Visible-Light-Driven Toluene Oxidation to Benzaldehyde over WO₃ Nanostructures

In this study, we have reported the impact of the surface morphologies and distinct exposed facets of WO3 nanoparticles on the photocatalytic oxidation of toluene. We successfully synthesized monoclinic-WO3 nanocubes (WNCs), hexagonal-WO3 nanosheets (WNSs), and nanorods (WNRs) with dominant exposed facets of (200), (110), and (110), respectively. The structural properties of the materials were thoroughly scrutinized using various analytical techniques, including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), UV-vis, and X-ray photoelectron spectroscopy (XPS). The formation energies of the oxygen vacancy surfaces of WO3(100) and WO3(110) planes and the binding energy of reactant molecules, including O-2 and toluene, were calculated using plane wave density functional theory (DFT). The WO3(100) surface is more active for the adsorption of O-2 (adsorption energy -8.8 eV) than the (110) surface (adsorption energy -4.4 eV) on the oxygen vacancy site. Toluene adsorption on the (100) surface is also found to be more favorable by 1.01 eV compared to that on the (110) surface. Overall, WNC(100) was more active for the oxidation of toluene to benzaldehyde than WNS(110) and WNR(110), which is in good agreement with the experimental results. WNCs demonstrated exceptional photocatalytic performance with a benzaldehyde formation rate of 650 mmol g(-1) h(-1). Additionally, it exhibited a high benzaldehyde selectivity (99%) and remarkable stability.