Polyoxometalate-based yolk@shell dual Z-scheme superstructure tandem heterojunction nanoreactors: encapsulation and confinement effects

Abstract

Flower-ball-like ZnIn₂S₄@hollow dodecahedral polyoxometalate (K₃PW₁₂O₄₀)@flower-shell-like ZnIn₂S₄/Ag₂S yolk@shell dual Z-scheme superstructure tandem heterojunction nanoreactors are fabricated through a two-step hydrothermal method combined with a cation exchange strategy. Hollow dodecahedral K₃PW₁₂O₄₀ acts as a bridge to form the special yolk@shell dual Z-scheme superstructure tandem heterojunction between two types of ZnIn₂S₄. Due to the encapsulation and confinement effects of the nanoreactors, the size of flower-ball-like ZnIn₂S₄ in hollow dodecahedral K₃PW₁₂O₄₀ is limited to form a yolk@shell structure, which favors light multi-reflection. The surface plasmon resonance (SPR) effect of Ag₂S nanoparticles extends the photoresponse to visible light and near-infrared regions. The resultant tandem heterojunction nanoreactors exhibit excellent photocatalytic degradation of tetracycline hydrochloride (∼99%) and hydrogen evolution (2107.3 μmol h⁻¹ g⁻¹) performance, which are several times higher than those of the pristine one. This is ascribed to the formation of a dual Z-scheme tandem heterojunction favoring spatial charge separation, the SPR of Ag₂S and yolk@shell hollow structure benefiting light utilization and mass transfer, and the encapsulation and confinement effects of the special nanoreactors facilitating the complete catalytic reaction and stability. This work provides an efficient strategy for constructing highly efficient tandem heterojunction photocatalysts.