Co-adsorption of oxygen and formic acid on rutile TiO2 (110) studied by infrared reflection-absorption spectroscopy

SURFACE SCIENCE

卷:663

Article

Mattsson, Andreas¹  Osterlund, Lars¹ 

[1] Uppsala Univ, Angstrom Lab, Dept Engn Sci, POB 534, SE-75121 Uppsala, Sweden

关键词: TiO2;    Infrared reflection absorption spectroscopy;    Formic acid;    Bicarbonate;   

DOI  :  10.1016/j.susc.2017.04.012

来源: Elsevier

【 摘 要 】

Adsorption of formic acid and co-adsorption with oxygen have been investigated on the rutile TiO2(110) surface using p- and s-polarized infrared reflection-absorption spectroscopy (IRRAS) at O-2 exposures between 45 L to 8100 L and at temperatures between 273 K and 343 K. On the clean surface formic acid dissociates into a formate ion (formate) and a proton. Formate binds to two five-fold coordinated Ti atoms in the troughs along the [001] direction, and the proton binds to neighboring bridging O atoms. Exposure of adsorbed formate to O-2 leads to a decrease in the asymmetric v(as)(OCO) band at 1532 cm(-1) and to the concomitant formation of a new vibration band at 1516 cm(-1). From the s-and p-polarized IRRAS measurements performed at different O-2 exposures, surface pre-treatments and substrate temperatures, and by comparisons with previous reports, we conclude that the new species is a bidentate surface hydrogen carbonate, which is formed by reaction between formate and oxygen adatoms on the surface. The sigma(v) reflection plane of the surface hydrogen carbonate molecule is oriented along the [001] direction, i.e. the same direction as the adsorbed formate molecule. On the clean TiO2(110) surface exposed to O-2 prior to formic acid adsorption, similar results are obtained. The reaction rate to form surface hydrogen carbonate from formate is found to follow first-order kinetics, with an apparent activation energy of E-r=0.25 eV.

【 授权许可】

Free