Exploring the photocatalytic conversion mechanism of gaseous formaldehyde degradation on TiO2-X-OV surface

Xinwei LI, Haiwei LI, Yu HUANG, Junji CAO, Tingting HUANG, Rong LI, Qian ZHANG, Shun-cheng LEE, Wingkei HO

Research output: Contribution to journalArticlespeer-review

2 Citations (Scopus)

Abstract

To understand the conversion mechanism of photocatalytic gaseous formaldehyde (HCHO) degradation, strontium (Sr)-doped TiO2–x–OV catalysts was designed and synthesized in this study, with comparable HCHO removal performance. Our results proved that foreign-element doping reduced Ti4+ to the lower oxidation state Ti(4– x)+, and that the internal charge kinetics was largely facilitated by the unbalanced electron distribution. Oxygen vacancies (OVs) were developed spontaneously to realize an electron-localized phenomenon in TiO2–x–OV, thereby boosting O2 adsorption and activation for the enhanced generation of reactive oxygen species (ROS). At the chemisorption stage, in-situ DRIFTS spectra and density functional theory calculation results revealed that surface adsorbed O2 (Oads) and lattice O (Olat) engaged in the isomerisation of HCHO to dioxymethylene (DOM) on TiO2–x–OV and TiO2, respectively. Time-resolved DRIFTS spectra under light irradiation revealed that the DOM was then converted to formate and thoroughly oxidized to CO2 and H2O in TiO2–x–OV. While bicarbonate byproducts were detected from DOM hydroxylation or possible side conversion of CO2 in TiO2, owing to insufficient consumption of surface hydroxyl. Our study enhances the understanding on the photocatalytic oxidation of HCHO, thereby promoting the practical application in indoor air purification. Copyright © 2021 Elsevier B.V. All rights reserved.

Original languageEnglish
Article number127217
JournalJournal of Hazardous Materials
Volume424
Issue numberPart A
Early online dateSep 2021
DOIs
Publication statusE-pub ahead of print - Sep 2021

Citation

Li, X., Li, H., Huang, Y., Cao, J., Huang, T., Li, R., . . . Ho, W. (2022). Exploring the photocatalytic conversion mechanism of gaseous formaldehyde degradation on TiO₂₋ₓ-OV surface. Journal of Hazardous Materials, 424(Part A). Retrieved from https://doi.org/10.1016/j.jhazmat.2021.127217

Keywords

  • Formaldehyde
  • Photocatalytic degradation
  • Oxygen vacancies
  • Quantum efficiency
  • Intermediates

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