Preparation And Properties Of Bi₂MoO₆ Based Composite Photocatalytic Materials

Bismuth molybdate(Bi2MoO6),which composed of alternating perovskite MoO42-and Bi2O22+layers,has the advantages of narrow band gap(2.4-2.8 eV),visible light absorption,high photochemical stability,controllable morphology,and nontoxicity.Due to its special layered structure and high stability,Bi2MoO6 has been widely studied as a photocatalyst in the fields of carbon dioxide reduction,pollutant degradation,and photocatalytic decomposition of water.However,the photocatalytic efficiency of Bi2MoO6 is difficult to be improved due to the rapid recombination of photogenerated electrons and holes.The photocatalytic performance of Bi2MoO6 is usually improved by methods such as morphology control and construction of heterojunctions.In this paper,Bi2MoO6 semiconductor is taken as the main research object,which is compounded with DUT-5 and UiO-66-NH2,respectively,and DUT-5/Bi2MoO6 and UiO-66-NH2/Bi2MoO6 are prepared by a simple solvothermal method.The photocatalytic degradation of tetracycline hydrochloride by DUT-5/Bi2MoO6 composite and rhodamine B by UiO-66-NH2/Bi2MoO6 composite were studied respectively,and the possible photocatalytic degradation mechanism was explored.The main research work is as follows:(1)The DUT-5/Bi2MoO6 composites were prepared by supporting DUT-5 on the surface of spherical Bi2MoO6 by secondary solvothermal method.The DUT-5/Bi2MoO6 composites were characterized by XRD,SEM and EDS.The photocatalytic reaction mechanism of type-I heterojunction is proposed by UV diffuse reflection,Mott-Schottky and active material trapping experiments.The photocatalytic reaction mechanism of type I heterojunction is proposed by UV diffuse reflection,Mott-Schottky and active material trapping experiments.When the content of DUT-5 was 15%,the composite had the best photocatalytic activity under visible light.After 60 min of visible light irradiation,the degradation efficiency of tetracycline by 15%DUT-5/Bi2MoO6 reached 84.22%.Its photocatalytic degradation rate constant is 2.12 times that of pure Bi2MoO6 and 5.37 times that of DUT-5 monomer.The enhanced photocatalytic activity is due to the fact that DUT-5 is embedded between Bi2MoO6 nanosheets,which promotes the flow of photogenerated electrons from DUT-5 to Bi2MoO6,thereby reducing the recombination rate of photogenerated electron-hole pairs.Through the BET test,the high specific surface area of DUT-5 can make the composite material have more active sites to fully contact with tetracycline,thereby improving its photocatalytic efficiency.(2)On the basis of the previous research results,the UiO-66-NH2/Bi2MoO6 composite material was prepared by the secondary solvothermal method again.The successful recombination of UiO-66-NH2 and Bi2MoO6 with different qualities was investigated by SEM and XRD.By degrading RhB under visible light,the effect of the amount of UiO-66-NH2 addition on the photocatalytic activity of the semiconductor was explored.By testing the UV absorption spectra of the photocatalytically degraded Rhodamine B solution at different times,it was found that the composite material had higher Rhodamine B degradation activity than pure Bi2MoO6.After 60 min of visible light irradiation,the degradation efficiency of 8%UiO-66-NH2/Bi2MoO6 on Rhodamine B reached 92.92%.Its photocatalytic degradation rate constant is 2.25 times that of pure Bi2MoO6 and 57.57 times that of UiO-66-NH2 monomer.Combined with radical trapping experiments,UV-Vis diffuse reflectance and Mott-Schottky results,a possible photocatalytic degradation mechanism is proposed to explore the reasons for the enhanced photocatalytic activity.