Photocatalytic overall water splitting Z-schemes for hydrogen production with the X@CTF-0/β-Sb (X = S, Se) heterostructures

Abstract

The covalent triazine framework (CTF-0) is believed to possess the potential to serve as a photocatalyst for overall water splitting, but its large bandgap constrains the solar-to-hydrogen (STH) efficiency. Here, we demonstrate that the STH efficiency can be boosted by constructing the CTF-0/β-Sb heterostructure and manipulating the band gap by the doped S or Se atoms in the CTF-0 monolayer. The electronic, optical, and thermodynamic properties are calculated to justify the photocatalytic Z-scheme for overall water splitting, and the interlayer transfers of the photogenerated carriers are investigated using non-adiabatic molecular dynamics simulations to understand the photocatalytic activity of the carriers. The electronic properties indicate that the band alignments hold a staggered character and there is a built-in electric field from the β-Sb to the CTF-0 monolayers in the heterostructures, which supports the photogenerated carriers to perform photocatalytic overall water splitting with Z-scheme and STH efficiencies of 13.28 % and 12.17 % can be achieved for the S@CTF-0/β-Sb and Se@CTF-0/β-Sb heterostructures. Moreover, the STH efficiencies remain increasing within 4 % biaxial strains, regardless of the tensile and compressive ones, implying that no need to worry about the effect of the smaller deformations on the photocatalytic performance in the preparation. Nonadiabatic molecular dynamics simulations show that the photocatalytic activities of the photogenerated carriers in the S@CTF-0/β-Sb are better protected in comparison with those in the Se@CTF-0/β-Sb heterostructures. However, the recombination times indicate that the latter can exert a better photocatalytic performance. Therefore, both the S@CTF-0/β-Sb and Se@CTF-0/β-Sb heterostructures are promising candidates for overall water-splitting for hydrogen production.