Preparation Of Bi₂MoO₆-based Photocatalytic Materials And Study On Their Photocatalytic Performance

Photocatalysis is known as a promising route to treat pollutants in water,which is an environmentally friendly approach and has the high energy efficiency.The key part of the photocatalytic technology is the photocatalytic materials used in the reaction process.Among these photocatalytic materials,semiconductor materials are usually used photocatalyst.However,the traditional semiconductor photocatalysis can only absorb UV light?about 4%of solar energy?,this seriously restricts the practical applications of semiconductor photocatalysis.It is of great importance to explore a novel semiconductor photocatalysis working under visible light?about 45%of solar energy?.Bi₂MoO₆,as a simplest Aurivillius phase containing perovskite layers?Bi₂O₂?(A_m-1B_mO_3m+1),is a promising visible light driven and efficient photocatalyst.The paper has primarily studied Bi₂MoO₆ and Bi₂MoO₆-based composites synthesized by one-step hydrothermal method,situ growth method and high temperature solid phase method.As-prepared samples are applied in the degradation of organic pollutants,and analyzed the relationship between structure and performance through a series of characterization.The details are listed as follows:?1?Bi₂MoO₆,Ag₃PO₄ and Ag₃PO₄-Bi₂MoO₆ samples were prepared via one-step hydrothermal method and situ growth method.The results showed that the Ag₃PO₄nanoparticles had uniformly grown in the surface of Bi₂MoO₆ hierarchical hollow spheres.And,in comparison pure Bi₂MoO₆,Ag₃PO₄-Bi₂MoO₆ had a distinctly enhanced absorption in the visible region.More than that,when the hydrogen peroxide?H₂O₂?was introduced in the process of photocatalytic degradation,the photocorrosion of Ag₃PO₄ was greatly inhibited and the stability was observably improved by capturing the photo-induced electrons of Ag₃PO₄ surface.Furthermore,Ag₃PO₄-Bi₂MoO₆ also showed outstanding photocatalytic performance the due to the protection and promotion effect of hydrogen peroxide?H₂O₂?.The reaction rate constant of 15 wt%Ag₃PO₄-Bi₂MoO₆-H₂O₂(k=0.03585 min^-1)was 9.50 times of the individual Bi₂MoO₆(k=0.00378 min^-1).Meanwhile,the Ag₃PO₄-Bi₂MoO₆ samples had good stability during photocatalytic degradation.?2?MgFe₂O₄ was synthesized by one-step hydrothermal method,impregnation method,room temperature solid phase method and the high temperature solid phase method,respectively.X-ray powder diffraction?XRD?technique was used to examine the phase purity and crystallographic structure of the prepared MgFe₂O₄.The result was that the pure phase MgFe₂O₄ has only been prepared by the high temperature solid phase method.The citric acid was added in the solution as surfactant by an equal molar ratio of total metal nitrates to citric acid.?3?Bi₂MoO₆,MgFe₂O₄ and MgFe₂O₄-Bi₂MoO₆ samples were prepared via one-step hydrothermal method and high temperature solid phase method.The results of UV–vis absorption spectra indicated that MgFe₂O₄-Bi₂MoO₆ had a higher visible light absorption intensity than individual Bi₂MoO₆,which broaden the response range of Bi₂MoO₆ towards light.At the same time,the photocatalytic performance of samples was analyzed by the degradation of the malachite green?MG?aqueous solution.The results showed that MgFe₂O₄exhibited dramatic adsorption for MG molecules which came from the high specific surface area.Compared with Bi₂MoO₆,all MgFe₂O₄-Bi₂MoO₆ composites exhibited higher photocatalytic activities and the reaction rate constant of 20 wt%MgFe₂O₄-Bi₂MoO₆(k=0.0113 min^-1)was 8.70 times of the individual Bi₂MoO₆(k=0.0014 min^-1).The active species trapping experiments indicated that h⁺and·O₂^–played important roles during the photocatalytic degradation process.