Study On The Preparation And Photocatalytic Properties Of Titanate Nanotube Arrays Composite Meterials

Nanotube arrays have drawn extraordinary attention due to their highly ordered tube structure and high specific surface area. The tubular structure is easy to synthesize nanotube composite materials, which can improve photocatalytic activities of catalysts significantly. BaTiO3 and SrTiO3 nanotubes array were prepared by combining of anodic oxidation and hydrothermal method, and then metal Ag or Ou2O was assembled to titanate nanotube arrays. The morphologies, structures and compositions of catalysts were characterized by SEM, EDS, XRD and XPS analysis. And the photocatalytic activities of catalysts were tested by photocatalytic degradation of methyl orange and photocatalytic hydrogen evolution from water.Firstly, TiO2 nanotube arrays were prepared by the anodization of metallic Ti foil in different electrolytes. Then BaTiO3 and SrTiO3 nanotube arrays were synthesized by hydrothermal method. Among them, the samples maintained good morphology which were obtained by hydrothermal treatment of TiO2 templates at 150℃for 2 h, the TiO2 nanotube arrays were prepared in glycol/HiO based electrolyte. SEM analysis shows that nanotube arrays have regular morphology and uniform diameter. EDS analysis shows that the element contents of Ba and Sr are all higher. Moreover, XRD analysis shows that cubic crystal BaTiO3 and SrTiO3 nanotube arrays were formed by hydrothermal method.In order to improve the photocatalytic activities of BaTiO3 and SrTiO3 nanotube arrays, the Ag/BaTiO3 and Ag/SrTiO3 nanotube arrays were obtained by immersion-illumination method. SEM analysis shows that Ag nanoparticles are uniformly dispersed on the nanotubes, this is consistent with the result of XRD analysis. Moreover, XPS analysis exhibits that Ag nanoparticles exist in a form of metallic silver.Then the photocatalytic performances of Ag/BaTiO3 and Ag/SrTiO3 nanotube arrays were studied by photocatalytic degradation of methyl orange and photocatalytic hydrogen evolution from water. In the test of photocatalytic degradation of methyl orange, the effect of different pH values on photocatalytic performance was studied. The result shows that Ag/BaTiO3 and Ag/SrTiO3 nanotube arrays exhibit eximious photocatalytic activity at pH=3. In the test of photocatalytic hydrogen evolution from water, the effect of AgNO3 concentration on photocatalytic performance was studied. The result shows that Ag/BaTiO3 and Ag/SrTiO3 nanotube arrays obtained in 0.7 M AgNO3 have higher hydrogen production rate. The hydrogen production rate of Ag/BaTiO3 nanotube arrays and Ag/SrTiO3 nanotube arrays was 1.675 mmol/m2/h and 6.614 mmol/m2/h, respectively. The loading of Ag improves the photocatalytic activity of catalyst. This is due to that metallic Ag accelerates the separation of electrons and holes as a photoelectron capture detector, so the quantum efficiency of catalyst is improved.In addition, the Cu2O/SrTiO3 nanotube arrays were prepared by immersion-illumination method. The SEM and EDS analysis show the amount and size of Cu2O deposited on the nanotube arrays increases with increasing of Cu(NO3)2 concentration. Moreover, XRD analysis shows that CU2O is cubic crystal. In the test of photocatalytic hydrogen evolution from water, the effect of Cu(NO3)2 concentration on photocatalytic performance was studied. The hydrogen production rate of Cu2O/SrTiO3 nanotube arrays obtained in 0.005 M Cu(NO3)2 was 76.584 mmol/m2/h, so the photocatalytic activity was improved significantly. The result shows that the coupling of Ou2O with SrTiO3 nanotube arrays promotes the transfer of photoelectrons. It not only extends the spectral response range of SrTiO3, but also reduces the combination of photogelectrons and holes, so the photocatalytic activity of photocatalyst was improved significantly.