Preparation Of Two-dimensional Supported Nanocomposite Photocatalytic Materials And Their Visible-light Driven Photocatalytic Properties

With the development of science and technology,the environmental problems brought by the acceleration of industrial production have been increasingly attracted extensive attention of the whole society.Among them,the industrial wastewater containing a lot of toxic,highly stable,difficult to biodegradable harmful substances,has brought great harm to the health and environment.Because of the advantages of simple operation,mild reaction conditions,low energy consumption and less secondary pollution,the semiconductor photocatalytic oxidation technology has been widely concerned in the field of environmental protection.Photocatalytic technology as a kind of technology which effectively using the light energy to treat water pollution has important application prospect in the field of environment.However,at present,photocatalytic technology faced two main problems that the absorption of photocatalytic materials to visible light is limited and photogenerated electron and hole are easy to be combined.According to a lot of experiments,compared with single-component photocatalysts,the multi-component photocatalysts display better photocatalytic activity in degrading organic pollutants.The main reason is that the band gap structures of the composite photocatalyst materials are matched,so that they can effectively constrain the combination of photogenerated electrons and holes at the same time,thus enhancing their absorption of solar light in the visible region.Based on the above research background,we choose for two-dimensional supported nanocomposite photocatalytic materials as our research objects,in order to improve the photo generated electron-hole separation.The following research works have been carried out in this thesis.1.BiOCl nanoplates which contain a lot of oxygen vacancies were synthesized using mannitol by hydrothermal synthesis method.Then Bi₂S₃/BiOCl nanocomposite was prepared using thioacetamide?TAA?through the ion-exchange method.According to the results of photocatalytic activity experiments under visible light irradiation,when the mass ratio of TAA to BiOCI is 28.8%,the B1₂S₃/BiOCl composite showed the best photocatalytic activity,which is 2.5 and 16 times higher than BiOCl and Bi₂S₃,respectively.At the same time,according to trapping experiments,the main active species in the process of photocatalytic are ·O₂-and h+,but ·OH also has a certain influence.Moreover,a possible reaction mechanism was proposed.2.Bulk g-C₃N₄ was synthesized by a facile calcination method in a muffle furnace.The ground g-C₃N₄ was calcined again to obtain the exfoliated g-C₃N₄.A series of g-C₃N₄/BiOCl composite photocatalysts were prepared by a precipitation method.According to the results of photocatalytic activity experiments under visible light irradiation,3%g-C₃N₄/BiOCl composite photocatalysts showed the best photocatalytic activity.Then,the Bi₂S₃/g-C₃N₄/BiOCl composite photocatalysts were prepared by ion exchange method.The effect of different ion exchange time on photocatalytic degradation of rhodamine B under visible light irradiation was explored.When the ion exchange time was 0.5 h,the Bi₂S₃/g-C₃N₄/BiOCl composite showed the best photocatalytic activity,which is 2 and 13 times higher than BiOCl and g-C₃N₄,respectively.The increased photocatalytic efficiency can be attributed to the matched band gap structures of g-C₃N₄ and BiOCl,which benefits the separation of photogenerated electronic and hole.Moreover,by the simple ion exchange method generating Bi₂S₃ on BiOCl surface,greatly improve the interfacial charge transfer effectively.At the same time,according to the trapping experiments,the active species in the process of photocatalytic are ·O₂-and h+.Moreover,a possible reaction mechanism was proposed.3.First,TiO₂ nanoplates were prepared by a hydrothermal method using HF as the structure director.Then ZnIn2S4/TiO₂ nanocomposites were fabricated using low-temperature and one-step method.According to the results of photocatalytic activity experiments under visible light irradiation,TiO₂/ZnIn2S4?1:1?nanocomposite showed the best photocatalytic activity,which is 3.8 times higher than ZnIn2S4.TiO₂/ZnIn2S4 nanocomposite can not only broaden the absorption of TiO₂,but also inhibit the combination of photogenerated electrons and holes.