De-Colorization Activity Enhancement of Degussa P25 TiO₂via the Formation of p-n Heterojunction by Carboxylic Modification

Abstract

The visible-light-driven photocatalytic activity of Degussa P25 TiO 2 is effectively promoted by modifiers containing carboxylic groups through impregnating cyclohexanol and a low-temperature heating treatment. The superficial TiO 2 modified with the organic modifiers creates certain low band-gap states to enhance its visible-light activity. The carboxylic-modified TiO 2 dispersed on the P25 surface shows the p-type semiconductor characteristics, confirmed by the photocurrent responses under the open-circuit state and blue-light irradiation. Accordingly, a p-n heterojunction between the superficial modified TiO 2 and underneath P25 enhances the separation of photo-excited electron/hole pairs, resulting in the higher photocatalytic activity. During the photo-electrocatalytic de-colorization test, the photo-excited electrons are further withdrawn by the positive potential bias toward the graphite cathode through the electric circuit, which favors the oxygen reduction reaction (ORR) of two-electron transfer to effectively generates H 2 O 2 for organic pollutants decomposition. Therefore, methylene blue (MB) can be efficiently de-colorized on the carboxylic-modified P25 under the visible-light irradiation meanwhile the de-colorization rate is enhanced under the photo-electrocatalytic mode.

Solar light efficient photocatalytic activity degradation of emergent contaminants by coated TiO2 nanoparticles

“…The results shown in Figure S5 exhibit similar excitonic PL emission bands for the coated and uncoated NP samples, indicating that the oligomers adsorbed on TiO2 NP did not generate any new emission peaks on the PL spectra. 17 Besides, the PL emission intensity did not decrease upon NP coating with oligomers, meaning that the charge separation efficiency of the photo-excited e-/h+ pairs was not affected by the surface modifier and the e-/h+ recombination process was not altered. The oxidized adsorbate could be the radical cation of the Nheterocycle from the oligomers (stabilized by resonance), which could be regenerated by the recombination with the photoexcited electron (back electron transfer) or by reacting with suitable electron donors available in the medium.…”

Sustainable catalysts for efficient triazole synthesis: an immobilized triazine-based copper-NNN pincer complex on TiO2

“…20,21 The bandgap of P25 has been found to be around 3.0 to 3.2 eV which implies that the photoexcited electron/hole pairs on the oxide can only be generated via UV light irradiation. 22 For this reason, several efforts have been made to extend its optical absorption range from the UV to the visible light range to allow excitation by solar radiation. To this end, various modification methods have been applied to enhance the photocatalytic activity and performance of TiO 2 under solar-light irradiation.…”