Controllable Synthesis And Photocatalytic Activity Of TipO₂/Ag-based Composites

For solving environmental pollution problems,especially in the field of organic pollutants degradation,photocatalysis technology has been widely investigated due to its high efficiency and rapidity.Efficient photocatalysts not only can be used to destroy bacteria,but also can degrade various organic pollutants in water and air.Among the various photocatalysts,TiO₂ has been regarded as a potential semiconductor photocatalytic material owing to its excellent stability,non-toxicity and low price.However,the application of TiO₂ in the field of photocatalysis has been greatly restrained due to its rapid recombination rate of photogenerated carriers and large band gap.Additionally,Ag based materials are becoming the promising candidate materials due to their excellent visible light response and stable photoelectric chemical properties.In this thesis,the macro/mesoporous TiO₂ and TiO₂nanofibers were prepared via the chemically induced self-assembly and electrostatic spinning routes,respectively,and then the macro/mesoporous TiO₂/Ag₂O,TiO₂/Ag₂O and TiO₂/Ag₃PO₄ nanofibers were synthesized by a chemical precipitation method.Finally,the photocatalytic performanceof the above composite materials for the degradation Rhodamine B?RhB?was investigated under visible light.The results are as follows:1.The macro/mesoporous TiO₂ was prepared by chemically induced self-assembly and high-temperature calcination method.Then,the macro/mesoporous TiO₂/Ag₂O heterojunction photocatalyst was successfully synthesized via a chemical precipitation route using AgNO₃ as precursor.Experimental results indicated that compared with the pure TiO₂,the light absorption range of macro/mesoporous TiO₂/Ag₂O composites is significantly increased.Moreover,the photocatalytic degradation performance was also greatly enhanced.Under optimal experimental condition?when the mass ratio of TiO₂ to Ag₂O was 1:2?,the as-prepared sample exhibited the best photocatalytic activity for RhB degradation.Additionally,the trapping experiment results revealed that the·O₂^-was the main active species in the degradation of RhB under visible light.The improved photocatalytic performance of TiO₂/Ag₂O composites can be ascribed to the fact that a p-n heterojunction is formed between Ag₂O and TiO₂,which greatly increases the separation efficiency of photogenerated carriers.Therefore,the photocatalytic activity of these composite materials can be improved.2.The TiO₂ nanofibers were prepared by the electrostatic spinning and high-temperature calcination methods.Then,the TiO₂/Ag₂O p-n heterojunction photocatalyst was successfully synthesized via a co-precipitation route.It was found that Ag₂O/TiO₂ nanofibers composites exhibited a higher photocatalytic performance than pure TiO₂ under visible light irradiation.Besides,the photocatalytic activity of Ag₂O/TiO₂ composites were obviously influenced by the addition content of Ag₂O,Ag₂O/TiO₂ nanofibers?40 wt%?exhibited the best activity for the degradation of RhB.Moreover,The apparent rate constants of Ag₂O/TiO₂nanofibers?40 wt%?were about2.1 times higher than that of pure Ag₂O.Additionally,the Ag₂O/TiO₂ nanofibers photocatalysts exhibited excellent stability.The enhanced photocatalytic activity can be ascribed to the following two reasons:Firstly,narrow band gap Ag₂O acted as a sensitizer to enhance the photoresponse of TiO₂ in the visible light region.Secondly,the p-n heterojunction was formed between TiO₂ and Ag₂O,which promoted the separation efficiency of the photogenerated charge carriers and improved the transfer rate of electrons.3.The TiO₂ nanofibers were prepared by the electrostatic spinning and high-temperature calcination methods,and then Ag₃PO₄/TiO₂ nanofibers heterojunction photocatalysts have been successfully synthesized via a chemical precipitation method.It was found that the absorption range of the obtained Ag₃PO₄/TiO₂ composites was extended to the visible region in comparison with that of pure TiO₂.Moreover,under optimal experimental conditions?when mass ratio of TiO₂ to Ag₃PO₄ was 10%?,the photocatalytic performance of the APTF10 composite was 2.6 times higher than that of pure TiO₂ nanofibers.Electrochemical performance test indicated that the APTF10 composite showed an enhanced photocurrent density and a smaller arc radius,resulting in a faster interfacial oxidation reaction of photogenerated holes.Additionally,the trapping experiment results indicated that the h⁺was the main active species in the degradation of RhB under visible light irradiation.