Two-dimensional Cs3Sb2I9/C2N van der Waals type-II heterostructure: a promising photocatalyst for high efficiency water splitting

Abstract

The development of high-efficiency photocatalysts for photocatalytic hydrolysis using solar energy and water resources is of great significance for alleviating the current energy shortage. Finding rational photocatalysts remains a major challenge and great efforts have already been made. Here we propose a novel two-dimensional perovskite-based vdW heterostructure (Cs₃Sb₂I₉/C₂N) and systematically investigate its stability, electronic and optical properties and the effects of applied biaxial strain based on the first-principles approach to investigate its ability as a photocatalyst for water splitting. In order to ensure the significance of the calculation results in guiding experiments, a hybrid functional was used for all the calculations on the electronic structure. The results show that the Cs₃Sb₂I₉/C₂N heterostructure has satisfactory dynamic and thermal stability, and exhibits the characteristics of type-II band alignment in the equilibrium configuration. Charge density difference, Bader charge analysis and work function further prove that the photogenerated electrons flow from Cs₃Sb₂I₉ to the C₂N monolayer by the influence of the interface dipole, which promotes the separation and transfer of photogenerated charge carriers and inhibits the recombination of the photogenerated charge carriers. Furthermore, the Cs₃Sb₂I₉/C₂N heterostructure has a suitable redox potential for photocatalytic water splitting and exhibits enhanced light absorption in the visible light region. In addition, the electronic and optical properties of the Cs₃Sb₂I₉/C₂N heterostructure can be tuned by strain, and the Cs₃Sb₂I₉/C₂N heterostructure always possesses photocatalytic ability after applying −2% to 6% biaxial strain. These results suggest that the Cs₃Sb₂I₉/C₂N heterostructure will be a promising candidate for water splitting photocatalysts.