Enhanced optical absorption and photocatalytic water splitting of g-C3N4/TiO2 heterostructure through C&B codoping: A hybrid DFT study

Our theoretical research indicate that the electric field are generated in the direction of (C doped) TiO2 (101) surface to (B-doped) g-C3N4 monolayer for the pristine, C and B doped g-C3N4/TiO2, and higher band-edge potential on the (C doped) TiO2 (101) surface are observed compared to (B-doped) g-C3N4 monolayer. Thus, the pristine (2.591 eV), C-doped (2.663 eV) and B-doped (2.339 eV) g-C3N4/TiO2 are Z-scheme heterostructures, which promotes charge separation and retains a prominent redox ability. After C doping, the C 2p energy level is introduced which facilitate the separation of photoexcited carriers. The B-doped g-C3N4/TiO2 has a reduced bandgap and the mixing of B 2p and N 2p energy levels, promoting the red-shift of the optical absorption edge. The C&B codoped g-C3N4/TiO2 follows type-II charge transfer mode because of their synergistic effect in C and B atoms, which changes the direction of the built-in electric field. It also has a narrow bandgap (1.309 eV) and effectively separate electron-hole pairs leading to strong optical absorption ability in the range of 360 nme460 nm. The band-edges matching of the semiconductor photocatalyst and the direction of the built-in electric field jointly determine whether the charges are selected to be Z-scheme or II-type transfer mode. Based on g-C3N4/TiO2 for C or/and B (co)doping, their different charge transfer modes have been established and they are expected to show promising photocatalytic water splitting performance. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The research demonstrates that the C and B-doped g-C3N4/TiO2 exhibit higher band-edge potential in Z-scheme heterostructures, promoting charge separation and redox ability. The introduction of C 2p energy level after C-doping facilitates the separation of photoexcited carriers, while B-doping reduces the bandgap and promotes red-shift of the optical absorption edge. The C&B codoped g-C3N4/TiO2 follows type-II charge transfer mode, with a narrow bandgap and strong optical absorption ability.