Hybrid triazine-based g-C3N4(001)/anatase TiO2(001) heterojunction: Insights into enhanced photocatalytic mechanisms via DFT calculation

Understanding is far from satisfactory on the photocatalytic enhancement mechanism of g-C3N4/TiO2 composite by experimental methods. The objective of this study is to investigate the interface properties of the gC(3)N(4)(0 0 1)/ TiO2(0 0 1) (remarked as CN/T/(0 0 1)) heterojunction by the density functional theory calculations for exploring the enhanced photocatalytic mechanisms. The calculated band structures revealed that the CN/T/ (001) heterojunction was an indirect-gap semiconductor. The calculated energy gap (Eg) of the CN/T/(0 0 1) was much smaller than that of the TiO2(0 0 1) and g-C3N4(0 0 1) facet. Besides, the maximum value of valence band (VBM) and minimum value of conduction band (CBM) of CN/T/(0 0 1) was extended to a higher energy region than those of two side surfaces, suggesting the CN/T/(0 0 1) nanocomposite showed a longer redshift of absorption edge. A polarized field within the interface region was formed by the charge transfer between the TiO2(0 0 1) and g-C3N4(0 0 1) surface, which was beneficial to the separation of photo-generated carriers. These findings all indicated that the CN/T/(0 0 1) heterojunction demonstrated a type-II band alignment structure. The electronic structure analysis of TiO2(0 0 1), (101) and (100) facets indicated that the Fermi level of (001) and (101) facets occupied the position of conduction band. However, the Fermi level of (100) facets was still located at the top of the valence band. It is speculated that this is the reason why different crystal faces would construct different types of heterojunctions.

Automated summary

Through density functional theory calculations, it was found that the CN/T/(0 0 1) heterojunction has an indirect band gap, with a much smaller energy gap compared to the TiO2 and g-C3N4 facets, which is beneficial for the separation of photo-generated carriers.