Bi-based Solid Solutions Bi₂WxMo_1-xO₆/g-C₃N₄ For Photocatalytic Removal Of Indoor Formaldehyde

With the diversified development of interior decoration contents,indoor environmental pollution caused by decoration materials has attracted people’s attention.As one of the main indoor environmental pollutants,formaldehyde has the characteristics of low concentration and continuous release.Living in the environment exceeding the limit value of formaldehyde for a long time will cause great harm to human body.The green and mild photocatalytic technology is suitable for the treatment of gaseous pollutants at low concentrations.Therefore,photocatalysis technology has become the most promising technical means to remove indoor formaldehyde.However,the effect of a single type of photocatalyst in practical application is not ideal,because of the high recombination rate of photogenerated electron-hole pairs,low utilization rate of light energy and high catalyst price.In summary,the above shortcomings were effectively solved through the three strategies of heterojunction construction,solid solution preparation and morphology control,and a photocatalyst with efficient and stable photocatalytic removal of indoor formaldehyde was prepared.At the same time,the physicochemical structure,optical properties,photochemical properties and photocatalytic properties of the catalyst were analyzed combined with a variety of characterization and analysis methods,and the mechanism of photocatalytic removal of indoor formaldehyde was proposed.The specific research content and results are as follows:1.Preparation and degradation of formaldehyde of 3D/2D Bi₂W_XMo_1-XO₆/g-C₃N₄The strategies of the construction of heterojunction and the preparation of solid solutions are implemented.3D/2D Bi₂W_XMo_1-XO₆/g-C₃N₄ catalysts were prepared by ion exchange method and used for photocatalytic removal of indoor formaldehyde.The successful synthesis of Bi₂W_XMo_1-XO₆ solid solution was proved by XRD,FT-IR,XPS and Rietveld refined analysis methods.It was found that when the preparation conditions were hydrothermal temperature 120℃,hydrothermal time 6 h and CN loading content of 30%,the prepared BWM6/CN had the best photocatalytic performance.The photocatalytic removal efficiency of indoor formaldehyde was 80.4%.Compared with only BWM6（38.7%）and CN（23.2%）,the photocatalytic efficiency is significantly enhanced,and the efficiency still reaches 74.1%after five cycles.Through the simulation of different indoor conditions（relative humidity,formaldehyde concentration）and photocatalytic formaldehyde removal test,the catalyst performed well in different scenes.The mechanism of BWM6/CN composite catalyst was studied by EPR,UPS and other characterization methods.It was found that BWM6 formed a Z-scheme heterojunction with CN,and hydroxyl radical and superoxide radical with strong oxidation ability were generated during the catalytic process.2.Preparation and degradation of formaldehyde of 2D/2D Bi₂W_XMo_1-XO₆/g-C₃N₄Based on the the strategies of the construction of heterojunction and the preparation of solid solutions,the strategy of the control of morphology is implemented.2D/2D Bi₂W_XMo_1-XO₆/g-C₃N₄catalysts were prepared by one-step hydrothermal method and applied for photocatalytic removal of indoor formaldehyde.The successful synthesis of Bi₂W_XMo_1-XO₆ solid solution was proved by XRD,FT-IR,XPS and Rietveld refined analysis methods.The optimum preparation conditions were determined as hydrothermal temperature 120℃,hydrothermal time 12 h and CN loading content of 20%.Compared with BWM6（43.1%）,CN（23.2%）and 3D/2D BWM6/CN（80.4%）,2D/2D BWM6/CN has better photocatalytic performance,and the efficiency of photocatalytic removal of indoor formaldehyde is 92.4%.The photocatalytic efficiency is significantly enhanced,and the efficiency still reaches 86.9%after five cycles.Through the simulation of different indoor conditions（relative humidity,formaldehyde concentration）and photocatalytic formaldehyde removal test,the catalyst performed well in different scenes.Compared with 3D Bi₂W_XMo_1-XO₆solid solutions,2D Bi₂W_XMo_1-XO₆ solid solutions extend the photo response range,promote interfacial charge transfer,reduce interfacial impedance,and expose more active sites with a larger specific surface area.The mechanism of BWM6/CN composite catalyst was studied by EPR,UPS and Density functional theory calculation.The Z-scheme heterojunction formed by BWM6 and CN significantly reduces the interface impedance between BWM6 and CN,and improves the separation efficiency of photogenerated carrier.Hydroxyl radical and superoxide radical with strong oxidizing ability played the main role in the photocatalytic removal of indoor formaldehyde.