Tuning the photoactivity of TiO₂ nanoarchitectures doped with cerium or neodymium and application to colour removal from wastewaters

Abstract

The impact of cerium (Ce) and neodymium (Nd) rare-earth metal doping of TiO2 prepared by hydrothermal method was investigated to tailor effective photocatalytic degradation of colored wastewater under UV or visible illumination. The hydrothermal treatment of TiO2 decreased the pHpzc from 6.3 to 3.1-3.8 favoring the affinity for cationic water contaminants. Doping with Ce and Nd modified the crystallinity and the morphology of the photocatalysts and significantly increased the BET surface area and the adsorption capacity of cationic dyes. The photocatalytic activity under UV light irradiation decreased due to shielding of the catalyst active area by excessive amount of dye adsorbed. Conversely, the photocatalytic activity of the Ce and Nd doped TiO2 increased under visible light irradiation by 1.2 times as a result of the dye photosensitization effect. It was demonstrated that two-steps dark adsorption and photocatalytic reaction or one-step simultaneous adsorption and reaction can produce significantly different results for the photocatalytic degradation of dyes in coloured waters, the rate being controlled by the competitive adsorption of the reacting organics and the H2O/OHspecies. The reaction is driven by the radical oxygen species (ROS) formed on the catalyst surface the nature of which, differs under UV or visible light irradiation. The Ce-doped TiO2 and Nd-doped TiO2 photocatalysts with 0.5% rare-earth content were found to be efficient in the degradation of MB in aqueous solution, removing the color and reducing the toxicity of wastewaters.

Design of porous Ni and rare earth metal (Ce, Ho, and Eu) Co-doped TiO2nanoarchitectures for energy conversion and storage applications

“…The TiO 2 nanoparticles were prepared using a hydrothermal method. 36,73,74 Briefly, 1 gram of TiO 2 P25 was stirred in 25 mL of 9 M NaOH solution for 1 hour. After 1 hour, the solution was heated in a Teflon autoclave in an oven at 120 °C for 24 hours, followed by centrifugation to remove excess solvent.…”

“…The widely used methods are surface modification, 27 doping with metals and non-metals, 24,28–30 creation of oxygen vacancies, 31 and development with other semiconductors. 32,33 Different metals that have been used to modify the optoelectronic properties of TiO 2 include nickel (Ni), 29,30 copper, 34,35 zinc, 34,35 iron (Fe), 36,37 silver (Ag), 34,38 and rare earth metals. 29,30,39–47 Due to its non-toxicity, abundance, and cost-effectiveness, Ni is the most-used dopant for TiO 2 .…”

Impact of Doping and Additive Applications on Photocatalyst Textural Properties in Removing Organic Pollutants: A Review

“…As shown in Table 2, metal and non-metal doping might control the surface area and pores of the particles. Vieira and co-workers [30] have reported that adding 0.5 wt.% Ce and 0.15 wt.% Nd enhanced the catalysts S BET by more than 100%. However, adding more than that is detrimental to the catalyst.…”

“…In several studies, the surface area and porous structure insignificantly affect the degradation of organic contaminants. For example, according to the findings by Vieira et al [30], the adsorption capacity of Ce-and Nd-TiO 2 photocatalysts were largely influenced by the zeta potential and charge density with a minor influence by the surface area. Meanwhile, Guo et al [42] reported that the degradation of Methylene Blue by S-doped BiVO 4 involved two synergistic factors, which were surface area and S-doping amount.…”

Physical and photocatalytic properties of Nd codoped (Ag, Cu)TiO2 thin films

“…On the other hand, doping with Nd modified the crystallinity and the morphology of the photocatalysts and significantly increased the BET surface area and consequently the adsorption capacity of cationic dyes. The photocatalytic activity under UV light irradiation decreased due to the shielding of the catalyst active area by an excessive amount of adsorbed dye [29]. H. Y.…”