Z-scheme P-doped-g-C₃N₄/Fe₂P/red-P ternary composite enables efficient two-electron photocatalytic pure water splitting

Charge transfer in a semiconductor is crucial for photocatalytic pure water splitting. Herein, we construct a series of P-doped-g-C₃N₄/Fe₂P/red-P (PCN/Fe₂P/RP) ternary composite by in-situ phosphorization of a Fe₂O₃@C/g-C₃N₄ heterojunction. The as-prepared composite show substantially improved photocatalytic activity toward pure water splitting under visible light irradiation without adding any noble metal. The optimized composite containing 15 wt% Fe₂P presents the best activity, with the H₂ production rate of 429 µmol g⁻¹ h^−1, which is 107 and 39 times higher than that of pristine g-C₃N₄ and P doped g-C₃N₄ (PCN), respectively. This noble-metal-free photocatalyst presents a solar-to-hydrogen conversion efficiency of about 0.2% for pure water splitting. It is found that water splitting proceeds via a two-electron pathway with simultaneous production of H₂ and H₂O₂. The improvement relies on the formation of intermediate Fe₂P for rapid Z-scheme electron transfer from the midgap state of PCN to the valence band of RP. This work provides a versatile method for fabricating noble-metal-free photocatalyst with controlled charge transfer behavior for efficient photocatalytic pure water splitting.