A Study For Photocatalytic Properties Of Transitional Metal Oxides MoO₂/WO₂ Heterostructure

Semiconductor photocatalytic technology plays a key role in alleviating the energy crisis and environmental pollution,especially the highly efficient semiconductor photocatalyst plays a very important role.However,most semiconductor photocatalysts do not match the bandgap and high probability of photo-carrier recombination,which greatly limits their practical application in the field of photocatalysis.Due to the characteristics of large surface area,abundant structure,and easy to control electronic structure,which provides a new opportunity for the design of novel two-dimensional semiconductor catalysts.In this paper,the photocatalytic properties of MoO2/WO2 heterojunction are discussed by first-principle method.The main conclusions are as follows:1.The electronic structure and photocatalytic properties of MoO2/WO2 interlayer heterojunctions are investigated by first principle method.Studies have shown that there are five stacking patterns in the MoO2/WO2 interlayer heterojunction.The binding energies of five stacking patterns are between 57.33-65.33 meV/atom,which are larger than the binding energies of double-layered graphene and graphene/boron nitride,indicating that MoO2/WO2 can form a stable van der Waals heterojunction.The bandgap of the MoO2/WO2 heterojunction is 1.71 eV,which is slightly smaller than the bandgap of the intact monolayer MoO2 and WO2(1.83 eV,1.88 eV).The band edge position of the MoO2/WO2 heterojunction indicates that it is a typical type ?heterojunction.From the picture of projected charge density,we can see that the valence band maximum(VBM)of the heterojunction is determined by the WO2 layer,while conduction band minimum(CBM)is contributed by the MoO2 layer,especially the local charge density of CBM and VBM demonstrate that the photogenerated electrons would be localized at WO2 layer and the photogenerated holes would be localized at MoO2 layer under the light irrigation.Thus,the effective separation of the photogenerated carriers is realized.In addition,the optical absorption spectra show that the absorption peak of MoO2/WO2 heterojunction is obviously higher than that of MoO2,WO2 in the range of visible light response.2.The crystal structure and electronic properties of A-MoO2/WO2 and Z-MoO2/WO2 heterojunctions are studied by first-principles calculation.The results show that the formation energies of the A-MoO2/WO2 and Z-MoO2/WO2 heterojunction tend to be constant with the width increasing.The electronic structure shows that the CBM and VBM of A-MoO2/WO2 heterojunction are both at ? point,which is a direct band gap semiconductor.While the VBM of Z-MoO2/WO2 heterojunction is located at? point,and the CBM lies between ? point and K point,which presents indirect band gap characteristics.The band gap decreases gradually with the width increasing and tends to be a constant.The projection charge density distribution indicates that the CBM is provided by MoO2 and the VBM is contributed by WO2,indicating that the in-plane MoO2/WO2 heterojunction can achieve the spatial separation of photogenerated electron-hole pairs and prolong the lifetime of photogenerated carriers.Our calculation results show that MoO2/WO2 heterojunction not only has a better optical response range than that of single MoO2 and WO2,but also can effectively achieve the spatial separation of photogenerated carriers and prolong the lifetime of photogenerated carriers.Especially for MoS2/WS2 heterojunction,the MoO2/WO2 heterojunction photocatalyst would not produce SO2 during the photocatalyst process,which reflects that MoO2/WO2 heterojunction is a kind of great potential photocatalytic material.