Construction of metal-free dual S-scheme heterojunction photocatalysts by rational band alignment for efficient hydrogen evolution

Designing ternary heterojunction photocatalysts is regarded as a compelling approach to attain exceptional photocatalytic activity. However, they always suffer from poor interfacial contact and unclear charge transfer pathways. Herein, a metal-free dual S-scheme heterojunction photocatalyst comprised of black phosphorus (BP), carbon nitride (CN), violet phosphorus (VP) was designed by electrostatic self-assembly. The non-metallic feature of the BPCNVP heterostructure facilitates to form strong interfacial contact by coordinating active P sites in VP and BP with N atoms in CN. Notably, a definite dual S-scheme heterojunction configuration is achieved by rational band alignment of VP and BP, respectively, which significantly boosts the driving force for charge separation. The BPCNVP heterostructure exhibited a hydrogen evolution rate of 1669μmol h^-1g⁻¹ with excellent stability, surpassing most reported metal-free photocatalysts. This work demonstrates that the design of dual S-scheme heterojunction by metal-free materials provides valuable insights into the intricate reaction mechanism of ternary heterojunction photocatalysts.