Constructing a direct Z- scheme photocatalytic system based on 2D/ 2D WO3/ ZnIn2S4 nanocomposite for efficient hydrogen evolution under visible light

Constructing composite structures with intimate interfaces and favorable charge transfer routes is an effective way to obtain highly efficient photocatalysts. Herein, novel Z-scheme two-dimensional (2D)/2D WO3/ZnIn2S4 nanocomposites were successfully designed, fabricated and characterized. Driven by the strong electrostatic interactions between the positively-charged 2D WO3 nanosheets and the negatively-charged 2D ZnIn2S4 nanosheets, intimate contact interfaces were formed, which promoted the separation and transportation of electron-hole pairs in composites. The as-prepared WO3/ZnIn2S4 catalysts exhibited significantly enhanced photocatalytic H-2 evolution activities under visible light irradiation in comparison to the single ZnIn2S4 component. Moreover, cyclic tests revealed the high stability of the catalyst over four cycles of repeated use. These superior performances are ascribed to remarkably accelerated transfer and separation of charge carriers in the composites, which was verified by the results of photocurrent response, electrochemical impedance spectroscopy and photoluminescence. Electron spin resonance analyses proved the photocatalytic mechanism over 2D/2D WO3/ZnIn2S4 hybrids follows the special Z-scheme mode instead of the traditional double-transfer mode. This study is anticipated to offer fresh insight into the design and preparation of highly-efficient 2D ZnIn2S4-based Z-scheme catalysts for water splitting.