Transient studies of the mechanisms of CO oxidation over Au/TiO2 using time-resolved FTIR spectroscopy and product analysis

Bong Kyu Chang; Ben W. Jang; Sheng Dai; Steven H. Overbury

doi:10.1016/j.jcat.2005.10.006

Transient studies of the mechanisms of CO oxidation over Au/TiO₂ using time-resolved FTIR spectroscopy and product analysis

Bong Kyu Chang, Ben W. Jang, Sheng Dai, Steven H. Overbury

Chemical Sciences Division

Research output: Contribution to journal › Article › peer-review

48 Scopus citations

Abstract

Transient studies on the oxidation of CO over Au/TiO₂ have been performed at 243-363 K using a time-resolved fast-scanning Fourier transform infrared (FTIR) spectrometer coupled with a quadrupole mass spectrometer. Different CO-O₂ interactions were performed by stepping CO into a steady-state He flow, O₂ into a steady-state CO flow, CO into a steady-state O₂ flow, and CO/O₂ into an He flow. The CO oxidation reaction occurs at all temperature ranges investigated whether CO is preadsorbed or O₂ is preadsorbed, indicating that there is no competition between CO and O₂ for adsorption at a temperature range of 243-363 K (noncompetitive adsorption). It suggests that CO and O₂ adsorption occurs on two different types of sites. When there is no O ₂ present in step feed (i.e., step CO into He), CO immediately builds up on the surface (rapid adsorption of CO) and desorbs slowly after cutting off CO flow. However, when O₂ is present in the step feed (i.e., step CO/O₂ into He), adsorbed CO reacts with adsorbed oxygen immediately (fast surface reaction), whereas CO₂ product desorption monitored by mass spectroscopy appears to be very slow. Slow desorption of CO₂ product is claimed to be the rate-limiting step of CO oxidation over Au/TiO ₂ at a temperature range of 243-273 K.

Original language	English
Pages (from-to)	392-400
Number of pages	9
Journal	Journal of Catalysis
Volume	236
Issue number	2
DOIs	https://doi.org/10.1016/j.jcat.2005.10.006
State	Published - Dec 10 2005

Funding

The research is supported by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC. BKC is sponsored by an appointment to the Oak Ridge National Laboratory Postdoctoral Research Associates Program administered jointly by the Oak Ridge Institute for Science and Education and Oak Ridge National Laboratory.

Funders	Funder number
Office of Basic Energy Sciences
U.S. Department of Energy	DE-AC05-00OR22725
Oak Ridge National Laboratory
Oak Ridge Institute for Science and Education
Chemical Sciences, Geosciences, and Biosciences Division

Keywords

Adsorption
Au/TiO catalyst
CO catalytic oxidation
Desorption
FTIR
Mass spectrometry
Operando spectroscopy
Rate-limiting step

Access to Document

10.1016/j.jcat.2005.10.006

Cite this

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title = "Transient studies of the mechanisms of CO oxidation over Au/TiO2 using time-resolved FTIR spectroscopy and product analysis",

abstract = "Transient studies on the oxidation of CO over Au/TiO2 have been performed at 243-363 K using a time-resolved fast-scanning Fourier transform infrared (FTIR) spectrometer coupled with a quadrupole mass spectrometer. Different CO-O2 interactions were performed by stepping CO into a steady-state He flow, O2 into a steady-state CO flow, CO into a steady-state O2 flow, and CO/O2 into an He flow. The CO oxidation reaction occurs at all temperature ranges investigated whether CO is preadsorbed or O2 is preadsorbed, indicating that there is no competition between CO and O2 for adsorption at a temperature range of 243-363 K (noncompetitive adsorption). It suggests that CO and O2 adsorption occurs on two different types of sites. When there is no O 2 present in step feed (i.e., step CO into He), CO immediately builds up on the surface (rapid adsorption of CO) and desorbs slowly after cutting off CO flow. However, when O2 is present in the step feed (i.e., step CO/O2 into He), adsorbed CO reacts with adsorbed oxygen immediately (fast surface reaction), whereas CO2 product desorption monitored by mass spectroscopy appears to be very slow. Slow desorption of CO2 product is claimed to be the rate-limiting step of CO oxidation over Au/TiO 2 at a temperature range of 243-273 K.",

keywords = "Adsorption, Au/TiO catalyst, CO catalytic oxidation, Desorption, FTIR, Mass spectrometry, Operando spectroscopy, Rate-limiting step",

author = "Chang, {Bong Kyu} and Jang, {Ben W.} and Sheng Dai and Overbury, {Steven H.}",

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AU - Chang, Bong Kyu

AU - Jang, Ben W.

AU - Dai, Sheng

AU - Overbury, Steven H.

PY - 2005/12/10

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N2 - Transient studies on the oxidation of CO over Au/TiO2 have been performed at 243-363 K using a time-resolved fast-scanning Fourier transform infrared (FTIR) spectrometer coupled with a quadrupole mass spectrometer. Different CO-O2 interactions were performed by stepping CO into a steady-state He flow, O2 into a steady-state CO flow, CO into a steady-state O2 flow, and CO/O2 into an He flow. The CO oxidation reaction occurs at all temperature ranges investigated whether CO is preadsorbed or O2 is preadsorbed, indicating that there is no competition between CO and O2 for adsorption at a temperature range of 243-363 K (noncompetitive adsorption). It suggests that CO and O2 adsorption occurs on two different types of sites. When there is no O 2 present in step feed (i.e., step CO into He), CO immediately builds up on the surface (rapid adsorption of CO) and desorbs slowly after cutting off CO flow. However, when O2 is present in the step feed (i.e., step CO/O2 into He), adsorbed CO reacts with adsorbed oxygen immediately (fast surface reaction), whereas CO2 product desorption monitored by mass spectroscopy appears to be very slow. Slow desorption of CO2 product is claimed to be the rate-limiting step of CO oxidation over Au/TiO 2 at a temperature range of 243-273 K.

AB - Transient studies on the oxidation of CO over Au/TiO2 have been performed at 243-363 K using a time-resolved fast-scanning Fourier transform infrared (FTIR) spectrometer coupled with a quadrupole mass spectrometer. Different CO-O2 interactions were performed by stepping CO into a steady-state He flow, O2 into a steady-state CO flow, CO into a steady-state O2 flow, and CO/O2 into an He flow. The CO oxidation reaction occurs at all temperature ranges investigated whether CO is preadsorbed or O2 is preadsorbed, indicating that there is no competition between CO and O2 for adsorption at a temperature range of 243-363 K (noncompetitive adsorption). It suggests that CO and O2 adsorption occurs on two different types of sites. When there is no O 2 present in step feed (i.e., step CO into He), CO immediately builds up on the surface (rapid adsorption of CO) and desorbs slowly after cutting off CO flow. However, when O2 is present in the step feed (i.e., step CO/O2 into He), adsorbed CO reacts with adsorbed oxygen immediately (fast surface reaction), whereas CO2 product desorption monitored by mass spectroscopy appears to be very slow. Slow desorption of CO2 product is claimed to be the rate-limiting step of CO oxidation over Au/TiO 2 at a temperature range of 243-273 K.

KW - Adsorption

KW - Au/TiO catalyst

KW - CO catalytic oxidation

KW - Desorption

KW - FTIR

KW - Mass spectrometry

KW - Operando spectroscopy

KW - Rate-limiting step

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