CO oxidation on Au/FePO4 catalyst: Reaction pathways and nature of Au sites

Meijun Li; Zili Wu; Zhen Ma; Viviane Schwartz; David R. Mullins; Sheng Dai; Steven H. Overbury

doi:10.1016/j.jcat.2009.05.019

CO oxidation on Au/FePO₄ catalyst: Reaction pathways and nature of Au sites

Meijun Li, Zili Wu, Zhen Ma, Viviane Schwartz, David R. Mullins, Sheng Dai, Steven H. Overbury

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

59 Scopus citations

Abstract

In situ FTIR spectroscopy coupled with downstream mass spectrometry has been used to clarify the pathways for room temperature (rt) CO oxidation over iron phosphate-supported Au catalyst. The charge state of Au on Au/FePO₄ after calcination, reduction, or under reaction conditions was assessed by both FTIR spectroscopy (CO probing) and X-ray absorption near edge spectroscopy (XANES). Results from both approaches show that cationic gold species dominate the surface after pretreatment in O₂ at 200 °C. A portion of the cationic gold on Au/FePO₄ can be reduced by the initial CO adsorption at rt, and subsequently repeated CO exposures do not reduce the remaining cationic Au. FTIR and Raman results from cycled CO reduction and O₂ reoxidation of Au/FePO₄ indicate that there are active structural oxygen species on the surface of Au/FePO₄that can be consumed by CO and then replenished by gaseous O₂ at rt. Au activates both CO and O₂ so that the FePO₄ support can undergo reduction (by CO) and reoxidation (by O₂) cycles. The results of CO oxidation with labeled ¹⁸O₂ suggest the operation of two parallel reaction pathways at rt: (1) a redox pathway in which FePO₄ supplies active oxygen and (2) a direct pathway on metallic Au, via either Langmuir-Hinshelwood or Eley-Rideal mechanism, in which gas phase O₂ provides the active oxygen.

Original language	English
Pages (from-to)	98-105
Number of pages	8
Journal	Journal of Catalysis
Volume	266
Issue number	1
DOIs	https://doi.org/10.1016/j.jcat.2009.05.019
State	Published - Aug 15 2009

Funding

This work was sponsored by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, US Department of Energy, under Contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC. A portion of this research was done using facilities at the Center for Nanophase Materials Sciences. XANES measurements were performed at the National Synchrotron Light Source, Brookhaven National Laboratory supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886, and using facilities of the Synchrotron Catalysis Consortium, supported by US Department of Energy Grant No. DE-FG02-05ER15688.

Funders	Funder number
U.S. Department of Energy	DE-AC05-00OR22725
Office of Science	DE-AC02-98CH10886, DE-FG02-05ER15688
Basic Energy Sciences
Oak Ridge National Laboratory
Chemical Sciences, Geosciences, and Biosciences Division

Keywords

Au catalyst
CO adsorption
Catalytic CO oxidation
FTIR
FePO
Iron phosphate
Mechanism
Raman spectroscopy
Redox
XANES

Access to Document

10.1016/j.jcat.2009.05.019

Cite this

@article{fe4dec4dcf194fdb8cca81951120879e,

title = "CO oxidation on Au/FePO4 catalyst: Reaction pathways and nature of Au sites",

abstract = "In situ FTIR spectroscopy coupled with downstream mass spectrometry has been used to clarify the pathways for room temperature (rt) CO oxidation over iron phosphate-supported Au catalyst. The charge state of Au on Au/FePO4 after calcination, reduction, or under reaction conditions was assessed by both FTIR spectroscopy (CO probing) and X-ray absorption near edge spectroscopy (XANES). Results from both approaches show that cationic gold species dominate the surface after pretreatment in O2 at 200 °C. A portion of the cationic gold on Au/FePO4 can be reduced by the initial CO adsorption at rt, and subsequently repeated CO exposures do not reduce the remaining cationic Au. FTIR and Raman results from cycled CO reduction and O2 reoxidation of Au/FePO4 indicate that there are active structural oxygen species on the surface of Au/FePO4that can be consumed by CO and then replenished by gaseous O2 at rt. Au activates both CO and O2 so that the FePO4 support can undergo reduction (by CO) and reoxidation (by O2) cycles. The results of CO oxidation with labeled 18O2 suggest the operation of two parallel reaction pathways at rt: (1) a redox pathway in which FePO4 supplies active oxygen and (2) a direct pathway on metallic Au, via either Langmuir-Hinshelwood or Eley-Rideal mechanism, in which gas phase O2 provides the active oxygen.",

keywords = "Au catalyst, CO adsorption, Catalytic CO oxidation, FTIR, FePO, Iron phosphate, Mechanism, Raman spectroscopy, Redox, XANES",

author = "Meijun Li and Zili Wu and Zhen Ma and Viviane Schwartz and Mullins, {David R.} and Sheng Dai and Overbury, {Steven H.}",

year = "2009",

month = aug,

day = "15",

doi = "10.1016/j.jcat.2009.05.019",

language = "English",

volume = "266",

pages = "98--105",

journal = "Journal of Catalysis",

issn = "0021-9517",

publisher = "Elsevier",

number = "1",

}

TY - JOUR

T1 - CO oxidation on Au/FePO4 catalyst

T2 - Reaction pathways and nature of Au sites

AU - Li, Meijun

AU - Wu, Zili

AU - Ma, Zhen

AU - Schwartz, Viviane

AU - Mullins, David R.

AU - Dai, Sheng

AU - Overbury, Steven H.

PY - 2009/8/15

Y1 - 2009/8/15

N2 - In situ FTIR spectroscopy coupled with downstream mass spectrometry has been used to clarify the pathways for room temperature (rt) CO oxidation over iron phosphate-supported Au catalyst. The charge state of Au on Au/FePO4 after calcination, reduction, or under reaction conditions was assessed by both FTIR spectroscopy (CO probing) and X-ray absorption near edge spectroscopy (XANES). Results from both approaches show that cationic gold species dominate the surface after pretreatment in O2 at 200 °C. A portion of the cationic gold on Au/FePO4 can be reduced by the initial CO adsorption at rt, and subsequently repeated CO exposures do not reduce the remaining cationic Au. FTIR and Raman results from cycled CO reduction and O2 reoxidation of Au/FePO4 indicate that there are active structural oxygen species on the surface of Au/FePO4that can be consumed by CO and then replenished by gaseous O2 at rt. Au activates both CO and O2 so that the FePO4 support can undergo reduction (by CO) and reoxidation (by O2) cycles. The results of CO oxidation with labeled 18O2 suggest the operation of two parallel reaction pathways at rt: (1) a redox pathway in which FePO4 supplies active oxygen and (2) a direct pathway on metallic Au, via either Langmuir-Hinshelwood or Eley-Rideal mechanism, in which gas phase O2 provides the active oxygen.

AB - In situ FTIR spectroscopy coupled with downstream mass spectrometry has been used to clarify the pathways for room temperature (rt) CO oxidation over iron phosphate-supported Au catalyst. The charge state of Au on Au/FePO4 after calcination, reduction, or under reaction conditions was assessed by both FTIR spectroscopy (CO probing) and X-ray absorption near edge spectroscopy (XANES). Results from both approaches show that cationic gold species dominate the surface after pretreatment in O2 at 200 °C. A portion of the cationic gold on Au/FePO4 can be reduced by the initial CO adsorption at rt, and subsequently repeated CO exposures do not reduce the remaining cationic Au. FTIR and Raman results from cycled CO reduction and O2 reoxidation of Au/FePO4 indicate that there are active structural oxygen species on the surface of Au/FePO4that can be consumed by CO and then replenished by gaseous O2 at rt. Au activates both CO and O2 so that the FePO4 support can undergo reduction (by CO) and reoxidation (by O2) cycles. The results of CO oxidation with labeled 18O2 suggest the operation of two parallel reaction pathways at rt: (1) a redox pathway in which FePO4 supplies active oxygen and (2) a direct pathway on metallic Au, via either Langmuir-Hinshelwood or Eley-Rideal mechanism, in which gas phase O2 provides the active oxygen.

KW - Au catalyst

KW - CO adsorption

KW - Catalytic CO oxidation

KW - FTIR

KW - FePO

KW - Iron phosphate

KW - Mechanism

KW - Raman spectroscopy

KW - Redox

KW - XANES

UR - http://www.scopus.com/inward/record.url?scp=67651180524&partnerID=8YFLogxK

U2 - 10.1016/j.jcat.2009.05.019

DO - 10.1016/j.jcat.2009.05.019

M3 - Article

AN - SCOPUS:67651180524

SN - 0021-9517

VL - 266

SP - 98

EP - 105

JO - Journal of Catalysis

JF - Journal of Catalysis

IS - 1

ER -