Wide Spectrum Active MoSe₂-based Composites For Efficient Photocatalysis

The environment pollution and the shortage of fossil fuel are two obstacles to human society.Semiconductor photocatalysis is a novel and environmental-friendly technology that uses the solar energy to destroy pollutants.Exploring wide spectrum active photocatalysts has become one of the core issues for photocatalysis.In this work,we report the design and fabrication of the MoSe₂ photocatalysts and their composites and examination of their photocatalytic activity.We solved two key problems faced in this field:one is the spectral response of MoSe₂ based composites,and the other is the reduction of the electron-hole pair recombination.The following summarizes the major achivement:（1）A fast microwave-assisted approach was developed to fabricate MoSe₂ samples via a reaction of the MoSe₂ precursor in an aqueous solution using a microwave system.The pH value was changed during the preparation process.Their photocatalytic activity in the degradation of MB was investigated under visible light irradiation.The photocatalytic activity of MoSe₂ is related to the pH value of the precursor solution.The MoSe₂ synthesized at pH value of 5 exhibits an optimal photocatalytic activity with a MB degradation rate of 90%.（2）The pure MoSe₂ was successfully synthesized via a simple solvothermal method.The pH value and reaction temperature were changed during the preparation process.Their photocatalytic activity in the degradation of MB and reduction of Cr（VI）was investigated under visible light irradiation.The photocatalytic activity of pure MoSe₂ is dependent on the pH value and reaction temperature.When the pH value is 7and the temperature is 180°C,the pure MoSe₂ achieves a highest MB degradation rate of 93%and Cr（VI）reduction rate of 71%.（3）MoSe₂-TiO₂ composites were obatained using the solvothermal method under the optimal preparation conditions（the pH value is 7 and the temperature is 180°C）.The weight ratios of Mo Se₂ to TiO₂ were changed during the preparation to get a series of composites.Their photocatalytic activity in the reduction of Cr（VI）was investigated under visible light irradiation.The photocatalytic activity of MoSe₂-TiO₂ composites is dependent on the proportion of TiO₂ in the composites.When the weight ratios of MoSe₂ to TiO₂ were 1:0.5,the composite achieves a highest Cr（VI）reduction rate of91%.（4）A novel hexagonal 2H-MoSe₂ photocatalyst with ultraviolet（UV）-visible-near infrared（NIR）light responsewas successfully synthesized via a simple solvothermal method.Their photocatalytic activity in the reduction of Cr（VI）was investigated under UV and visible even NIR light irradiation.The results indicate that MoSe₂ synthesized at pH value of 2 achieves the highest Cr（VI）reduction rates of 99%,91%and 100%under UV,visible and NIR lightirradiation,respectively.