Activation of persulfate ions by TiO₂/carbon dots nanocomposite under visible light for photocatalytic degradations of organic contaminants

In this study, we synthesized TiO₂/carbon dots (TiO₂/C-Dots) powders and their photocatalytic performances were exceptionally improved under visible light in removals of different organic pollutants using persulfate anions. The characteristic of as-synthesized photocatalysts were studied by X-ray diffraction, high resolution transmission electron microscopy, scanning electron microscopy, energy dispersive analysis of X-rays, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, Fourier transform-infrared, photoluminescence spectroscopy, and Brunauer–Emmett–Teller surface analysis. Among the synthesized samples, the TiO₂/C-Dots (0.50 mL) nanocomposite had the greatest photoactivity. In addition, the removal rate constant of RhB by this photocatalyst in the existence of 1.48 mM persulfate ions was 439 × 10⁻⁴ min⁻¹, which is almost 33.3, 3.35, 2.60, and 2.41-folds premier than those of the pure TiO₂, persulfate, TiO₂/persulfate, and TiO₂/C-Dots (0.50 mL) samples, respectively. Reactive species scavenging experiments revealed that ^·SO₄⁻ was generated following the addition of persulfate ions, whereas ^·O₂⁻ and h⁺ were predominantly responsible for the degradation of pollutants. At last step, the band alignments were obtained by electrochemical studies and the mechanism for boosted photocatalytic ability in the presence of persulfate anions was suggested. The photocatalyst could be regenerated for five repeated use.