The efficacy of Co3O4 loaded WO3 sheets for the enhanced photocatalytic removal of 2,4,6-trichlorophenol in natural sunlight exposure

Abstract

Owing to the promising photocatalytic performance, the sheet-like WO3 was modified by depositing nanostructured Co3O4 at the surface. The appearance of the varying dual absorption edges in the optical analysis exposed the composite nature of the synthesized materials. The structural analysis revealed the deposition of Co3O4 particles at the surface without altering the lattice of WO3 however, during the processing the cracking of disc was also evidenced. The FESEM and HRTEM analysis corroborated the uniform surface dispersion of Co3O4 nanoparticles. The co-existence of 2+ and 3+ oxidation states of Co in the deposited Co3O4 was examined by XPS analysis. The efficient trapping of excitons by Co3O4 surface entities was witnessed in the emission measurements whereas the same was authenticated by the photo-electrochemical chronopotentiometry. The Co3O4 loaded sheets exhibited substantially enhanced activity for the removal of 2,4,6-trichlorophenol as compared to pure WO3 in the complete spectrum and visible region of natural sunlight exposure. The progress of the degradation process was monitored by HPLC whereas the degradation products were identified by GC–MS. The measurement and identification of the ion released during the photocatalytic process facilitated the estimation of the probable route and role of reactive oxygen species involved in the removal process. Although, the careful analysis of the findings from the analytical tools revealed the major involvement of hydroxyl radicals however, the role of superoxide anions was also exposed. An alternative mechanism of the generation of the superoxide radical involving the 2+ and 3+ oxidation states of Co was also proposed. The effect of the pH and the added concentration of H2O2 on the ease of removal process was also investigated.