Study On The Preparation And Photocatalytic Properties Of Carbon Nano Onions/Titanium Dioxide/Silicon Dioxide Nanocomposites

Since twenty-first century,the process of industrialization and urbanization in China has been greatly accelerated.Water environmental problems such as the eutrophication of water and the odor of water quality have become global issues that are urgently needed to be resolved.And this environmental poses a great threat to the sustainable development of our country’s economy and society.Therefore,building a harmonious and beautiful ecological environment and developing clean and sustainable water treatment technology is a huge task for scientists.Semiconductor photocatalytic technology is an effective,sustainable,environmentally friendly and economical solution to environmental pollution.Titanium dioxide（TiO₂）has been widely used due to its stable chemical properties,non-polluting and low cost.However,because of the large band gap,low quantum yield and smaller surface area of TiO₂,it is not conducive to the enrichment of pollutants,which limits its application in the environment and energy fields.Therefore,the research of nano TiO₂ new material,improve its structure and properties,preparation plays an important role in composite photocatalyst has excellent photocatalytic properties.In this dissertation,composite photocatalysts with good photocatalytic properties were prepared by combining titanium dioxide with carbon nano onions and silica.And its microstructure and photocatalytic activity were also tested.The main experimental contents and results were achieved as follows:CNOs/TiO₂ composite photocatalyst was prepared by sol-gel method,and its microstructure was characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）,specific surface area and pore structure distribution（BET）,Fourier transform infrared spectroscopy（FT-IR）,TG-DSC and ultraviolet-visible diffuse reflectance spectroscopy（UV-vis DRS）.The photocatalytic performance of rhodamine B,which was difficult to biodegrade,was used to evaluate the photocatalytic performance of CNOs/TiO₂ composite photocatalyst.Based on the experiment of free radical capture,the degradation mechanism of organic pollutants on CNOs/TiO₂ composite photocatalyst was preliminarily explored.The result showed that the samples exhibited the best photocatalytic activity when the mass ratio of CNOs to TiO₂ was 10%.Radical tripping experiments showed that hole and superoxide free radical play a major role in photocatalytic reactions.Experiments show that CNOs not only enhanced the absorptive capacity of the catalyst material to light,but also had excellent electron enrichment ability.It could transfer photoelectrons to CNOs,restrain light electron hole compound and improve the efficiency of the separation of the pair.CNOs/TiO₂/SiO₂ composite photocatalyst was prepared by sol-gel method and characterized by XRD,SEM,XPS,BET,FTIR and UV-vis DRS.The catalytic activity of RhB in CNOs/TiO₂/SiO₂ composites under visible light was studied.The research indicated that the activity of CNOs/TiO₂/SiO₂ composite was higher than that of CNOs/TiO₂ under visible light and had better degradation effect on rhodamine B.Radical scavenging experiments showed that superoxide anion played a leading role in the degradation of organic pollutants.Further studies have found that the composite of SiO₂ increased the surface area of the samples,improved the adsorption of contaminants,and diffused hydroxyl groups to the surface of SiO₂.The synergistic effect of CNOs and SiO₂ can effectively inhibit the recombination of photogenerated electron-hole pairs and enhances the photocatalytic activity of the sample,which is a key factor for the composite material to effectively degrade rhodamine B.