Preparation and photocatalytic activity of composite metal oxides derived from Salen-Cu(II) intercalated layered double hydroxides

Copper(II) Schiff-base Complexes (Salen-Cu(II)) intercalated zinc-chromium layered double hydroxides (ZnSBCuCr-LDHs) were successfully prepared via coprecipitation. Then, a novel photocatalytic material Zn-Cu-Cr composite oxides (ZnSBCuCr-MO) was prepared after calcination at 500 °C with ZnSBCuCr-LDHs as precursor. The structure and properties of the materials were thoroughly characterized by powder X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES), ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the materials were investigated by photodegradation of a cationic dye Rhodamin B (RhB), which was hard to adsorb by LDHs. The effects of the photocatalyst dosage, the initial pH and temperature of RhB solution on the photocatalytic efficiency were discussed. The results showed that ZnSBCuCr-MO displayed higher photocatalytic activity for RhB than calcined ZnCr-LDHs (ZnCr-MO) and calcined ZnCuCr-LDHs (ZnCuCr-MO). Meanwhile, ZnSBCuCr-MO exhibited better stability and reusability. In addition, the possible photocatalytic mechanism and degradation pathway for RhB were studied through density functional theory (DFT) calculation of the RhB molecule, UV-vis absorption variation and LC-MS analyses of the RhB solution.