Synthesis, growth mechanism and photocatalytic property of CdS with different kinds of surfactants

Abstract

CdS is a well-known visible-light-sensitive semiconductor and has been widely used in photocatalysis. In order to improve the photocatalytic activity of CdS, controllable synthesis with different morphologies has been focused on. In this work, CdS structures with different kinds of surfactants were synthesized by the hydrothermal method. The as-prepared samples were characterized by powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), ultraviolet-visible spectroscopy (UV-Vis), and fluorescence spectroscopy (PL). Their photocatalytic activities were evaluated by the photocatalytic degradation of methylene blue (MB) under simulated visible-light irradiation. The XRD and EDS results revealed that fishbone-like CdS exhibited the hexagonal phase. The FESEM results showed that the morphologies of CdS indicated microsphere structures, flower-like structures, and branch-like structures when we added hexadecyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyethylene glycol (PEG 2000), respectively, as surfactants. The possible growth mechanism of CdS with different surfactants was explained. The UV-Vis results showed that the band gap of fishbone-like CdS was 2.32 eV, while the band gaps of CdS were 2.22 eV, 2.30 eV, and 2.31 eV for CTAB, SDS, and PEG 2000, respectively, when the concentration was 0.005 g mL⁻¹. The photocatalytic results showed that the highest degradation rates of MB were 90.0%, 87.9%, and 87.5% for the different kinds of surfactants, which were consistent with the UV-Vis and PL results. The CdS microspheres displayed photocatalytic stability to MB. The trapping experiments indicated that the photogenerated electrons played a key role in the photocatalytic degradation of MB. Briefly, different kinds of surfactants have obvious effects on the structure and photocatalytic performance of CdS.