Effect of W concentration in the organized Ti-W alloy oxide nanotubes array on the photoelectrocatalytic properties and its application in the removal of endocrine disruptors using real water matrix

Abstract

To evaluate the tungsten content on the photoelectrocatalytic properties of self-organized nanotubes grown by anodization on Ti-xW (wt%) alloys, where x is 0.5, 2.5 or 5.0, this work investigated the phase transformation of TiO2, the tungsten oxidation states in the oxide layers and their photoelectrocatalytic performance in the degradation of estrone (E1) and 17α-ethinylestradiol (EE2). These films were employed in photocatalytic and photoelectrocatalytic removals of hormones from synthetic and real water matrices. In synthetic water, E1 and EE2 removals, reached efficiencies of 92% and 71%, respectively, after 2 min under UV–Vis photoelectrocatalysis using NT/Ti-5.0W as catalyst. About 30 times longer was needed to degrade 77% of both hormones from the real water matrix due to the presence of other high organic charge. The high performance of the NT/Ti-5.0W was associated with the combination of doping (W-doped TiO2) and WO3 (W6+) heterojunction. However, this electrode had its stability compromised under long degradation times, mainly under visible light, due to a WO3 leaching process. As for NT/Ti-0.5W, the substitutional W-doped TiO2 contributed to its greater stability and efficiency for a long time. The low performance of NT/Ti-2.5W was justified by high density of oxygen vacancy and unfavorable position of its adsorption bands.