Preparation And Photocatalytic Properties Of Silver-based/fluorene-based Composite Semiconductors

Semiconductor photocatalytic oxidation technology has extensive application prospect in the field of management of water pollution due to its high effience in utilizing sunlight to decompose different organic pollutants.Most of the tradational photocatalyst can only absorb UV-light due to their large band gap,which results in its low utilization of solar energy.Ag-based semiconductors possess excellent visible light response performance.But they easy suffer from poor stability due to the serious photochemical corrosion.On the other hand,Bi-based semiconductors have some advantages as photocatalysts,such as cheap,environmentally frirndly and the special layered structure of which benefits the separation of photoproduct electrons and holes.Thus in this dissertation,Ag-based semiconductor was coupled into the Bi-based semiconductor.Rhodamine B or Acid Orange II was selected as the degradation target molecule,the effect of loading different Ag-based semiconductor on the photocatalytic performance of Bi-based semiconductor were investigated.The main research contents are as following:First,BiVO₄ nanoplates were fabricated by the hydrothermal route.Then a series of Ag₂CO₃/BiVO₄ heterojunction composite photocatalyst were prepared through a simple precipitation method.The photocatalytic activity was tested under visible light irradiation in degradation of Rhodamine B.The results showed that the photocatalytic activity of the Ag₂CO₃/BiVO₄ heterojunction composite photocatalyst was obvious higher than the pure Ag₂CO₃ and BiVO₄.The band structure calculation showed that Ag₂CO₃ and BiVO₄ had a matching potential could form the heterojunction structure,which could efficient restrain the recombination of e-/h+ pairs,thus enhanced the photocatalytic activity of the sample.Second,BiOX?Cl,Br,I?microspheres assembled by BiOX nanoplates were prepared by solvothermal method.Then a series of Ag₂CO₃/BiOX?Cl,Br,I?heterojunction composite photocatalyst were prepared by a simple precipitation method.XRD,SEM,BET,UV-vis DRS were applied to characterize these prepared products,the effect of the samples were tested by the photocatalytic degradation of Acid Orange II.Results showed that the heterojunction composite photocatalysts performed extremely high photocatalytic activity.The band structure calculation showed that heterojunction structure between Ag₂CO₃ and BiOX?Cl,Br,I?can conform,whcih enhances the photocatalytic activity.Finally,the 1.5² ?m Bi₂WO₆ microspheres were prepared by hydrothermal method.Then Ag₂CO₃ and AgCl with different contents were deposited over Bi₂WO₆,producing heterostructured Ag₂CO₃/Bi₂WO₆ and AgCl/Bi₂WO₆ microspheres.Then the photocatalytic activity of the prepared catalysts was evaluated by photocatalytic degradation of rhodamine B under UV light and visible light irradiation.Results showed that the deposition of Ag₂CO₃ hardly enhanced the photocatalytic activity of the sample,but the AgCl/Bi₂WO₆ hetero-structured photocatalysts displayed significantly higher photocatalytic activity than that of pure AgCl and Bi₂WO₆ catalysts.So the main reason for the enhanced activity could be that the formation of AgCl/Bi₂WO₆ hetero-structures could effectively suppress the recombination of the photogenerated electron?e-?and hole?h+?,then increasing photocatalytic activity.