Z-scheme AgBr@Ag/CoAl layered double hydroxide heterojunction for superior photocatalytic Cr(VI) reduction under visible light

Construction of the Z-scheme heterojunction photocatalytic system is a promising strategy for improving the catalytic activity of photocatalysts. Herein, a novel Z-scheme AgBr@Ag/CoAl layered double hydroxide (LDH) photocatalyst was successfully prepared. The AgBr@Ag/LDH composites displayed superior performance for Cr(VI) reduction under visible light. The optimal composite with a 10 wt% silver content showed the highest photocatalytic activity, which was 12.2 and 12.8 times greater than that of LDH and AgBr, respectively. Furthermore, this composite also exhibited good photocatalytic stability towards Cr(VI) reduction without an obvious decrease after 5 cycles. The formation of a Z-scheme heterojunction in the AgBr@Ag/LDH composite effectively promoted the separation of photogenerated electron-hole pairs and kept the electrons with a high reducing capability in the conduction band of LDH, thus leading to its excellent photocatalytic activity towards the reduction of Cr(VI). This study may provide an insight into the design of the LDH-based Z-scheme photocatalytic systems for Cr(VI)-containing wastewater treatment. [Display omitted] •A visible-light responsive Cr(VI) reduction photocatalyst was synthesized and characterized.•The composite exhibited excellent photocatalytic activity towards Cr(VI) reduction.•The interfacial charge transfer in AgBr@Ag/LDH was along Z-scheme pathway.•A possible photocatalytic mechanism for Cr(VI) reduction was proposed.