In-situ construction of 2D/2D heterostructured ZnIn2S4/Bi2MoO6 Z-scheme system for boosting the photoreduction activity of Cr(VI)

The direct 2D/2D Z-scheme heterostructures of ZnIn2S4/Bi2MoO6 were rationally constructed by growing ZnIn2S4 ultrathin nanoflakes on the surface of Bi2MoO6 nanosheets, in situ, towards photocatalytic Cr(VI) reduction. After the tight contact of the ZnIn2S4 nanoflakes and the Bi2MoO6 nanosheets, internal built-in electric fields (IBEFs) with the direction from ZnIn2S4 to Bi2MoO6 are formed at the ZnIn2S4/Bi2MoO6 interface due to the electron (e−) transfer from ZnIn2S4 to Bi2MoO6 based on the XPS results. The IBEFs and the staggered alignment of band edges at the heterointerface favor the separation and migration of photoinduced carriers through the Z-scheme route, which is demonstrated according to the results of DMPO-ESR spin-trap experiments. The elegant Z-scheme system with a ZnIn2S4/Bi2MoO6 heterostructure effectively accelerates the spatial separation and migration of photoinduced e− and holes (h+), and then results in the stronger redox ability of charge carriers. Furthermore, the combination of ZnIn2S4 with Bi2MoO6 helps to extend the visible-light absorption range, so as to promote light harvesting, which also contributes to the enhanced photoreduction activity of Cr(VI). Therefore, the as-prepared ZnIn2S4/Bi2MoO6 heterostructures show obviously enhanced photocatalytic activity for Cr(VI) reduction as compared with pure Bi2MoO6 under visible light (λ ≥ 420 nm) irradiation. The optimized ZnIn2S4/Bi2MoO6 photocatalyst (ZIS/BMO-0.6) exhibits almost close to 100% of Cr(VI) reduction after 60 min of irradiation, which is higher than the majority of previously reported Bi2MoO6 and other semiconductor-based catalysts. Its reaction rate constant for photocatalytic reduction of Cr(VI) (0.0491 min−1) is more than one order of magnitude higher than that of pure Bi2MoO6 (0.00479 min−1). This work makes a contribution to constructing high-efficiency photocatalytic materials for environmental pollution remediation applications.