Synthesis Of S Modified TiO₂ On Reduced Graphene Oxide Al₂O₃ Composites As The Photocatalyst And The Studies Of Their Photocatalytic Performance

TiO₂ photocatalyt has been widely used in the field of environment and energy,such as surface cleaning,air and water purification system,sterilization,photoelectrochemical conversion.TiO₂ nano materials is the most studied photocatalyst owing to its high photocatalytic activity,strong oxidation ability,good chemical stability,durability,non-toxic and low cost,and it also can decompose certain types of organic compounds completely to carbon dioxide and water.However,due to the wide band gap of TiO₂ photocatalyst,it can only absorb ultraviolet light,unfortunately,ultraviolet light accounts for about 4%of the sunlight,so the sunlight energy utilization rate is low.The photogenerated electron-hole pairs by titanium dioxide is easy to recombine,and result in the low efficiency of the photogenerated carriers.In addition,the titanium dioxide is difficult to be recycled.These defects have limited the extensive application of titanium dioxide.How to improved the photocatalytic activity of TiO₂,cyclic utilization and expand the response spectrum of TiO₂ photocatalytic activity in the visible light region has always been a research hot spot.The shortcomings of titanium dioxide may be overcomed through loading of TiO₂ on a carrier.Carrier generally has some characteristics,such as large specific surface area,strong adsorption,effective separation of electrons and holes,magnetism,easy recycling,etc.Thus,it not only can improve the effect of degradation,but also is beneficial to the regeneration of the carrier.Through S elements doping,titanium dioxide can response to visible light response.In this paper,we prepared the graphene modified alumina composite as carrier,and the effect of composite carrier on the properties of TiO₂ photocatalysis were studied.In the experiment,reduced graphene oxide?RGO?-modified Al₂O₃ composites were prepared by precipitationmethod.TiO₂ nanoparticles were dispersed on the surface of the RGO-Al₂O₃ composite by impregnation method using tetrabutyl titanate as precursor.S modified TiO₂ supported on RGO-Al₂O₃ composites were synthesized by impregnation method using thiourea as a source of sulfur.The photocatalyst were characterized and analyzed by Raman spectroscopy,XRD,DRS,XPS,SEM and TEM characterization methods.Take the degradation of methyl orange as the goal,the efficiency of photocatalyst under the ultraviolet and visible light were studied.?1?Preparation and characterization of the graphene oxide?GO?modified Al₂O₃?GO-Al₂O₃?In this experiment,aluminum nitrate as aluminum source was used to prepared GO modified Al₂O₃ composite carrier?GO-Al₂O₃?and RGO modification of Al₂O₃carrier?RGO-Al₂O₃?through precipitationmethod.XRD results show that the prepared of composite carrier was the amorphous structure,due to the small size of alumina particle and high dispersion.N₂ adsorption-desorption measurements results show that the RGO-Al₂O₃ composite carrier has mesoporous structure,has a large specific surface area?423 m²/g?.The larger specific surface area is conducive to the adsorption of materials that to be degraded,and provide more active site.As the carrier of TiO₂,RGO-Al₂O₃ composite carrier not only has a large specific surface area and the ability to store electrical,but also can effectively control the size and dispersion of the TiO₂particles.?2?The preparation and studies of TiO₂/RGO-Al₂O₃ composite catalystIn this experiment,TiO₂ nanoparticles were dispersed on the surface of the RGO-Al₂O₃ composite by impregnation using tetrabutyl titanate as precursor.The surface properties of TiO₂/RGO-Al₂O₃ were systematically studied.by Raman spectroscopy,XRD,DRS,XPS,SEM,UV-Vis DRS and TEM.We found that the TiO₂ crystal size was about 15 nm,and the crystals were relatively uniform in the loading range of 20-40 wt%compared with that of Al₂O₃.The surface area increased obviously as RGO was added to Al₂O₃.The chemical structures of the TiO₂/RGO–Al₂O₃ composites were characterized by diffuse reflectance UV-visible spectroscopy and X-ray photoelectron spectroscopy.Results revealed the presence of an intense interaction between TiO₂ and RGO-Al₂O₃.The liquid-phase photocatalytic oxidation of methyl orange was adopted to evaluate the activity of the obtained materials.TiO₂/RGO-Al₂O₃ showed higher catalytic activity than the TiO₂/Al₂O₃ or the commercial P25 photocatalyst.?3?The preparation and studies of S doped TiO₂/RGO-Al₂O₃ composite catalystIn this experiment,S modified TiO₂ on RGO-Al₂O₃ composites were synthesized by impregnation method using thiourea as a source of sulfur.S-TiO₂/RGO-Al₂O₃ were characterized by X-ray diffraction?XRD?,N₂ adsorption–desorption measurements,scanning electron microscope?SEM?,UV-vis diffuse reflectance spectra?DRS?.and the photocatalytic activity was evaluated under visible light.XRD analysis showed that the crystalline phase of S-TiO₂/RGO-Al₂O₃ were anatase.No diffraction peak in the XRD spectrum of sulfur compound was found,but element analysis prove the existence of sulfur,which suggests that S may enter to the interior TiO₂ crystal lattice.S-TiO₂/RGO-Al₂O₃ improve its visible light catalytic activity.In this experiment the best sulphur content was 3%.The Sulfur will enter into the lattice of TiO₂,and the lattice structure of TiO₂ produced a minor change.However,excess sulfur doping decrease the catalytic activity.S-TiO₂/RGO-Al₂O₃ composite catalyst is easy to be recycled.