Comparative study of MoS2/MoO3, g-C3N4/MoO3 heterojunction films and their improved photocatalytic activity

We use the electrochemical deposition method to couple anodized MoO3 films with MoS2 and g-C3N4 (graphitic carbon nitride). The XRD, SEM, and XPS results show that MoS2/MoO3 and g-C3N4/MoO3 heterojunctions form. The coupling with MoS2 or g-C3N4 remarkably enhances the UV and visible light absorption and slightly increases the bandgap of the MoO3 film. Meanwhile, the loading amounts of MoS2 and g-C3N4 have little impact on their optical properties. The coupling with MoS2 or g-C3N4 facilitates the separation and transfer of the photogenerated charges in the MoO3 films. The photocatalytic activity of the MoO3 films is increased by 2.74 and 3.11 times by coupling with MoS2 and g-C3N4, respectively. The photocatalytic activity improvement should ascribe to the Z-scheme systems’ formation. In the Z-scheme systems, photogenerated holes in the valence bands of MoS2 and g-C3N4 would combine with photogenerated electrons in the conduction band of MoO3. The separation of photogenerated electrons in the conduction bands of MoS2 and g-C3N4 and photoexcited holes in the valence band of MoO3 is achieved spatially. The slight performance difference of MoS2/MoO3 and g-C3N4/MoO3 composite films should attribute to the oxidizing ability difference of the photogenerated electrons in the conduction bands of MoS2 and g-C3N4.