In situ transient FTIR and XANES studies of the evolution of surface species in CO oxidation on Au/TiO2.
The adsorption of CO and its reaction with oxygen were investigated using a combination of in situ Fourier transform infrared spectroscopy, step response measurements in a microreactor, (18)O isotopic labeling, and X-ray absorption near edge structure spectroscopy. An as-prepared sample in which Au is present as a surface oxyhydroxy complex does not adsorb CO. On an activated sample in which only metallic Au is detected, 0.18 +/- 0.03 mol CO/(mol Au) are adsorbed on Au at -60 degrees C, which shows an IR band at 2090 cm(-1). When oxygen is present in the gas phase, this species reacts with a turnover rate of 1.4 +/- 0.2 mol CO(mol Au min)(-1), which is close to the steady-state turnover rate. In contrast, there is a very small quantity of adsorbed oxygen on Au. A small IR peak at 1242 cm(-1) appears when an activated sample is exposed to CO. It reacts rapidly with oxygen and is shifted to 1236 cm(-1) if (18)O is used. It is assigned to the possible intermediate hydroxycarbonyl.
Henao
Juan D
JD
Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208-3120, USA.
Caputo
Tiziana
T
Yang
Jeff H
JH
Kung
Mayfair C
MC
Kung
Harold H
HH
D000327:Adsorption; D002248:Carbon Monoxide / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D010084:Oxidation-Reduction; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013057:Spectrum Analysis / Q000379:methods; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D014965:X-Rays
C009495:titanium dioxide; D006046:Gold; D002248:Carbon Monoxide; D014025:Titanium