Sulfur Doped Lead Monoxide Superfine Powder Materials: Solid-State Synthesis, Characterization, Adsorption and Photocatalytic Property of Methylene Blue

Abstract

Sulfur doped lead monoxide (S–PbO) superfine powder materials with high visible light-driven activity were successfully prepared by a simple solid-state reaction method at low temperature using sodium dodecyl benzene sulfonate (SDBS) as a template. The samples were characterized by X-ray powder diffraction, high resolution transmission electron microscopy/energy-dispersive X-ray spectroscopy, UV–Vis absorption spectra, infrared spectroscopy, X-ray photoelectron spectroscopy and N2 adsorption–desorption. The effect of feed ratio on the microstructure of materials, the doping mechanism of sulfur and the adsorption mechanism of methylene blue (MB) on the material surface were discussed. In addition, the intrinsic relationships among the material structure parameters, the photocatalytic degradation of MB under visible light irradiation and the stability of materials were investigated. The results show that the S element is successfully incorporated into the (111) crystal plane of the orthorhombic β-PbO lattice as a S(IV) and S(VI) at the assistance of SDBS. The content of sulfur has a certain regulatory effect on the energy gap of the orthorhombic PbO, and there is a positive correlation among the photocatalytic property of MB, the content of sulfur, and the lattice spacing of (111) and (310) crystal plane. The adsorption of MB mainly depends on the interaction between the surface active sites (S–O bond) and hydroxyl groups, and the adsorption relaxation time under different sulfur content. Under visible-light irradiation at room temperature within 60 min, the photocatalytic degradation (wt%) rate of MB (C0 = 50 mg/L) follows an order of S–PbO(S:Pb = 0.05:0.95) (97.8%) > S–PbO(S:Pb = 0.10:0.90) (90.6%) > S–PbO(S:Pb = 0.15:0.85) (83.5%) > S–PbO(S:Pb = 0.20:0.80) (72.3%) > PbO (48.2%). The holes (h+) and hydroxyl radicals (·OH) are the main active species during the photodegradation of MB solution for the S-doped PbO materials. The S-doped PbO materials are of a p-type indirect semiconductor, and the loss of lead is very little in the MB solution, it is feasible to the S-doped PbO powder materials as photocatalysts.