Mesoporous WO₃/TiO₂ nanocomposites photocatalyst for rapid degradation of methylene blue in aqueous medium

This paper presents the wet chemical synthesis of WO₃/TiO₂ nanocomposites using hydrothermally prepared monoclinic WO3 and anatase TiO2 nanoparticles as composite matrices and filler, respectively. The nanocomposites were prepared in different compositions, i.e. WO₃:TiO₂ ratio (w/w) of (1:1), (1:3), and (3:1). Physicochemical properties of the resultant WO₃/TiO₂ nanocomposites were evaluated by Xray diffraction (XRD), scanning electron microscopy (SEM), BET N₂ adsorption-desorption isotherms, UV/vis, and Raman spectroscopy. The resultant nanocomposites exhibited a mesoporous structure with specific surface area of up to 11.5 m² g^-1, where TiO2 constituent contributed to higher surface area, especially in (1:3) ratio, and higher number of defect sites. While there was no impurities in the investigated nanocomposites as revealed by XRD analysis and Raman spectra, the WO₃:TiO₂ (1:3) nanocomposites showed the highest light harvesting ability indicated by higher absorption amplitude in both UV and visible regime. Three different kinetic models including pseudo-first-order, pseudo-second order, and Langmuir-Hinshelwood were applied to experimental data. The pseudo-second-order was found to be the best representing model and the adsorption kinetic studies indicated that chemisorption initially dominated the degradation mechanism. Finally, photocatalytic activity of nanocomposites was compared for photodegradation of methylene blue (MB) aqueous medium and in a good agreement with physicochemical properties, WO₃:TiO₂ (1:3) nanocomposites yielded the highest MB degradation rate (k ∼ 0.162 min^-1) and efficiency (96%) within 120 min under UV irradiation.