The Research On Doping Modification And Photocatalytic Performance Of TiO₂/CoAl-LDH

As a promising wastewater treatment technology,photocatalysis technology is constantly developing.Among many photocatalysts,TiO₂ is the most studied photocatalyst due to its non-toxicity,good chemical stability,and strong oxidizing ability.In recent years,CoAl-LDH has developed rapidly as a new visible lightresponsive photocatalyst,but both have the problem of easy carrier recombination,and TiO₂ only responds in the ultraviolet region.The composite of TiO₂ and CoAl-LDH is a kind of method that can effectively improve the photocatalytic effect,but the use of visible light is still small.Therefore,this paper chooses TiO₂ and CoAl-LDH composite as the basis and optimizes the modification to prepare two composite systems.One is the use of the noble metal Ag loaded modification to form a ternary material system,and the other is for the doping modification of TiO₂.The hollow N-TiO₂ and CoAlLDH are composited.The specific research is as follows:Firstly,the process parameters for preparing CoAl-LDH are explored.The microwave hydrothermal method and traditional hydrothermal method are used to prepare CoAl-LDH at different times and temperatures.The morphology and phase analysis of the prepared samples are finally determined.The best experimental parameter is the microwave hydrothermal method,the reaction temperature is 120℃,and the reaction time is 2h.Compared with the traditional hydrothermal method,the efficiency is increased by 12 times.Then use microwave hydrothermal method to prepare TiO₂/CoAl-LDH composite material,where the content of TiO₂ is variable,and the photocatalytic activity of TiO₂/CoAl-LDH composite system is improved.Among the materials with the best photocatalytic performance,TiO₂ and CoAl-The compound ratio of LDH is 1:10,which can degrade 68% of methylene blue under two hours of visible light irradiation.Subsequently,Ag was loaded by photoreduction method,TiO₂/CoAl-LDH/Ag was analyzed and characterized and its photocatalytic mechanism was studied.Absorption spectroscopy and electrochemical tests showed that the absorption and separation of light were greatly improved due to the addition of silver.The catalytic degradation efficiency is significantly improved,and the photocatalyst with an optimal Ag loading of 2% can degrade 88% of methylene blue within two hours.Furthermore,the PS microsphere template method was used to prepare N-TiO₂ hollow spheres,which were obtained by morphology and phase characterization.A p H of 11 and a calcination temperature of 500℃ are the best experimental parameters for preparing N-doped TiO₂ hollow spheres.The prepared N-TiO₂ hollow spheres can absorb visible light and can degrade 35% of methylene blue in two hours under visible light irradiation.Finally,the hollow N-TiO₂/CoAl-LDH composite material was prepared by the microwave hydrothermal method.The hollow N-TiO₂/CoAl-LDH composite material was characterized and tested,and it was found that the photocatalytic performance of the composite material was the best when the mass ratio between the N-doped hollow N-TiO₂ and CoAl-LDH was 1:4.According to the increase of the transient photocurrent intensity and the decrease of the impedance in the electrochemical test,it is concluded that the carriers in the composite material are effectively separated,and 74% of the methylene blue can be degraded in two hours under the irradiation of visible light.