Infrared Spectroscopic Study of Adsorption and Reactions of Glyoxylic Acid on TiO2

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• 作者：Chia-Hsun Ho ; Chun-Yi Shieh ; Chien-Lin Tseng ; Jong-Liang Lin
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：November 20, 2008
• 年：2008
• 卷：112
• 期：46
• 页码：18134-18140
• 全文大小：236K
• 年卷期：v.112,no.46(November 20, 2008)
• ISSN：1932-7455

文摘

Fourier transform infrared spectroscopy has been employed to investigate the adsorption, thermal reactions, and photodegradation of glyoxylic acid on TiO₂ in a gas−solid system. Glyoxylic acid may exist on TiO₂ at 35 °C with several dissociative adsorption forms, through the interaction of the carboxyl group or the diol group derived from carbonyl transformation. CO, CO₂, HCOO (formate), and CH₃O (methoxy) are found to be the thermal reaction products. A C−C bond scission pathway is proposed for the formation of CH₃O via −OCH₂O− (dioxymethylene), which can undergo self oxidation−reduction. However, another possible route producing oxalic acid or oxalate is not important. Moreover, O₂ has no effect on the decomposition of the surface glyoxylic acid and on the formation temperature of the thermal reaction products. In the photochemistry of glyoxylic acid on TiO₂ irradiated at 400 nm, it produces CO₂, carbonate, and HCOO. O₂ can enhance the formation of CO₂ and carbonate species. The ¹⁸O₂ isotopic study shows that the CO₂ and carbonates formed in the initial photoirradiation stage (≤10 min) may only contain a small amount of ¹⁸O. The role dioxygen may play in the initial photodecomposition of glyoxylic acid on TiO₂ is to capture the photogenerated electrons, increasing the lifetime of holes and thus the photooxidation efficiency, but hardly directly participating in the product formation.