Preparation And Photocatalytic Properties Of Tungsten Based Composite Photocatalysts

The valence orbital of tungsten is 5d⁴6s²,and the valence of tungsten often exists in the form of price+4 and+6.Most tungsten based materials are divided into co-catalyst and semiconductor,such as WS₂,WO₃ and Bi₂WO₆.Among these meterials,the+6 price of W atom occupies the center of the octahedron,and six apexes are dominated by O atoms,due to the unique physical and chemical properties of W based compounds.Meanwhile,W based materials rich in resources and low cost,which makes the WS₂ WO₃,and Bi₂WO₆ be widely utilized in photo-electrochromism,photocatalysis,solar cells,and other fields.Research contents of W based catalysts were listed as following:1.Construction of Z-scheme heterojunction has received widely attention in photocatalytic CO₂ reduction owing to its excellent redox capability and photoinduced electron-hole separation efficiency.Herein,a novel CuO nanoparticle/WO₃nanosheets 0D/2D Z-scheme heterojunction was synthesized by self-assembly method.The CuO nanoparticles decorated WO₃ nanosheet affords a close interface and short charge diffusion distance,which can effectively promote the separation efficiency of charge carriers.Moreover,the Z-scheme charge transfer mechanism simultaneously keeps the strong reduction capability of CuO and oxidation of WO₃,thus enhancing the photocatalytic CO₂ reduction performance.Resulting from the 0D/2D structural benefits and Z-scheme charge transfer mechanism,the CuO/WO₃ performs a much higher photocatalytic activity than pure CuO and WO₃by reducing CO₂ with H₂O vapor into CO under visible-light irradiation.This study constructs a novel Z-scheme heterostructure by combining different narrow-bandgap semiconductors,which can possess a rapid charge transfer rate and superior redox ability in CO₂ photoreduction.2.The highly efficient spatial carrier separation and abundant active sites are significant for CO₂ photocatalytic reduction efficiency.Herein,an ultrathin Bi₂O₃nanosheet/Bi₂WO₆ network heterostructure is successfully synthesized via a covalently bonded epitaxial growth strategy.Due to cosharing of the Bi-O tetrahedron between Bi₂O₃ and Bi₂WO₆,this heterostructure exhibits a compact interface,which can provide a rapid route for the charge transfer.Moreover,the pores generated from the hierarchical structure afford abundant exposed photocatalytic active sites.Thus,the optimal Bi₂O₃/Bi₂WO₆ heterostructure shows superior photocatalytic performance for CO₂ reduction with an ultrahigh selectivity as well as the removal of Rh B.Notably,the photocatalytic CO generation rate over Bi₂O₃/Bi₂WO₆ arrives at 17.39μmol·g^-1·h^-1,which is 18.0 and 4.2 times higher than bulk-Bi₂WO₆ and Bi₂WO₆ nanosheets,respectively,and the selectivity is of about 95.4%.Moreover,the Bi₂O₃/Bi₂WO₆ heterostructure also exhibits improved long-term stability,resulting from the firm heterointerface.Our studies present a conventient avenue to construct a high-efficiency heterostructure photocatalyst with a firm interface by the covalently bonded epitaxial growth method for CO₂ reduction.3.It is difficult to exploit excellent non-noble metal co-catalysts for economic fuel production.The 1T-WS₂ co-catalyst was synthsized by a facile solvothermal method.The 1T-WS₂/P25 composite was obtained by decorating the P25nanoparticles on the surface of 1T-WS₂ nanosheets.The CO and CH₄ generation rates of optimal 1T-WS₂/P25 arrive at 15.12 and 19.08μmol·g^-1·h^-1,which are 2.9 and 6.7times higher than that of single P25.The selectivity of CH₄ reaches to 80.6%,and the photocatalyst shows good cycling stability.The enhanced photocatalytic performance can be ascribed that 1T-WS₂ greatly accelerated the migration of photogenerated electrons and make the photogenerated electrons concentrate on the surface of the co-catalyst,which was conducive to the formation of CH₄.This work provides new insight into the surface engineering strategy modulate the reactivity and selectivity of CO₂ reduction product in photocatalysis.