S-doped ZnO photoelectrode modified with silver and platinum nanoparticles and their photocatalytic activity for progesterone degradation

Abstract

Zinc oxide doped with sulfur (ZnO-S) has presented improved photocatalytic activity under visible irradiation. In this work, ZnO-S film was efficiently prepared by thermal decomposition from zinc sulfide (ZnS) in an oxidizing atmosphere. X-ray diffraction analysis (XRD) showed ZnS phase transformation occurred from cubic sphalerite to ZnO hexagonal wurtzite at temperatures between 500 and 600 °C. ZnO-S electrodes prepared onto a transparent conductive substrate were modified by silver (Ag0) or platinum (Pt0) nanoparticles (NPs). X-ray photoelectron spectroscopy (XPS) confirmed that sulfur was incorporated into ZnO structure. Field Emission Gun-Scanning Electron Microscope (FEG-SEM) images showed that occur a drastic modification in the particle morphology of the films treated at distinct temperatures. Photoelectrochemical investigation displayed a negative photopotential (∆E<0) for all photoelectrode investigated as well as superior photocurrents for samples modified with metallic Ag0 and Pt0 NPs. In order to investigate the photoelectroactivity, ZnO-S6, Ag0/ZnO-S6, Pt0/ZnO-S6 and commercial ZnO electrodes were used to degrade progesterone solution under polychromatic irradiation. The superior performances were observed for ZnO-S films functionalized with Ag0 or Pt0. Therefore, the results showed advances in the degradation of organic contaminants in the water treatment process and possible contributions to a better use of solar radiation.