A Visible Light-Driven Titanium Dioxide Photocatalyst Codoped with Lanthanum and Iodine: An Application in the Degradation of Oxalic Acid

Abstract

A series of photocatalysts was synthesized by codoping TiO 2 with lanthanum and iodine (La-I-TiO 2 ). The structure and properties of the catalysts were studied by X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) method, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra. The prepared anatase-phase La-I-TiO 2 (molar ratio 20:20:100) calcined at 400 °C had a BET surface area of 92.9 m 2 g -1 , and the crystallite size calculated from XRD data was ∼3.57 nm, and it had a remarkable absorption in the visible light range of 400-550 nm. The catalytic efficiency was tested by monitoring the photocatalytic degradation of oxalic acid under visible light irradiation. An optimum molar ratio of 20:100 La/TiO 2 was determined for the most efficient inhibition of the recombination of electron-hole pairs and the photocatalytic activity of La-I-TiO 2 calcined at 400 °C was significantly higher than that calcined at 500 or 600 °C in aqueous oxalic acid solution. The probable process of oxalic acid degradation was that it was first adsorbed onto the surface of the catalysts, where it reacted with valence band holes (h vb + ) and the surface-bound or adsorbed • OH radicals ( • OH ads ) as well as reactive oxygen species (ROS) derived from oxygen reduction by photogenerated electrons, and finally converted into CO 2 and H 2 O without any stable intermediate.

The photocatalytic and antibacterial activities of neodymium and iodine doped TiO2 nanoparticles

“…However when Nd was in excess, the space of charge region would become very narrow. The depth of penetration of light into TiO 2 would greatly exceed the space charge layer, and the recombination of the photoinduced electron-hole pairs became easier [22].…”

“…Particularly, according to Tojo et al [19], the photo-absorption in the visible region for I doped TiO 2 was much better than N doped TiO 2 . Recently, Zhao et al [ He et al [22] suggested that, by modification with a nonmetal and a metal oxide, the doped TiO 2 not only can be excited with visible light, but also its catalytic activity was enhanced.…”

Combinatorial doping of TiO2 with platinum (Pt), chromium (Cr), vanadium (V), and nickel (Ni) to achieve enhanced photocatalytic activity with visible light irradiation

“…25 Kato ) and TiO 2 codoped with Rh 3+ and Sb 5+ were also shown to improve photocatalytic activity for O 2 evolution under visible light irradiation. 27,28 However, there have been relatively few studies reported for double metal ion codoping of TiO 2 , while TiO 2 codoped with two nonmetallic elements (e.g., N and F codoping, 29,30 N and S codoping 31,32 ) or with metal ions and nonmetallic elements [33][34][35][36][37][38][39] (e.g., Cr and N codoping 35 Pt and N codoping, 36 V and N codoping, 37 …”

Synthesis and characterization of La2O3/TiO2−xFx and the visible light photocatalytic oxidation of 4-chlorophenol

“…Since nitrogendoped TiO 2 was first reported by Asahi et al [3], doping with non-metals such as N [3,[16][17][18][19], C [20], B [21][22][23][24], S [25], I [26] and F [27,28], has received a great deal of attention. Although these doped TiO 2 photocatalysts do have a response in the visible light region, there is no guarantee that they will enhance the photocatalytic activity [23].…”

“…Recently, lanthanum and iodine co-doped titania has been synthesized by He et al Their results showed that lanthanum can act as a barrier and thus facilitate charge carrier separation while the dopant lanthanum can create a Ti 3+ state, which retards the recombination of electron-hole pairs and extends the absorption into the visible light region. Moreover, the dopant iodine enters the lattice of TiO 2 and then I 5+ replaces Ti 4+ to maintain the charge balance [26]. Three positive roles for the fluorine dopant during photocatalysis are considered.…”