Photocatalytic selective oxidation of phenol to produce dihydroxybenzenes in a TiO₂/UV system: Hydroxyl radical versus hole

Kangle LV, Xiaojia GUO, Xiaofeng WU, Qin LI, Wing Kei HO, Mei LI, Hengpeng YE, Dongyun DU

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

Photocatalytic oxidation plays an important role in organic synthesis. This research systematically studied the effect of reactive oxidation species (ROSs) such as surface-bounded hydroxyl radicals (·OHb), free hydroxyl radicals (·OHf), and hole (h⁺) on the photocatalytic selective oxidation of phenol in the TiO₂/UV system and its corresponding important chemical intermediates, dihydroxybenzenes. Experimental results showed that (1) the oxidation of phenol by hydroxyl radicals, whether in free (·OHf) or bounded states (·OHb), led mainly to the ortho- (catechol) and para-oriented hydroxy derivatives (hydroquinone), whereas the meta-oriented hydroxy derivative (resorcinol) became the main product when hole was used as the active species; (2) in naked TiO₂ suspensions, where ·OHb was the main ROSs, the selectivity of the catechol detected in the solution was much lower than that on the surface of the fluorinated TiO₂ system (TiO₂-F), where ·OHf served as the main ROSs. This finding can be attributed to the very strong catechol adsorption on the surface of naked TiO₂. However, this adsorption was severely inhibited in the presence of fluorine because of of the competitive adsorption between catechol and fluoride ions over TiO₂ photocatalyst; and (3) the hole oxidation of phenol provided a slower oxidation rate but a higher yield of dihydroxybenzenes compared with hydroxyl radical-mediated oxidation. Copyright © 2016 Elsevier B.V.
Original languageEnglish
Pages (from-to)405-411
JournalApplied Catalysis B: Environmental
Volume199
Early online dateJun 2016
DOIs
Publication statusPublished - Dec 2016

Fingerprint

hydroxyl radical
Phenol
Hydroxyl Radical
Phenols
phenol
oxidation
Oxidation
adsorption
Adsorption
Derivatives
Fluorine
fluorine
free radical
Photocatalysts
Free radicals
Fluorides
fluoride
Suspensions
Ions
catechol

Citation

Lv, K., Guo, X., Wu, X., Li, Q., Ho, W., Li, M., et al. (2016). Photocatalytic selective oxidation of phenol to produce dihydroxybenzenes in a TiO₂/UV system: Hydroxyl radical versus hole. Applied Catalysis B: Environmental, 199, 405-411.

Keywords

  • TiO₂
  • Photocatalytic oxidation
  • Selective oxidation
  • Phenol
  • Reactive oxygen species