Photocatalytic Activity And Stabilitystudy On IVA And VB Silver-based Composite Oxides

The industrial development promotes that the new organic raw materials have been developed and applied. The pollutants contained in the discharged wastewater exhibit a complex diversity. Besides heavy metals, most pollutants are organics in the industrial wastewaters, which meet obstacle in their harmless treatment. The traditional biological, physical and chemical methods are unable to achieve the requirements of pollutant treatment. Therefore, it is increasingly important to solve the problem of environmental pollutions, especially for the water pollutions. In recent years, the photocatalytic technique using solar energy has caused much attention owing to its cheap, efficient, saving-energy and green et al. advantages, which can effectively degrade organic pollutants.The polyhedral short-rod Ag2CO3 photocatalyst is prepared by the ion exchange method, which has a universal degradation activity for Rh B, MO and MB organic dyes under the visible light. We reveal that Rh B, MO and MB dyes display the different degradation mechanism in the photocatalytic reaction by means of monochromatic wavelength irradiation method and radical capture experiments. The results show that superoxide radical, hydroxyl radical and hole play main roles in the Rh B, MO and MB degradation, respectively. The energy band and density of states of Ag2CO3 are calculated by DFT theory, indicating that Ag 5s orbit plays a dominant role in the conduction band and also takes place the hybrid effect of each other. It increases the effective mass of electrons, which is in favor of the transfer and separation of photogenerated electrons and holes to improve photocatalytic activity.Ag2CO3/Ag X(X=Cl, Br and I) heterojunction photocatalyst was achieved by modification of Ag X(X=Cl, Br and I) nanoparticles on the Ag2CO3 surface via two-step ion exchange method. It not only enhances the photocatalytic activity for degrading Rh B, MO and MB dyes but also improves stability compared with that of Ag2CO3. XPS analyses indicate that Ag X nanoparticles connect with the Ag2CO3 surface by chemical bonding effect, which avails the transfer and separation of charge carriers. The photoelectrochemical and PL properties demonstrate that Ag2CO3/Ag X(X=Cl, Br and I) heterojunction improves the separation efficiency of photogenerated electron-hole pairs. The monochromatic wavelength irradiation experiments reveal dye sensitization effect derives from Ag X rather than Ag2CO3. The transfer mechanism of charge carriers among Ag2CO3, Ag X, Rh B is discussed in detail.Ag2Nb(Ta)4O11 photocatalysts are prepared by the solid phase reaction method, which exhibits the universality for degrading Rh B, MO and MB dyes under the simulated sunlight. Meanwhile, the activity of Ag2Nb(Ta)4O11 photocatalysts shows no decreasing nearly after circle operations of degrading Rh B(MB) for 40(50) times, which indicates they have the superior stability. In addition, Ag2Ta4O11 also displays superior hydrogen production activity. It can realize the stable hydrogen production activity up to 5 days and still maintain hydrogen production activity after illumination of 30 days under the simulated sunlight. The used Ag2Nb(Ta)4O11 samples can realize the dual regeneration of photocatalyst and activity by the recalcination. The results from DFT theory demonstrate the valence band is mainly composed of Ag 4d and O 2p orbits, reducing bandgap. Highly overlapped Ag 4d and O 2p orbits suggest there is intense bonding effect existing in them, which plays an important role for the stability of photocatalyst. The layered structure of Ag2Nb(Ta)4O11 and the interlaced network structure of inner Nb(Ta)O6, Nb(Ta)O7 and Ag O6 polyhedrons in crystal can form transport channel of electron and hole in favor of separation of carriers. Ag atom in Ag O6 octahedron connects with six O atoms by the coordination bond, which avails improving stability of Ag2Nb(Ta)4O11 photocatalysts.Ag0.68V2O5 nanosheet and Ag0.68V2O5 hierarchical structure are prepared by means of introduction of the limited Ag+ ions into V2O5 using the hydrothermal method, respectively. The unique electronic structure results in the absorption edge extending to the infrared spectrum, reaching to 900 nm, which almost accounts for 60% of the solar spectrum. Integrating light absorption with electronic structure, V4+ ions with unique d1 electron configuration are produced after the limited Ag+ ions introduced into V2O5, which makes the Fermi level pass through the conduction band. The intense light absorption of Ag0.68V2O5 should come from electron transfer from conduction band to the higher empty band above conduction band. The ultrathin structure of Ag0.68V2O5 can improve transfer and separation efficiency of carriers at the direction perpendicular to nanosheet, enhancing photocatalytic activity. Serving as a photocatalyst, Ag0.68V2O5 can degrade MB and Rh B effectively.