Degradation of Diazinon based on photoelectrocatalytic technique using enhanced WO3 nanostructures: Mechanism and pathway

Abstract

In this work, a resistant and toxic pesticide called diazinon was degraded through the photoelectrocatalysis (PEC) technique using tungsten oxide (WO3) nanostructures, applying an external bias of 1VAg/AgCl and simulated solar illumination. For this, WO3 nanostructures have been synthesized using electrochemical anodization in 0.05 M hydrogen peroxide and 1.5 M of different acidic electrolytes: H2SO4, CH4O3S or HNO3. Morphology, composition and crystallinity of the samples were evaluated through Field Emission Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM) and Raman Spectroscopy. Then, the photoelectrochemical properties of the samples were analyzed by Photo-Electrochemical Impedance Spectroscopy (PEIS). The conclusion obtained with these studies was that the nanostructures obtained in the CH4O3S-H2O2 electrolyte presented better photoelectrochemical behavior than the others. The degradation process was checked by UV-Visible, and through Ultra High-Performanc liquid Chromatography and Mass Spectrometry (UHPLC-Q-TOF/MS) the courses of the experiments have been controlled and five possible degradation intermediates have been identified. Finally, after 24 h of experiment, 90% degradation efficiency has been achieved, since it has been possible to decrease from 20 ppm to 2 ppm.