Identification of Binding Sites for Acetaldehyde Adsorption on Titania Nanorod Surfaces Using CIMS

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• 作者：Daniel Finkelstein-Shapiro ; Avram M. Buchbinder ; Baiju Vijayan ; Kaustava Bhattacharyya ; Eric Weitz ; Franz M. Geiger ; Kimberly A. Gray
• 刊名：Langmuir
• 出版年：2011
• 出版时间：December 20, 2011
• 年：2011
• 卷：27
• 期：24
• 页码：14842-14848
• 全文大小：909K
• 年卷期：v.27,no.24(December 20, 2011)
• ISSN：1520-5827

文摘

The interaction of acetaldehyde with TiO₂ nanorods has been studied under low pressures (acetaldehyde partial pressure range 10^鈥?鈥?0^鈥? Torr) using chemical ionization mass spectrometry (CIMS). We quantitatively separate irreversible adsorption, reversible adsorption, and an uptake of acetaldehyde assigned to a thermally activated surface reaction. We find that, at room temperature and 1.2 Torr total pressure, 2.1 卤 0.4 molecules/nm² adsorb irreversibly, but this value exhibits a sharp decrease as the analyte partial pressure is lowered below 4 脳 10^鈥? Torr, regardless of exposure time. The number of reversible binding sites at saturation amounts to 0.09 卤 0.02 molecules/nm² with a free energy of adsorption of 43.8 卤 0.2 kJ/mol. We complement our measurements with FTIR spectroscopy and identify the thermal dark reaction as a combination of an aldol condensation and an oxidative adsorption that converts acetaldehyde to acetate or formate and CO, at a measured combined initial rate of 7 卤 1 脳 10^鈥? molecules/nm² s. By characterizing binding to different types of sites under dark conditions in the absence of oxygen and gas phase water, we set the stage to analyze site-specific photoefficiencies involved in the light-assisted mineralization of acetaldehyde to CO₂.