Fabrication of highly active Melem/Zn0.25Cd0.75S composites for the degradation of bisphenol A and methyl orange under visible light irradiation

Metal-free polymeric catalyst hold great promise owing to their abundant sources, low-cost fabrication and easy processibility. Melem, an important intermediate during condensation of melamine rings to graphitic carbon nitride (g-C3N4), was synthesized by simple solid phase polymerization process. A novel Melem/Zn0.25Cd0.75S composite was fabricated through a facile one-step hydrothermal method. The as-products were characterized by X-ray diffraction (XRD), UV-vis DRS spectroscopy, fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM). The TEM and HRTEM results reveal that Zn0.25Cd0.75S nanoparticles and Melem closely contact with each other to form an intimate interface. The as-prepared composites exhibit significantly enhanced visible light photocatalytic performance for the degradation of Methyl orange (MO) and Bisphenol A (BPA), which could be attributed to the effective photo-induced charges transfer and separation in Melem/Zn0.25Cd0.75S composites. On the basis of radical scavenger experiments, superoxide radicals and holes are suggested to play a critical role in MO degradation over Melem/Zn0.25Cd0.75S heterojunctions. A possible mechanism for charge separation and transfer in the Melem/Zn0.25Cd0.75S composites was proposed to explain the enhanced photocatalytic performance.