Synthesis And Photocatalytic Properties Of Bi₂WO₆ Matrix Composites With Three-dimensional Structure

Bismuth tungstate（Bi₂WO₆）has attracted extensive attention due to its unique layered structure and visible light response characteristics,but its photocatalytic activity is limited by high carrier recombination rate and narrow visible light response band.In this paper,the pure phase Bi₂WO₆was prepared by hydrothermal synthesis and solvothermal synthesis using Na₂WO₄·2H₂O and Bi（NO₃）₃·5H₂O as precursors and pure water and glycol as solvents respectively.On this basis,a series of Bi₂WO₆composite photocatalysts were prepared by adjusting the reaction conditions to control the micromorphology,heterojunction material composite and noble metal deposition in order to improve the photocatalytic activity and broaden the visible light response band of the catalyst.The catalysts were characterized by XRD,SEM,UV-Vis,BET and XPS.The performance of the catalyst was evaluated by electrochemical test,photocatalytic activity experiment and free radical capture experiment,and the mechanism of the catalyst was discussed.（1）The three-dimensional Bi₂WO₆/Bi OBr composite with controllable morphology was prepared by hydrothermal method using cetyltrimethyl ammonium bromide（CTAB）and didodecyldimethyl ammonium bromide（DDAB）as templates and bromine sources.The photocatalytic degradation of azo dyes,rhodamine B（Rh B）,methylene blue（MB）,malachite green（MG）and methyl orange（MO）,showed that the best photocatalytic performance was obtained when the mass ratio of DDAB/CTAB was 2.6/1.The UV-vis diffuse reflection curve proves that the response range of Bi₂WO₆/Bi OBr is wider than that of pure Bi₂WO₆.The photocatalytic mechanism of Bi₂WO₆/Bi OBr was analyzed based on band matching principle,active species capture experiment and Mulliken atomic electronegativity theory.（2）The three-dimensional Bi₂WO₆/Bi OCl composite with controllable morphology was prepared by solvothermal method with ethylene glycol as solvent,CTAB or DDAB as template,Na Cl as auxiliary agent and chlorine source.The transformation from 500 nm block material to 4μm hollow microspheres to 2-3μm flower-like microspheres was realized by regulating the amount of Na Cl.The photocatalytic degradation of azo dyes showed that the best photocatalytic performance was obtained when the mass ratio of Na Cl/CTAB was 0.5/1.The UV-vis diffuse reflection curve shows that the visible light response band of the material is broadened to 650 nm.The photocatalytic mechanism of Bi₂WO₆/Bi OCl and Bi₂WO₆/Bi OBr was differentiated by active species capture experiment.（3）Based on Bi₂WO₆/Bi OBr composite,the noble metal gold（Au）nanoparticles were uniformly loaded on Bi₂WO₆/Bi OBr by hydrothermal reduction deposition method.Through photocatalytic degradation of Rh B,it was proved that the heterojunction and noble metal plasma resonance（SPR）effect had the best synergistic effect and the best photocatalytic performance under the condition of 1.5%Au content.UV-visible diffuse reflection curves show that the absorption edge of the material is widened to 650-750 nm.