Modification Of TiO₂ Nanotube Array On Titanium Mesh Surface And Study On Photocatalytic Performance

TiO₂ nanotube arrays have received extensive attention due to their high orientation,large specific surface area,and uniform interface structure.Compared with nanoparticles,the vertical alignment structure of TiO₂ nanotube arrays can provide direct electron diffusion pathways at the interface,which greatly improves energy conversion efficiency.In this paper,anodizing method is used to prepare TiO₂ nanotube arrays on the surface of titanium mesh,combined with heat treatment and semiconductor compounding methods to modify the TiO₂ nanotube arrays,expand the spectral response range of the TiO₂ nanotube arrays,increase the carrier transmission rate and reduce photogeneration The electron-hole recombination rate.SEM,TEM,XRD,Raman and XPS were used to characterize the surface morphology,crystal structure and composition of TiO₂ nanotube arrays.Use UV-Vis DRS,PL,photocurrent test to investigate the optical and photoelectric properties of the TiO₂ nanotube array.Rhodamine B was used as the target pollutant to evaluate its photocatalytic activity and explore its photocatalytic mechanism.The main progress and results are as follows:TiO₂ nanotube arrays were constructed on the surface of titanium mesh by anodizing method,and the effects of anodizing voltage and time on the surface morphology,crystal structure and photocatalytic properties of TiO₂ nanotube arrays were studied.The anodizing voltage was increased from 5 V to 30 V,and the TiO₂ structure changed from nanopores to nanotubes and finally to nanotube rupture.As the voltage increases,the inner diameter and wall thickness of the nanotubes increase,and the length first increases rapidly and then decreases slightly.Photocatalytic degradation experiments show that the TiO₂ nanotube array prepared by15 V voltage is the best.The anodic oxidation time was changed at 15 V,and the morphology of the TiO₂ nanotube array did not change significantly with the time from 20 min to 100 min.The photocatalysis experiment shows that the TiO₂ nanotube array prepared in 40 min has the best effect.The TiO₂ nanotube arrays prepared with different experimental parameters are all amorphous,indicating that the experimental parameters have no effect on the crystal structure.In order to improve the photocatalytic activity of the amorphous TiO₂ nanotube array,heat treatment is used to modify it.As the heat treatment temperature increases from 300℃to700℃,the inner diameter gradually decreases,and the wall thickness increases until it ruptures,and the length does not change significantly.As the temperature increases,TiO₂ nanotubes transform from amorphous to anatase phase and from anatase phase to rutile phase.TiO₂nanotubes heat-treated at 600℃are a mixed crystal phase of anatase and rutile.After changing the crystal structure,the response of TiO₂ nanotubes to visible light is enhanced,which improves the transmission rate of photogenerated carriers and reduces the recombination rate.After heat treatment,the photocatalytic efficiency of the TiO₂ nanotube array is improved,and the photocatalytic activity of the TiO₂ nanotube array is the highest when heat-treated at 600℃.In the photocatalytic process,h⁺and·OH are the main active species,which play a major role in the photocatalytic process.In order to further improve the photocatalytic activity of TiO₂ nanotube arrays,the g-C₃N₄/TiO₂ nanotube array（CN/TNTs）composite material was prepared by a combination of anodic oxidation and co-calcination.After the composite,the morphology of the TiO₂ nanotube array did not change significantly,the surface has been composited with lamellar g-C₃N₄,and the composite amount increased with the increase of raw materials.After g-C₃N₄ recombination,the absorption band edge of the TiO₂ nanotube array is significantly red-shifted.The photogenerated carriers reduce the recombination rate of electron-hole pairs through the Z-scheme transfer mechanism,which greatly increases the carrier transmission rate.The photocatalytic efficiency of the TiO₂ nanotube array was significantly improved after the composite,and the 2.0 g CN/TNTs composite material had the highest photocatalytic activity.In the photocatalytic process,·O₂^-,h⁺and·OH will work together to degrade Rhodamine B.Mo S₂ was compounded on the surface of the TiO₂ nanotube array by combining magnetron sputtering and heat treatment.The results show that TiO₂ and Mo S₂ are anatase phase and 2H phase,respectively.After compounding,the wall thickness of the TiO₂ nanotube array gradually increases until the nanotubes are completely covered.After 2H phase Mo S₂ composite,the light response range of TiO₂ nanotube array increases,and the absorption band edge is red-shifted.By constructing a Z-scheme transfer mechanism,the transmission rate of photogenerated carriers is increased and the recombination rate is reduced.After Mo S₂ composite,the photocatalytic activity is significantly improved,and the Mo S₂/TiO₂ nanotube array composite material with 7 min magnetron sputtering has the highest catalytic degradation rate.In the photocatalytic process,·O₂^-and·OH are the main active species in the catalytic process,while h⁺plays a smaller role.