Red Phosphorus/Carbon Nitride van der Waals Heterostructure for Photocatalytic Pure Water Splitting under Wide-Spectrum Light Irradiation

Developing active photocatalysts using wide-spectrum light is crucial to promote the application of photocatalytic water splitting. Elemental red phosphorus (RP) has attracted much attention as a potential nonmetal photocatalyst owing to its low cost, earth abundance, and narrow bandgap. Herein, RP nanosheets were synthesized and tightly combined with carbon nitride (CN) framework nanosheets to form RP/CN van der Waals (vdW) heterostructure. CN nanosheets could act as a substrate to generate RP nanosheets through a "confinement effect". This hybrid photocatalyst could utilize the incident light with the wavelength longer than 620 nm for pure water splitting, with hydrogen production activity of 367.0 μmol h-1g-1 under full arc illustration and 239.8 μmol h-1g-1 under visible light irradiation. The improved photocatalytic property was ascribed to the wide light absorption and intimate electronic coupling between 2D RP and 2D CN for accelerated charge transfer. Instead of O2, water was oxidized into H2O2 via a two-electron pathway, which could avoid the potential explosion by producing H2 and O2 simultaneously. This work proved the great potential of RP-based vdW heterostructures for solar-driven water splitting.