Theoretical Study on Binary Monolayer P₃S-I for Photocatalytic Overall Water Plitting

The utilization of visible light to split water into H₂ and O₂ offers a promising solution to address the escalating global energy crisis and environmental pollution. Compared to conventional three-dimensional (3D) photocatalysts, anisotropic two-dimensional (2D) materials exhibit enhanced photocatalytic activity due to their ultrahigh surface area, reduced charge migration distance, and improved efficiency. In this study, we employ a swarm-intelligence search combined with density functional theory (DFT) calculations to propose a novel series of stable 2D phosphorus sulfides, P_xS_y (x, y=1-6), as promising candidates for photocatalytic water splitting. The P₃S-I monolayer exhibits an optimal bandgap (2.485 eV), appropriate band edge positions (-3.52 eV for CBM and -6.00 eV for VBM at the HSE06 level), high carrier mobility (3246.85 cm² V^-1 s^-1 for μ_e along the y-direction and 1039.80 cm² V^-1 s^-1 for μ_h along the x-direction), and strong optical absorption coefficients (exceeding 1×10⁵ cm^-1 within the visible spectrum). Notably, the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are facilitated concurrently at the P and S sites, respectively, driven exclusively by photogenerated electrons and holes. The P₃S-I monolayer achieves a high photocatalytic water-splitting efficiency of 17.7 % in both acidic and neutral environments. These findings provide theoretical insights into the design of efficient 2D materials for visible-light-driven overall water splitting.