Enhanced photocatalytic activity of Ce3+–TiO2 for 2-mercaptobenzothiazole degradation in aqueous suspension for odour control

Abstract

Abstract:A series of cerium ion-doped titanium dioxide (Ce 3+ -TiO 2 ) catalysts with special 4f electron configuration was prepared by a sol-gel process and characterized by Brunauer-EmmettTeller method, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS), and also photoluminescence (PL) emission spectroscopy. The photocatalytic activity of Ce 3+ -TiO 2 catalysts was evaluated in the 2-mercaptobenzothiazole (MBT) degradation in aqueous suspension under UV or visible light illumination. The experimental results demonstrated that the overall photocatalytic activity of Ce 3+ -TiO 2 catalysts in MBT degradation was signigicantly enhanced due to higher adsorption capacity and better separation of electron-hole pairs.The experimental results verified that both the adsorption equilibrium constant (K a ) and the saturated adsorption amount ( max ) increased with the increase of cerium ion content. The results of XPS analysis showed that the Ti 3+ , Ce 3+ , and Ce 4+ ions reside in the Ce 3+ -TiO 2 catalysts. The results of DRS analysis indicated that the Ce 3+ -TiO 2 catalysts had significant optical absorption in the visible region between 400-500 nm because electrons could be excited from the valence band of TiO 2 or ground state of cerium oxides to Ce 4f level. In the meantime, the dependence of the electron-hole pair separation on cerium ion content was investigated by the PL analysis. It was found that the separation efficiency of electron-hole pairs increased with the increase of cerium ion content at first and then decreased when the cerium ion content exceeded its optimal value. It is proposed that the formation of two sub-energy levels (defect level and Ce 4f level) in Ce 3+ -TiO 2 might be a critical reason to eliminate the recombination of electron-hole pairs and to enhance the photocatalytic activity.

Characteristics and Photocatalytics Activities of Ce-Doped ZnO Nanoparticles

“…That might be the reason why the optimal dosage of ceria was 9 at% under UV illumination. Our results are consistent with the results of earlier studies of photoluminescence and photocatalytic in Ce-doped TiO 2 samples [39,41,42], which suggested that the lower photoluminescence might indicate fewer electron-hole recombination and lead to the increase in photocatalytic activity.…”

“…On the basis of our photocatalytic results, it is believed that the difference in photocatalytic activity with doping concentrations not really relates to the surface adsorption ability, but also relates to the influence of doping concentration on structure and the concentration of electron acceptor (Ce 4+ ions) and oxygen vacancies [36]. Li et al [39] based on photoluminescence measurements proved that Ce doping can accelerate the separation efficiency of charge carriers. According to their results the Ce 4f level plays an important role in interfacial charge transfer and elimination of electron-hole recombinations.…”

Nanoceria as antioxidant: Synthesis and biomedical applications

“…These defects, which are primarily surface oxygen vacancies, cause a change in the local electronic and valence arrangement that stabilizes the trivalent oxidation state (III). 11-13 Ceria and nanoceria can be found in several high-end research technologies, such as solid-oxide fuel cells,14 high-temperature oxidation protection materials,15 catalytic materials, 16,17 and more recently, solar cells. 18 Recently, ceria nanoparticles have emerged as a fascinating and lucrative material in biomedical science due to their unique ability to switch oxidation states between III and IV based on environmental conditions.…”

A Highly Efficient and Stable Visible-Light Plasmonic Photocatalyst Ag-AgCl/CeO<sub>2</sub>

“…Several studies have confirmed that Ce 4f plays vital role for CeO 2 in photocatalytic process [33] and they demonstrated that electrons can be more easily injected into 4f band of CeO 2 because the potential of 4f band of CeO 2 is a little more positive than that of the conduction band of TiO 2 . CeO 2 was chosen as the semiconductor in this work has other reason, that is, CeO 2 has excellent electrontransfer mediator ability under visible light [9], which is helpful to further enhance its charge separation ability.…”