Phase Engineering of 2D Violet/Black Phosphorus Heterostructure for Enhanced Photocatalytic Hydrogen Evolution

Rapid charge recombination has limited the application of black phosphorus (BP) as a visible light-responsive photocatalyst. Violet phosphorus (VP), another 2D phosphorus allotrope, has drawn extensive attention for its excellent semiconductor property. However, its photocatalytic activity for hydrogen (H₂) evolution is yet to be studied. Herein, a VP/BP heterostructure using a phase engineering strategy is constructed, wherein few-layered VP is interlaced with BP to create a well-matched heterophase interface by virtue of their identical chemical compositions and different crystal phases. Experimental and theoretical calculations reveal that VP and BP exhibit strong interaction at the heterophase interface, which is found effective in accelerating photogenerated electron transfer from BP to VP for improved charge separation efficiency. After being decorated with a Rh cocatalyst, the VP/BP heterostructure with utilization of visible light up to 700 nm shows ≈3- and 210-times greater photocatalytic H₂ evolution activity with respect to its counterparts. This study highlights feasibility of phase engineering and provides an alternative strategy in promoting charge separation as well as performance of photocatalyst.