Surface-grafted WO3/TiO2 photocatalysts: Enhanced visible-light activity towards indoor air purification

Regardless of the fact that tungsten trioxide (WO3) is recognized as one of the most promising photocatalysts for potential activity under visible light illumination, it still suffers from intrinsic drawbacks such as photocorrision and an unsuitable band gap structure for the reduction of molecular oxygen. To overcome these limitations we herein report for the first time in-situ synthesized WO3 nanoparticles which were coupled with commercial TiO2 (P25) via a simple impregnation method. The surface of the composites were additionally grafted with varying contents (0.005-0.3 wt%) of Fe(III) nanoclusters with their synergistic performance being investigated. The photocatalytic activities of the obtained materials were evaluated by monitoring the decomposition of the model compounds nitric oxide (NO) and acetaldehyde under UV and visible light illumination. A significant improvement of visible light sensitivity was attained in comparison with bare WO3/TiO2. Additionally the synthesized photocatalysts have been characterized by using x-ray powder diffraction(XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) spectroscopy, UV-vis diffuse reflectance spectroscopy and N-2 adsorption (BET) for specific surface area determination. The EPR results confirmed a direct charge transfer from the VB of the composites to the surface grafted Fe(III) nanoclusters, which are promoting multielectron reduction processes consequently resulting in the degradation of harmful gases.