Abstract
Various W and Mo co-doped titanium dioxide (TiO2) materials were obtained through the EISA (Evaporation-Induced Self-Assembly) method and then tested as photocatalysts in the degradation of 4-chlorophenol. The synthesized materials were characterized by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy (RS), N2 physisorption, UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results showed that the W-Mo-TiO2 catalysts have a high surface area of about 191 m2/g, and the presence of an anatase crystalline phase. The co-doped materials exhibited smaller crystallite sizes than those with one dopant, since the crystallinity is inhibited by the presence of both species. In addition, tungsten and molybdenum dopants are distributed and are incorporated into the anatase structure of TiO2, due to changes in red parameters and lattice expansion. Under our experimental conditions, the co-doped TiO2 catalyst presented 46% more 4-chlorophenol degradation than Degussa P25. The incorporation of two dopant cations in titania improved its photocatalytic performance, which was attributed to a cooperative effect by decreasing the recombination of photogenerated charges, high radiation absorption capacity, high surface areas, and low crystallinity. When TiO2 is co-doped with the same amount of both cations (1 wt.%), the highest degradation and mineralization (97% and 74%, respectively) is achieved. Quinones were the main intermediates in the 4-chlorophenol oxidation by W-Mo-TiO2 and 1,2,4-benzenetriol was incompletely degraded.
Highlights
Among the advanced oxidation processes (AOPs), heterogeneous photocatalysis is considered as an efficient method for the degradation of organic pollutants in water and air [1,2]
A weight loss (9%) from room temperature to 200 ◦ C can be observed, which is assigned to desorption of water and residual organic solvents [22]
A significant weight loss (34%) between 200 ◦ C and 300 ◦ C is attributed to the elimination of P123 organic surfactant
Summary
Among the advanced oxidation processes (AOPs), heterogeneous photocatalysis is considered as an efficient method for the degradation of organic pollutants in water and air [1,2]. Numerous semiconductors have been investigated as photocatalysts. Titanium dioxide (TiO2 ) is the most promising and widely studied material for photocatalytic applications due to its chemical stability, high efficiency, photostability, high oxidizing power, abundance, nontoxicity, and low cost [3,4]. The main quality of TiO2 is attributed to oxidative power of hydroxyl radicals generated when the electrons are photoexcited by UV light absorption [5]. The recombination of the charge pair (holes and electrons) should not be ignored because it decreases the photoactivity.
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