Preparation Of Ag₃PO₄/MoO₃/TiO₂ Composite Electrode And Study On Its Photoelectrocatalysis Properties

The Photocatalytic method as a green chemical technology used for degradation of refractory persistent organic pollutants in the environment has become a research topic.TiO₂ as the most representatively and practical prospects photocatalyst, especially TiO₂ nanotube arrays attracted great attention from researchers because of its ordered structure,high specific surface area and better charge transfer performance. However, its excitation wavelength is less than the 387 nm ultraviolet light. The utilization of visible light accounting for most of the solar spectrum is low. In addition, the photo-generated charge and holes of TiO₂ are easy to recombine within the crystal, which lead to the low quantum efficiency. These two problems restrict the application of TiO₂ in practice.A series of TiO₂ nanotube arrays were synthesized in order to solve these problems.Then, they were modified by the semiconductor compound method, in the aim of dramatically improveing TiO₂ utilization ratio of visible light, quantum efficiency and photocatalytic properties, providing basic support for the practical application of TiO₂.The main research contents and results are as follows:?1?A series of TiO₂ nanotube array electrodes were successfully synthesized with different water content, voltage rise rate and reaction time by the anodic oxidation method on Ti foil in C2H6O2/NH4F/H2 O electrolyte. The structure and optical properties of the TiO₂ nanotube array electrodes were characterized by SEM, XRD and electrochemical techniques.The photocatalytic activity of the TiO₂ nanotube array electrode was evaluated by degrading MB in aqueous solution. The results showed that the TiO₂ nanotube array electrode, which was prepared by 2%?v/v? H2 O electrolyte and 60 V DC voltage with an increasing rate of0.1 V·s-1, exhibited a distinguishable orderly array structure and higher quantum efficiency and presented a positive catalytic effect on removing methylene blue?MB? from the aqueous solution, the photoelectrocatalytic degradation efficiency of MB can reach 25% after 120 min of reaction.?2?The MoO₃/TiO₂ nanotube arrays electrode was prepared by anodic oxidation method combined with the hydrothermal technique. The coverage of MoO₃ nanoparticles in TiO₂ nanotubes can be tuned by changing the hydrothermal reaction time. Electrochemical test results showed that under visible light irradiation, the MoO₃/TiO₂ nanotube array electrode showed an obvious photocurrent response and its charge transfer rate hasimproved significantly. When hydrothermal reaction time was 6 h. In the same experimental conditions, the methylene blue photoelectrocatalytic degradation efficiency of MoO₃/TiO₂ has a significant improvement under simulated sunlight irradiation when compared with pure TiO₂ nanotube arrays electrodes, the activity of MoO₃/TiO₂ nanotube array electrodes displayed 1.42 times as high as that of pure TiO₂ nanotube array electrode.?3?A new composite electrode of Ag₃PO₄/MoO₃/TiO₂ was fabricated by anodic oxidation combined with chemical impregnation and hydrothermal technique. The clusters of Ag3PO4/MoO₃ nanoparticles formed on the surface of the TiO₂ nanotubes and has no damage to their original ordered array structure and the phenomenon of blocking did not happen. Besides that, the visible light absorption ability of Ag₃PO₄/MoO₃/TiO₂ nanotube array electrodes was significantly enhanced and has higher photocurrent response than the pure TiO₂ nanotube array electrodes. The degradation efficiency of sulfathiazole?ST?reached 98.9% after 120 min of photoelectrocatalytic degradation under the condition of simulated sunlight irradiation. Under the same degradation condition, the ST degradation rate of pure TiO₂ nanotube array electrode and MoO₃/TiO₂ nanotube array electrode was31.8% and 71.75%. The efficiency of photoelectrocatalytic degradation of ST of the parepared Ag₃PO₄/MoO₃/TiO₂ composite electrode increased 3.11 times and 1.38 times,respectively. Moreover, the reactive oxygen species were ·OH and holes during the photocatalytic reaction, which was detected by radical complexation experiments. After five times catalytic degradation experiment, the photoelectriccatalytic degradation ability of Ag₃PO₄/MoO₃/TiO₂ composite electrodes has no abvious decline. The results showed that the catalyst has good stability and reusability.