Decomposition pathways of glycolic acid on titanium dioxide

Chia Hsun Ho, Chun Yi Shieh, Chien Lin Tseng, Yi Kwan Chen, Jong Liang Lin

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Fourier-transformed infrared spectroscopy has been employed to study the adsorption, thermal reactions and photodegradation of glycolic acid (HOCH2COOH) on TiO2 in a gas-solid system. The intriguing research focus is the reactivity and evolution of the two functional groups. Glycolic acid can exist on TiO2 at 35 °C in two dissociative adsorption forms, OCH2COOH and HOCH2COO, which are derived from hydrogen loss of the COH and COOH groups, respectively. Heating the surface to a temperature higher than ∼100 °C causes a largely enhanced carbonyl stretching band at ∼1750 cm-1, indicative of oxidation of the OCH2 groups of the surface glycolic acid molecules. This chemical process is supported by the adsorption of glyoxylic acid (HCOCOOH) on TiO2. As the surface temperature is further increased to 200 °C or higher, formate (HCOO) and methoxy (CH3O) are produced. Their formation is proposed via dioxymethylene (OCH2O) intermediate. CO and CO2 are found to be the final thermal products. Photoirradiation of a TiO2 surface covered with glycolic acid at ∼325 nm leads to its decomposition, generating CO2, CH3O, HCOO and carbonate species. O2 is found to promote the photochemical reactions of glycolic acid on TiO2 to form CO2, HCOO and carbonates. O2 may play a role hampering recombination of photogenerated electron-hole pairs and participating in the formation of CO2 and HCOO.

Original languageEnglish
Pages (from-to)150-157
Number of pages8
JournalJournal of Catalysis
Volume261
Issue number2
DOIs
Publication statusPublished - 2009 Jan 25

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Physical and Theoretical Chemistry

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