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

Owing to the promising photocatalytic performance, the sheet-like WO was modified by depositing nanostructured CoO 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 CoO particles at the surface without altering the lattice of WO however, during the processing the cracking of disc was also evidenced. The FESEM and HRTEM analysis corroborated the uniform surface dispersion of CoO nanoparticles. The co-existence of 2+ and 3+ oxidation states of Co in the deposited CoO was examined by XPS analysis. The efficient trapping of excitons by CoO surface entities was witnessed in the emission measurements whereas the same was authenticated by the photo-electrochemical chronopotentiometry. The CoO loaded sheets exhibited substantially enhanced activity for the removal of 2,4,6-trichlorophenol as compared to pure WO 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 HO on the ease of removal process was also investigated.