Study On Preparation And Photocatalytic Properties Of Silver-Based Composite Photocatalyst

With the progress of science and technology and the development of industry,environmental pollution,especially water pollution,is becoming more and more serious,which not only destroys the stability of ecosystem,but also directly harms human health.The traditional water decontamination technology has many deficiencies.Semiconductor photocatalysis technology,driven by solar energy,can degrade organic pollutants thoroughly,and solve energy crisis and water pollution at the same time.Among all the semiconductor photocatalysts,silver based photocatalysts have attracted wide attention due to their high catalytic activity under visible light illumination.However,silver based semiconductors have some disadvantages,such as high cost and poor cycle stability,which limits their further application.To solve above problems,we have respectively taken Ag₂MoO₄ and Ag₂WO₄ as research objects,and two kinds of silver based composite systems,namely Ag₂MoO₄/WO₃·0.33H₂O and Ag₂WO₄/g-C₃N₄ nanotubes,were constructed and discussed.The influences of some process parameters such as the ratio of raw materials in the final composties were explored.The internal relationship between the microstructure of the photocatalysts and their photocatalytic efficiency was mainly analysized.The composites with obviously enhanced photocatalytic performance were obtained.In addition,the cooperative photocatalysis mechanism under the visible light irradiation was preliminarily clarified.This work mainly includes the following two aspects:?1?Study on the structure and properties of Ag₂MoO₄/WO₃·0.33H₂O composite photocatalysts.The Ag₂MoO₄/WO₃·0.33H₂O composite was synthesized by in-situ method.Rhodamine B?Rh B?solution and levofloxacin?LVFX?solution were used to assessed the photocatalytic properties of photocatalysts,and the synergistic photocatalytic mechanism of the as-prepared hybrids was also analyzed.The experimental results show that when the theoretical molar ratio of WO₃·0.33H₂O to AgNO₃ is 1:0.15,the as-developed hybrid has the highest photocatalytic efficiency,which is 99.0%in 45 min for Rh B and 40.9%in 120 min for LVFX.The proper reason for this improvement is that there are chemical bonds between WO₃·0.33H₂O and Ag₂MoO₄.Moroever,superoxide radicals play a leading role and holes play an auxiliary role during the process of photocatalytic degradation.?2?Study on the structure and properties of Ag₂WO₄/g-C₃N₄ NTs composite photocatalysts.The Ag₂WO₄/g-C₃N₄ NTs composite photocatalyst was prepared via an in-situ composite strategy.The photocatalytic performance of the samples was discussed by the degradation of Rh B under visible light,and the catalytic mechanism was also analyzed.The characterization results show that the photocatalytic efficiency of the as-prepared Ag₂WO₄/g-C₃N₄ NTs composite increases firstly and then decreases along with the increase of the Ag₂WO₄.When the feed ratio of g-C₃N₄NTs:Ag₂WO₄ reaches 3:2,the photocatalytic degradation efficiency achieves the optimal value,that is 92.4%within 20 min,which obviously exceeds 2.8%of pure g-C₃N₄ NTs and 38.9%of pure Ag₂WO₄ within the same time frame.Moreover,the separation and migration efficiency of photoelectron-hole pairs of the composites can be accelerated in comparison with pure samples.In addition,superoxide radicals and hydroxyl radicals play major roles in the photocatalytic degradation process.