Preparation And Visible Photocatalytic Properties Of Porous TiO₂ Nanotube Arrays

Water environment pollution will cause a lot of harm,even threaten to the human survival and development.With the popularity of plastic products,Phthalic acid esters?PAEs?are widely used as plasticizers.Dibutyl phthalate?DBP?,the most representative plasticizers,is an endocrine disruptor widely found in the environment and difficult to biodegrade.Conventional water treatment method is difficult to remove DBP,and it poses a great threat to ecological balance and human health.In addition,the coexistence of organic pollutants and heavy metals has been found in major water system in China,forming combined pollution.Due to the great difference in physicochemical properties,it is difficult to remove pollutant simultaneously,which has become one of the water environment problems to be solved urgently.Photocatalytic technology can deeply oxidize the refractory organic pollutants in the water environment with the advantages of solar energy drive,deep reaction at room temperature,high degradation rate and no secondary pollution.At the same time,the heavy metals in the water environment reduced by photoproduction electron,can be reasonably used to promote the separation of photoproduction hole-electron pair.This can further improve the degradation efficiency of refractory organic pollutants and achieve the cooperative treatment of organic-heavy metal compound pollution.The application of semiconductor photocatalyst represented by TiO₂is restricted by the shortcomings of narrow light response range,low quantum efficiency,low mass transfer rate and difficult recovery of powder materials.Based on this,TiO₂ nanotube arrays with porous wall morphology were prepared,and doped with N or MoS₂in situ.The composite photocatalyst obtained not only broadens the light response range,but also promotes the separation of electron-hole pairs.Moreover,due to the special morphology and structure of the porous wall nanotube array,the utilization rate of sunlight and mass transfer are greatly enhanced to significantly improve the visible light catalytic activity.Nitrogen doped porous wall TiO₂ nanotube arrays?N@p-TNTAs?with visible light response were prepared by in-situ doping method using industrial titanium plates coated with Ti N metal ceramica.By means of SEM,TEM,XPS,XRD,N₂ adsorption/desorption,UV-vis and photocurrent,etc.,the morphology structure,composition and surface properties of the new material were analyzed.The results showed that the porous wall structure and N doping were formed successfully.The porous wall structure has excellent adsorption performance,and the successful doping of nitrogen element also makes it have visible light response,which all improve the photocatalytic performance of the new material.The photocatalytic activity of the new material was evaluated by catalytic oxidation of DBP in visible light,and the results showed that the photocatalytic efficiency of N@p-TNTAs was 3.7 times higher than that of unanodized?N/TiO₂?.In addition,the photocatalytic activity was still good after 6 times of cyclic experiments,which indicated that the structure of the new material was stable.MoS₂ sheet-insert doped porous wall TiO₂ nanotube arrays?MoS₂@p-TNTAs?were prepared by anodic oxidation and hydrothermal methods.Through a series of characterization and evaluation,the treatment of compound pollution in visible light was studied.The results show that the composite catalyst has strong visible light response,large specific surface area and high crystallinity,and the structure of porous wall nanotube arrays can still be maintained and the composition between semiconductors is compact after recombination.The composite photocatalyst showed excellent photocatalytic activity,structural stability and reusability.After20 cycles,DBP degradation was more than 85%,and the morphology of catalyst was stable.The synergistic treatment of compound pollution by composite catalyst has shown better efficiency than single pollution,the degradation kinetic constants of Cr?VI?and DBP were 8.3times and 3.3 times higher than that of single pollution.This is because Cr?VI?is reduced as the electron capture agent,and DBP is oxidized as the hole capture agent,realizing the full utilization of the electron-hole pair,so as to improve the photocatalytic reaction efficiency and realize the collaborative treatment of composite pollution.This provides a new idea for the preparation of novel visible TiO₂nanotube arrays.