Overcoming Defect Limitations in Photocatalysis: Boron‐Incorporation Engineered Crystalline Red Phosphorus for Enhanced Hydrogen Production

Abstract Photocatalytic hydrogen evolution (PHE) from water splitting is a promising technology for clean and renewable energy production. Elemental crystalline red phosphorus (CRP) is purposefully designed and developed for PHE reaction. However, the photocatalytic activity of CRP is limited by its intrinsic P vacancy (V_P) defects, which lead to detrimental charge trapping at deep states and hence its severe recombination. To address this issue, a boron (B) incorporated CRP (B‐CRP) photocatalyst is tailored, synthesized via a simple and mild boric acid‐assisted hydrothermal strategy. The incorporation of B effectively fills the V_P defects, reducing deep trap states (DTS) and introducing beneficial shallow trap states (STS) within the band structure of CRP. This defect engineering approach leads to enhanced photocatalytic activity, with B‐CRP achieving a PHE rate of 1392 µmol g⁻¹ h⁻¹, significantly outperforming most reported elemental photocatalysts in the literature. Density functional theory (DFT) simulations and ultrafast spectroscopy support the constructive role of B‐dopant‐induced STS in prolonging active charge carrier lifetimes, promoting more efficient photocatalytic reactions. The findings not only demonstrate the effectiveness of B‐CRP as a photocatalyst but also highlight the usefulness of dopant‐induced STS in advancing PHE technologies.