A new high efficiency visible-light photocatalyst made of SnS2 and conjugated derivative of polyvinyl alcohol and its application to Cr(VI) reduction

Abstract

This study focuses on the synthesis of a new high efficiency visible-light photocatalyst made of SnS2 and conjugated derivative (CPVA) from thermal dehydration of polyvinyl alcohol (PVA), and the evaluation of its performance in photocatalytic reduction of aqueous Cr(VI). SnS2/CPVA nanocomposites were synthesized via the procedures of (i) mixing of SnS2 nanocrystals and PVA in aqueous solution and evaporation of the aqueous solvent to generate SnS2/PVA nanocomposites, and (ii) thermal treatment of the SnS2/PVA nanocomposites for transforming their PVA into conjugated CPVA. The optimum conditions for synthesis of most efficient SnS2/CPVA nanocomposite were explored. The characterization by X-ray diffraction, Raman spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and elemental mapping indicated the formation of SnS2/CPVA nanocomposites. The photocatalytic experiments showed that SnS2/CPVA nanocomposite synthesized under the optimum conditions (SnS2/CPVA-1%-180°C-2h) had exceptionally higher photocatalytic activity than SnS2 nanocrystals, physical mixture of SnS2 nanocrystals and CPVA, SnS2/CPVC nanocomposite and TiO2/CPVA nanocomposite in the reduction of aqueous Cr(VI) under visible-light (wavelength>420nm) irradiation. The mechanism underlying the most enhanced photocatalytic activity of SnS2/CPVA-1%-180°C-2h was elucidated, based upon comparison between the optical, photoelectric and electrochemical impedance properties of SnS2 nanocrystals and different SnS2/CPVA nanocomposites. Furthermore, the effects of photocatalytic experiment parameters (including dosage of photocatalyst, and initial pH and concentration of Cr(VI) aqueous solution) on the Cr(VI) removal efficiency by SnS2/CPVA-1%-180°C-2h were also studied.