Interface Regulation And Photocatalytic Properties Of Two-dimensional WO₃-C₃N₄ Heterojunction

With recent economic growth and social advancement,the environmental issues brought on by the increased usage of fossil fuels have gained more attention.People constantly search for alternatives to traditional energy sources as a result of the concept of green chemistry.One of the most promising technologies is the sensible use of solar energy as a clean energy source for photocatalytic water-splitting hydrogen evolution and the production of organic compounds.In this study,we altered the photocatalyst and investigated the mechanism of reaction from the viewpoint of photocatalyst design.Through ultrasonic-assisted solvent molecular intercalation,we achieved the exfoliation of the lamellae of carbon nitride,which was prepared by the thermal polymerization of urea,successfully constructed graphitic carbon nitride structures with two atomic layer thicknesses and rich in nitrogen defect sites.Then,by adjusting the reagents during the solvent heat treatment,we prepared a variety of WO₃ catalysts with different structures,and the characteristics of carbon-coated tungsten oxide nanosheets were examined for the effects of NHPI sensitization.Finally,using the WO₃ nanosheets that had been synthesized,heterostructures were constructed to create MCNTWx heterojunction catalysts,and the correlation between heterostructure composition and photocatalyst activity was studied.The following are the primary contents:1.The design and function of carbon nitride defect sites.Hybrid alcohol molecule intercalation with ultrasonic assistance was used to successfully create a carbon nitride sheet layer CNN with two theoretical atomic layer thicknesses.The N-defect sites created during the exfoliation process had an impact on the subsequent in-situ reduction of Pt nanoparticles,and the CNN was used to tune the Pt nanoparticle size.The changes in surface groups and acidity caused by exfoliation were studied.The interaction of the surface N defects,hydroxyl groups,and Pt co-catalysts on the water molecule adsorption pattern affected the activity of the photocatalyst for water-splitting hydrogen evolution.2.Surface sensitization and structural modification of photocatalysts.Utilization of structure-directed regents,WO₃ nanoparticles,nanorods,and nanosheet structures were created with various selected crystallographic orientations.Amorphous carbon layers were used to coat the WO₃ surface to increase the hydroxyl distribution.The WO₃-NHPI photocatalysts were prepared by NHPI sensitization,using photocatalytic benzylamine coupling as a model reaction.The key determinants of the higher activity were the expansion photoresponse range of NHPI and the reduced carrier complexation efficiency in multiphase photocatalysts.3.The design of composite heterojunction structures.An in-situ composite method was used to thermally polymerize WO₃ nanosheets with melamine to create WO₃-C₃N₄heterojunction photocatalysts.The two-dimensional lamella of MCN achieves a uniform spatial dispersion of WO₃nanosheets,resulting in a higher specific surface area of the MCNTWx photocatalysts.The considerable increase in the activity of photocatalytic hydrogen production resulted from the tight interface between the two catalysts,which confers heterojunction photocatalyst narrower forbidden band width and higher carrier use efficiency.The addition of WO₃ reduces the impedance and causes the synthesis of fresh W-N chemical bonds,both of which alter the original energy band shape,resulting in the WO₃-C₃N₄ heterojunction photocatalysts with higher photogenerated current intensity and electron density.