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

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. [Display omitted] •WO3 nanostructures were synthesized with three different acidic electrolytes.•The nanostructures that have shown the best photoelectrochemical behavior are those obtained with CH4O3S as electrolyte.•The degradation of diazinon has been carried out using photoelectrocatalysis.•After photoelectrocatalytic degradation of diazinon, 5 possible degradation compounds have been obtained.