Facile construction of 2D/2D BiOCl/NiAl-LDHs S-scheme heterojunctions for efficient photocatalytic dye and antibiotic degradation

2D/2D van der Waals heterojunctions have been proved to be a feasible strategy to enhance photocatalytic activity. In this work, two-dimensional (2D) BiOCl and layered double hydroxides (NiAl-LDHs) were composited using a simple mechanical mixing method at room temperature. The 2D/2D BiOCl/NiAl-LDHs S-scheme heterojunctions with a sheet-on-sheet interface contact were formed. The effects of interface contact and band structure between BiOCl and NiAl-LDHs on the photocatalytic properties were investigated. Experimental results showed that the reaction rate constants of BiOCl/NiAl-LDHs S-scheme heterojunctions for the degradation of methyl orange, methylene blue and levofoxacin were 13, 59 and 3 times of BiOCl and 141, 83 and 27 times of NiAl-LDHs, respectively. BiOCl/NiAl-LDHs heterojunctions displayed good stability and regeneration capacity. After four times of recycling, the degradation rates were more than 97 % for methyl orange and methylene blue, and 94.5 % for levofoxacin. The enhancement in photocatalytic activity was attributed to the formation of S-scheme van der Waals heterojunctions with sheet-on-sheet contact, which provided a short charge transfer distance and enabled rapid charge separation at the interface. The formation of S-scheme heterojunctions was confirmed by X-ray photoelectron spectroscopy, experimental calculations and radical trapping experiments. Using the same method, BiOX(X = Br and I)/NiAl-LDHs composites with sheet-on-sheet contact were also obtained. This work could provide valuable reference for constructing 2D/2D van der Waals heterojunctions.