiO₂ could all be well fitted by first-order kinetic equation.In order to investigate the mechanism of photo-catalytic degradation of MO on the SnS₂/TiO₂ catalyst,isopropyl alcohol?IPA?,EDTA-2Na and Ag NO₃ were used as the trapping agent in batch experiments for·OH radicals,h⁺and e^-respectively.In this decontamination process,MO was first reduced by the electron and then subjected to be oxidized by the h⁺generated·OH.Or,MO could be directly oxidized by the·OH.Apart from MO,the SnS₂/TiO₂composites could also be applied to effective removal of the other contaminants,like MB and phenol.In this study,the prepared SnS₂/TiO₂is promising visible-light-driven photo-catalyst for practical application in decontamination.