SnS2/covalent organic framework S-scheme heterostructures for photocatalytic water splitting: insights from ground-state properties and nonadiabatic excited-state dynamics

Abstract

SnS₂/covalent organic framework (COF) van der Waals heterostructures (vdWHs) have emerged as excellent photocatalysts. This work investigates strain engineering of three SnS₂/COFs S-scheme vdWHs, whose electronic properties respond differently to applied strain due to varying effects of strain on interactions between different orbitals. The light absorption properties of SnS₂/COFs are sensitive to applied strain, enabling continuous tuning of the absorption wavelength and making them promising for optoelectronic applications. SnS₂/COF3 meets the requirements for photocatalytic water splitting in the pH range of 0–7 and shows the strongest visible light absorption among SnS₂/COFs, as well as the highest solar-to-hydrogen efficiency of 54.18% that surpasses that of most reported 2D vdWHs, making it a promising photocatalyst. As a key factor in determining photocatalyst performance, the excited-state carrier dynamics of SnS₂/COF3 are further investigated using time-domain nonadiabatic molecular dynamics simulations at 300 K. The carrier lifetime in SnS₂/COF3 depends on decoherence time and nonadiabatic coupling, both closely related to electron–phonon interactions. Compressive strain is found to suppress carrier relaxation and recombination, boosting the photocatalytic performance of SnS₂/COF3.