Novel X@g-C3N4/GaP3 (X = S, Se) heterostructures for photocatalytic overall water splitting with Z-scheme

S or Se atoms are doped into the g-C₃N₄/GaP₃ heterostructure to promote the solar-to-hydrogen (STH) efficiency. The fully optimized geometrical structures demonstrate the doped S and Se atoms are possibly located at either out-plane or in-plane sites on the g-C₃N₄ monolayer of the heterostructure. The electronic properties reveal that the photocatalytic Z-schemes with a maximum STH efficiency of 27.53 % or 24.77 % can be achieved for the out-plane S or Se-doped g-C₃N₄/GaP₃ heterostructure, respectively. The migration and recombination of the photogenerated carriers are explored using non-adiabatic molecular dynamics simulation. The outputs demonstrate that the electron/hole lifetimes in photocatalytic hydrogen/oxygen evolution reactions are similar, indicating that the activities of the photogenerated carriers are effectively protected. However, the electron-hole recombination of the Se@g-C₃N₄/GaP₃ heterostructure is faster, implying that the photocatalytic Z-scheme is more efficient. Gibbs free energies show that the Se@g-C₃N₄/GaP₃ heterostructure can drive the hydrogen evolution reactions to proceed spontaneously. These facts indicate that the S@g-C₃N₄/GaP₃ and Se@g-C₃N₄/GaP₃ heterostructures are competitive candidates for overall water splitting with photocatalytic Z-schemes for hydrogen production.