An Understanding of the Photocatalytic Properties and Pollutant Degradation Mechanism of SrTiO₃ Nanoparticles

Abstract

Strontium titanate nanoparticles have attracted much attention due to their physical and chemical properties, especially as photocatalysts under ultraviolet irradiation. In this paper, we analyze the effect of heating rate during the crystallization process of SrTiO3 nanoparticles in the degradation of organic pollutants. The relationship between structural, morphological and photocatalytic properties of the SrTiO3 nanoparticles was investigated using different techniques. Transmission electron microscopy and N2 adsorption results show that particle size and surface properties are tuned by the heating rate of the SrTiO3 crystallization process. The SrTiO3 nanoparticles showed good photoactivity for the degradation of methylene blue, rhodamine B and methyl orange dyes, driven by a nonselective process. The SrTiO3 sample with the largest particle size exhibited higher photoactivity per unit area, independent of the molecule to be degraded. The results pointed out that the photodegradation of methylene blue dye catalyzed by SrTiO3 is caused by the action of valence band holes (direct pathway), and the indirect mechanism has a negligible effect, i.e. degradation by O2 (-•) and (•) OH radicals attack.

The Role of Nb Addition in TiO2 Nanoparticles: Phase Transition and Photocatalytic Properties

“…To evaluate the effect of Nb adding to the photocatalytic properties of TiO 2 , photocatalytic experiments were performed using the samples annealed at 400 and 900 °C. The photocatalytic activity was probed quantifying the removal of methylene blue (MB) and rhodamine B (RhB) dyes, following the procedure previously reported by our research group, where the samples were immersed in 20 mL of an aqueous solution of dye (20 mg L −1 ) and kept under UV illumination. The beakers were placed in a photo‐reactor at controlled temperature (25 °C) with six lamps (Philips UV‐light lamps, 15 W).…”

“…Among the main environmental problems, highlighted the pollution of air, soil, and water, which are essential sources for human beings. With respect to decontamination, the treatment of waste water and pollutant degradation using photocatalysts has been considered one of the most promising and eco‐friendly approach …”

The role of counter-ions in crystal morphology, surface structure and photocatalytic activity of ZnO crystals grown onto a substrate

“…The net charge (neutral, cationic and anionic) of an organic pollutant and the surface charge of a photocatalyst can influence the photooxidation process, since the interactions between the organic molecule and the photocatalyst are possibly completely different. While the MB dye forms cationic species as it is solubilized in water, the RhB dye is found to be a zwitterionic molecule in the 7-9 pH range; therefore, the net charge in the solution is expected to be zero [78,79].…”

“…About the mechanism responsible for organic pollutant oxidation, it can occurs by two main mechanism, direct and indirect oxidation [80][81][82][83][84]. In the direct oxidation when an electron-hole pair is formed by irradiation, the hole will migrate to the material surface, oxidizing the adsorbed compound on the semiconductor surface, while in the indirect oxidation, the electron-hole pair acts to form free radicals ( • OH, O 2 -• ) from surface groups [79,85]. Therefore, the direct oxidation tends to be a selective process, since occurs by adsorption of compounds in semiconductor surface.…”

Enhancement in Photocatalytic Activity of SrTiO3 by Tailoring Particle Size and Defects

“…The emerging pollutants in an aquatic environment have become a world‐wide issue of research in the last few decades . Photocatalysis is an ultimate solution for solving the environmental issues by degrading the nonbiodegradable and toxic contaminants or pollutants present in the wastewater through a very economic, eco‐friendly and nontoxic procedure .…”