Preparation And Photocatalytic Performance Of TiO₂ Nanotube Arrays

TiO2 nanomaterials prepared by anodic oxidation method have stable chemical properties,excellent photoelectrochemical properties,high photocatalytic activity,and large specific surface area,making them suitable for photocatalytic degradation,dye-sensitized solar cells,and gas-sensitive Sensors and other fields have a wide range of applications.In this paper,an anodic oxidation method was used to prepare a TiO2 nanotube arrays on a titanium sheet with titanium sheet as the titanium source,water as the oxygen source,ethylene glycol as the electrolyte solvent,and ammonium fluoride as the etchant.The effects of reaction time,reaction voltage,reaction temperature,ammonium fluoride concentration,and annealing temperature on the crystal structure,surface morphology,and related properties of TiO2 nanotube arrays were researched;and the doping of TiO2 nanotube arrays was investigated.The effect of modification on the photocatalytic and hydrophilic properties of the sample was investigated.The results of this paper show that:TiO2 nanotube arrays were successfully prepared on titanium sheets,and the generated nanotubes were uniform in size and arranged on the surface of the titanium sheet.The effects of different reaction conditions on the surface characteristics of TiO2 nanotube arrays were researched.As the reaction time increases,the crystal phase content of the anatase phase TiO2 increases.When the reaction time is 10h,the tube length and diameter of the nanotubes are about 50.5μm and 100nm,respectively.The chemical dissolution rate basically reached a dynamic equilibrium;when the reaction time exceeded 10h,the change in the crystal phase content and surface morphology of the nanotubes was small.With the increase of the reaction voltage,the diffraction peak intensity and tube length of the anatase phase TiO2 nanotubes increase first and then stabilize.The increase of the reaction voltage makes the electric field strength and reaction driving force increase,which is more conducive to nanotubes.When the reaction voltage exceeds 60V,the H+ concentration in the electrolyte is high,and the excessively high H+ concentration inhibits the progress of the nanotube generation reaction.Increasing the reaction voltage to hinder the growth of nanotubes.As the oxidation temperature increases,the driving force obtained by the reaction increases,the energy obtained by the atoms increases,and the growth rate of the nanotubes accelerates;when the reaction temperature is 25℃,the dissolution rate of the nanotubes accelerates,making the crystals of the anatase phase TiO2 Changes in phase content and morphology are no longer apparent.With the increase of the NH4F concentration,the crystal phase content of the anatase TiO2 nanotubes increases first and then decreases.When the NH4F concentration is low,the reaction rate is slow.With the increase of the NH4F concentration,the growth rate of the nanotubes is greatly accelerated;When the NH4F concentration exceeds 0.1mol/L,the generated nanotubes are rapidly dissolved,and the surface of the nanotubes is severely corroded.As the annealing temperature increases,the crystallinity of the anatase phase TiO2 increases.When the annealing temperature exceeds 500℃,the phase transition of the anatase phase TiO2 to the rutile phase TiO2 occurs.The TiO2 grains grow,and the tubular structure of the nanotubes is damaged.The prepared TiO2 nanotube arrays were tested for photocatalytic and hydrophilic properties.In the photocatalytic experiment,methyl orange was used as the degradation product,and the absorbance change of methyl orange was measured under high-pressure mercury lamp.The results showed that the photocatalytic degradation rate of methyl orange by TiO2 nanotube arrays was 94.1%;Under light irradiation,the hydrophilic property of TiO2 nanotube arrays was investigated by detecting the optical contact angle between the sample and water droplets.The results showed that the minimum optical contact angle between the sample and water droplets was only 5.8°.The rare-earth ion erbium was doped into the TiO2 nanotube arrays by the solution impregnation method,and the influence of the doped amount of the rare-earth ion erbium on the related performance of the TiO2 nanotube arrays was investigated.The experimental results show that the doping of europium ions has no significant effect on the crystal form and surface morphology of the TiO2 nanotube arrays,but it will affect the photocatalytic performance and hydrophilic properties of the sample.The number of ions substituted by Ti4+ is small,the number of-OH generated on the sample surface is small,and the number of photo-generated electron defects is limited;as the concentration of europium ions increases,the number of-OH generated on the sample surface increases,and the defect locations generated in TiO2 can be effectively Prevent photo-generated electron-hole recombination;but continue to increase the concentration of erbium ions,the doped ions become the photo-generated electron-hole recombination center,and excessive doping amount will cause the doped ions to form a new phase in TiO2.This is equivalent to introducing impurities.The photocatalytic degradation test and hydrophilic property test were performed on the prepared europium ion-doped TiO2 nanotube array.The results showed that when the europium ion concentration was 0.01mol/L,the photocatalytic degradation rate of TiO2 nanotube arrays to methyl orange was the highest.Up to 95.8%,the optical contact angle between the sample and water droplets is only 4.9°.