ZnCo2S4/Bi2WO6 S-scheme heterojunction for efficient photocatalytic hydrogen evolution: Process and mechanism

The S-scheme heterojunction ZnCo2S4/Bi2WO6 is constructed by decorating ZnCo2S4 nanoparticles on Bi2WO6 nanosheets and applied to produce hydrogen photocatalytically. In simulated visible light conditions, the photocatalytic hydrogen evolution of 15-ZnCo2S4/Bi2WO6 is significantly enhanced (18.16 mmol g−1 h−1), surpassing the performance of original ZnCo2S4 and Bi2WO6. When measured at 420 nm, the apparent quantum efficiency (AQY) is 13.2%. A staggered band structure, an internal electric field (IEF), the band bending, and an S-scheme charge-transfer route are confirmed by calculations and characterization. As a result of the unique and fast charge transfer path, the useless electrons in conduction band (CB) of Bi2WO6 and holes in valence band (VB) of ZnCo2S4 could be recombined rapidly. Consequently, photogenerated holes in VB of Bi2WO6 and electrons in CB of ZnCo2S4 are separated efficiently. The work provides a method for the development of highly effective and cost-effective S-scheme heterojunctions for the production of hydrogen by photocatalysis.