Synergistic defect and doping engineering of novel green phosphorene for enhanced spatial carrier separation: A DFT-based strategy for high-efficiency overall water splitting

Green phosphorene (GP), a novel two-dimensional (2D) allotrope of phosphorus, has emerged as a promising photocatalyst for overall water splitting due to its layer-tunable band structure and exceptional charge carrier mobility. However, its practical application is severely limited by rapid electron-hole recombination, insufficient visible-light absorption, and catalytically inert surfaces. To address these challenges, we propose a synergistic defect and doping engineering strategy, systematically investigated through density functional theory (DFT) simulations. By introducing Stone-Wales (SW) defects and subsequent Bi doping (termed SW-1-GP@Bi), the modified GP exhibited remarkable photocatalytic enhancements, including an extended visible-light absorption with a redshifted spectrum, a near-optimal hydrogen evolution reaction (HER) Gibbs free energy ($\Delta G_H=0.05\mathrm{eV}$), and a significantly reduced oxygen evolution reaction (OER) overpotential of 0.51 V at pH = 9 under illumination. The enhanced performance originates from two key mechanisms: (1) SW defects spatially separate electron-hole pairs, suppressing recombination, and (2) Bi doping tailors the surface electronic structure, optimizing hydrogen and oxygen intermediates adsorption. Our work demonstrates that defect-dopant synergy can effectively activate inert basal planes of GP, achieving balanced HER/OER activities for standalone water splitting. This strategy provides a universal framework for designing high efficiency 2D photocatalysts toward scalable solar hydrogen production.