Preparation And Photocatalytic Properties Of Bi₂MoO₆-based Composite Nanomaterials

Bi₂MoO₆ based semiconductor nanomaterials have attracted extensive attention in the field of catalysis due to their excellent electronic structure,unique physical and chemical properties.Aiming at the problems of wide band gap of Bi₂MoO₆ and short recombination time of photogenerated carriers,this thesis uses the controllable liquid phase synthesis method and the effects of morphology,metal doping and heterostructure on the band gap,redox capacity and carrier separation efficiency of Bi₂MoO₆ were studied.The essential relationship between the corresponding energy band and electronic structure and the catalytic performance of Bi₂MoO₆ was discussed,and the nature of catalytic reaction was deeply studied,which provided theoretical basis and data support for the development of new efficient catalysts.The specific work of this paper is as follows:(1)The Bi₂MoO₆ nanomaterials with different morphologies were prepared by the method of hydrothermal synthesis by adjusting the type of solvent.The crystal plane position and optical band gap of Bi₂MoO₆ nanomaterials with different morphologies have been studied.It is found that compared with Bi₂MoO₆ flower-like nanosheets,the photogenerated carrier separation efficiency and light absorption range of Bi₂MoO₆bulk nanosheets are significantly improved,and they have stronger photocatalytic efficient.(2)Visible light responsive Bi₂MoO₆/CuO photocatalyst was prepared by hydrothermal method.The crystal structure,chemical state,atomic composition,optical property and morphology of Bi₂MoO₆/CuO were studied in detail.In comparison with pristine Bi₂MoO₆ and CuO,the obtained Bi₂MoO₆/CuO composite shows a significant photocatalytic degradation of Rhodamine B under visible-light irradiation,proving that the combination of Bi₂MoO₆ and CuO might not only increase absorption of visible light,but also promote the separation efficiency of photogenerated electrons and holes.Density functional theory calculation,UV-vis DRS spectra and Mott-Schottky analysis were used to elucidate the electronic properties and band structures,showing that the valence band(VB)and conduction band(CB)positions of Bi₂MoO₆ and CuO matched well to form the staggered band structure with Z-scheme charge transfer.The possible formation mechanism of Z-scheme heterostructure and photocatalytic mechanism of Bi₂MoO₆/CuO composites were proposed.This work provides a simple route to synthesize visible light photocatalysts Z-scheme heterostructure for degradation of dyes in water.(3)The visible light-responsive Pd@Bi₂MoO₆ photocatalyst was prepared by in-situ photoreduction method,and the crystal structure,chemical composition,optical properties and morphology of Pd load Bi₂MoO₆ were systematically studied.Compared with Bi₂MoO₆ alone,it is found that Pd load Bi₂MoO₆ nanosheets exhibit enhanced photocatalytic activity under visible light irradiation.This proves that the loaded Pd nanoparticles can be used as the electron trap of the composite material,which enhances the separation efficiency of photogenerated carriers.At the same time,Pd metal produces a plasmon resonance effect under visible light,and the generated photogenerated electrons flow to the conduction band of Bi₂MoO₆,further promoting the separation of carriers.Due to the synergistic effect of Pd metal nanoparticles and Bi₂MoO₆,when the doping mass of Pd nanoparticles was 10%,the degradation rate of the catalyst to the dye reaches 99%.