g-C₃N₄/TiO₂-B{100} heterostructures used as promising photocatalysts for water splitting from a hybrid density functional study

Abstract

Fabrication of heterostructure has been shown to be a good strategy to improve photocatalytic performance. By using first-principles calculation based on hybrid density functionals, photocatalytic mechanism of g-C3N4/TiO2-B{100} heterostructures is...

Role of Interfacial Built-In Electric Field Induced by Fluorine Selective Substitution-Doped g-C3N4 in Photocatalysis of the g-C3N4/TiO2-B(001) Heterostructure: Type-II or Z-Scheme Photocatalytic Mechanism?

“…It is found that the geometry of F N2 @g-C 3 N 4 is a distorted open-ring structure due to the overwhelmingly strong Coulomb repulsion between the lone pair electrons on pyridine nitrogen atoms and the high electronegativity of the F atom. Compared with the band structures of pure g-C 3 N 4 in our previous study, 17 F doping promotes the overall band structures of g-C 3 N 4 to move toward the lower energy, indicating that the F-substitutiondoped g-C 3 N 4 is more stable. It is worth noting that F doping creates few impurity levels inside the band gap, which are attributed to C1 and C2 atoms nearby the dopant F atom, as one can see in Figure 1c,d.…”

“…The narrower band gap leads to the high utilization efficiency of visible light, and the suitable band alignment can effectively separate photoinduced electrons and holes. Our previous study 17 found that compared with the band gap of the TiO 2 -B bulk (3.22 eV), 18 the band From the projected weighted band structures and density of states for the F N2 @g-C 3 N 4 /TiO 2 -B(001) heterostructure as shown in Figure 4a,b, we can see that the band structures of F N2 @g-C 3 N 4 are weakly influenced by the substrate TiO 2 -B(001) surface. We note that the profile of the band structures of F N2 @g-C 3 N 4 in the heterostructure as well as its freestanding form are similar due to the weak interaction between layers in the F N2 @g-C 3 N 4 /TiO 2 -B(001) heterostructure, except for the energy shift and local perturbation, which one can see from Figures 1d and 4a.…”

“…They found the ability of photocatalytic CO 2 reduction of the TiO 2 / g-C 3 N 4 composite is more than 10 times that of pure TiO 2 and g-C 3 N 4 surfaces, implying that the TiO 2 /g-C 3 N 4 composite is an excellent noble-metal-free photocatalyst. Our recent study 17 shows that the g-C 3 N 4 /TiO 2 -B{100} heterostructures are potential photocatalysts for water splitting. Their band edges straddle the redox of overall water splitting, and the staggered band alignment promotes the spatial separation of the photoinduced electron−hole pairs.…”

“…Their band edges straddle the redox of overall water splitting, and the staggered band alignment promotes the spatial separation of the photoinduced electron–hole pairs. More importantly, the channel structure of TiO 2 -B and the huge hole in g-C 3 N 4 provide a pathway for the diffusion of protons to reach the surface of g-C 3 N 4 to complete the hydrogen evolution reaction (HER).…”

“…The difference between the work function (or Fermi level) of g-C 3 N 4 and TiO 2 is a powerful driving force, promoting the electron flow from g-C 3 N 4 to TiO 2 . Accumulation/depletion of space charge is generated at the g-C 3 N 4 /TiO 2 interface, resulting in a built-in electric field from g-C 3 N 4 toward TiO 2 . ,,, Our recent study reported that the built-in electric field as a driving force accelerated the directional migration and recombination of holes in the valence band maximum (VBM) of g-C 3 N 4 and electrons in the conduction band minimum (CBM) of TiO 2 , while the built-in electric field as an inhibiting force hindered the migration of electrons in the CBM of g-C 3 N 4 and holes in the VBM of TiO 2 . Then, the electrons and holes remained on g-C 3 N 4 and TiO 2 , respectively, to participate in the subsequent redox reaction.…”