Preparation And Optimization Of Bi₂O₂CO₃/Bi₂WO₆ Composite Photocatalyst

Photocatalysis technology owning the advantages of low cost,high security,high efficiency,controllability,expansibility and the potential to develop solar energy has received a lot of attention.In the early stage,it mainly focused on the study of TiO₂,but the wide band width of TiO₂ led to a narrow range of light response and low utilization of solar energy.Therefore,some organic polymer and olymetallic oxide semiconductor with smaller band width show the characteristics of the visible light response,and gradually become the popular choice of photocatalyst.Bismuth compounds were selected as the object of our study.Because of unique outer electron configuration?6s²?,bismuth has a relatively narrow bang gap and good visible light absorption capacity,so it has become a high regarded photocatalyst.With the study of single bismuth compounds,the researchers graduly found their some disadvantages,such as specific surface area was small,carriers were easy to recombine,they were easy to influence its photocatalytic activity.In recent years,bismuth photocatalyst mainly focuses on the optimization of its structure,such as metal ion doping and semiconductor composite.This paper selected Bi system photocatalyst bismuth tungstate?Bi₂WO₆?and oxygen bismuth carbonate?Bi₂O₂CO₃?as the research object,prepared Bi₂O₂CO₃/Bi₂WO₆ composite photocatalyst.The details of this article are as follows:We prepared Bi₂O₂CO₃/Bi₂WO₆ composite photocatalyst by two-step hydrothermal method.In the first step,we prepared Bi₂O₃ by hydrothermal method with bismuth nitrate and ethylene glycol as precursor reactants.After using bismuth oxide and ethylene glycol as Bi₂O₂CO₃ precursor reactant,sodium tungstate and bismuth nitrate as Bi₂WO₆ precursor reactants,then mixed them and proceeded a high temperature high pressure reaction to get Bi₂O₂CO₃/Bi₂WO₆ composite material.Then we discussed the formation mechanism of Bi₂O₂CO₃.Based on it,we replaced precursor Bi₂O₃ with Ag loaded Bi₂O₃.Because Ag catalyzed ethylene glycol in the reaction,more carbonate was produced.So that we could improve the content of Bi₂O₂CO₃ in the final composite.It was obtained by the characterization methods such as XRD,SEM,PL,Bi₂O₂CO₃/Bi₂WO₆ accessed larger surface area and lower carriers recombination rate than pure Bi₂WO₆ and pure Bi₂O₃.At the same time,using Ag loaded Bi₂O₃ as precursor increased the Bi₂O₂CO₃ content in the final product,improved Bi₂O₂CO₃/Bi₂WO₆ composite phptocatalyst heterojunction structure.In the photocatalytic degradation experiment,it also showed higher activity.Finally,the conclusion was obtained by photocatalytic degradation experiment.The photocatalytic activity of Bi₂O₂CO₃/Bi₂WO₆ composite was the best when the capacity of Ag particle?AgNO₃?was 3wt%,it was about 2.05,3.41and 10.19 times than that of Bi₂O₂CO₃/Bi₂WO₆,pure Bi₂O₃ and pure Bi₂WO₆,respectively.The stability of the catalyst was studied by repeated five photocatalytic degradation experiments on the same sample.On the basis of the successful preparation of Bi₂O₂CO₃/Bi₂WO₆ composite photocatalyst,the Ag particle was loaded on the surface of Bi₂O₂CO₃/Bi₂WO₆composite photocatalyst by photodeposition.SEM-EDS and SEM-Mapping test confirmed the existence of Ag particles on the surface of composite materials.Through the PL test,it was shown that the Ag particles in the system reduced the recombination of the carrier in the reaction process.Finally,in order to study the effect of Ag particle on photocatalytic activity on the surface of composite materials,the gas phase degradation isopropanol was used to test all samples.The results showed that the photocatalytic activity of Bi₂O₂CO₃/Bi₂WO₆ was significantly enhanced after the surface loading of Ag particles.When the capacity of Ag particle?AgNO₃?was 7wt%,the activity was 8.34 times that of the unloaded Ag particle Bi₂O₂CO₃/Bi₂WO₆ sample.The stability of the catalyst was studied by repeated five photocatalytic degradation experiments on the same sample.