Surface Chemistry of Formaldehyde on Rutile TiO2(110) Surface: Photocatalysis vs Thermal-Catalysis

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• 作者：Qing Yuan ; Zongfang Wu ; Yuekang Jin ; Feng Xiong ; Weixin Huang
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：September 4, 2014
• 年：2014
• 卷：118
• 期：35
• 页码：20420-20428
• 全文大小：589K
• ISSN：1932-7455

文摘

The photocatalytic surface reactions of formaldehyde (HCHO) on rutile TiO₂(110) surface were studied by means of thermal desorption spectroscopy and X-ray photoelectron spectroscopy and compared with its thermally catalytic surface reactions. Thermally catalytic surface reactions of formaldehyde on rutile TiO₂(110) surface are dominated by the carbon鈥揷arbon bond formation reaction of HCHO adsorbed at oxygen vacancies to produce C₂H₄ via a diolate (鈭扥CH₂CH₂O鈭? surface intermediate. During the photocatalytic surface reactions, HCHO adsorbed at the Ti_5c sites of rutile TiO₂(110) surface is photocatalytically oxidized to a transient formyl (HCO) species that facilely transforms to adsorbed formate (HCOO) species. HCOO species and HCHO adsorbed at oxygen vacancies undergo novel surface reactions to produce CO, C₂H₄, and CH₃OH at elevated temperatures whose mechanisms were successfully identified. The healing of bridging oxygen vacancies on rutile TiO₂(110) surface by preadsorption of water suppresses the oxygen vacancy-mediated coupling reaction of formaldehyde but does not affect its photocatalytic surface reactions. These results not only greatly deepen the fundamental understanding of photochemistry of formaldehyde on TiO₂ surface but also demonstrate novel surface reactions of organic functional groups formed by the combined photocatalytic and thermally catalytic reactions of formaldehyde on oxide surfaces.