Ceria-based catalysts for the production of H2 through the water-gas-shift reaction: Time-resolved XRD and XAFS studies

Xianqin Wang; José A. Rodriguez; Jonathan C. Hanson; Daniel Gamarra; Arturo Martínez-Arias; Marcos Fernández-García

doi:10.1007/s11244-008-9071-6

Ceria-based catalysts for the production of H₂ through the water-gas-shift reaction: Time-resolved XRD and XAFS studies

Xianqin Wang, José A. Rodriguez, Jonathan C. Hanson, Daniel Gamarra, Arturo Martínez-Arias, Marcos Fernández-García

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

37 Scopus citations

Abstract

Hydrogen is a potential alternate energy source for satisfying many of our energy needs. In this work, we studied H₂ production from the water-gas-shift (WGS) reaction over Ce_1-xCu_xO₂ catalysts, prepared with a novel microemulsion method, using two synchrotron-based techniques: time-resolved X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The results are compared with those reported for conventional CuO_x/CeO₂ and AuO_x/CeO ₂ catalysts obtained through impregnation of ceria. For the fresh Ce_1-xCu_xO₂ catalysts, the results of XAFS measurements at the Cu K-edge indicate that Cu is in an oxidation state higher than in CuO. Nevertheless, under WGS reaction conditions the Ce _1-xCu_xO₂ catalysts undergo reduction and the active phase contains very small particles of metallic Cu and CeO_2-x. Time-resolved XRD and XAFS results also indicate that Cu^δ+ and Au^δ+ species present in fresh CuO_x/CeO₂ and AuO_x/CeO₂ catalysts do not survive above 200 °C under the WGS conditions. In all these systems, the ceria lattice displayed a significant increase after exposure to CO and a decrease in H₂O, indicating that CO reduced ceria while H₂O oxidized it. Our data suggest that H₂O dissociation occurred on the O_vacancy sites or the Cu-O_vacancy and Au-O_vacancy interfaces. The rate of H₂ generation by a Ce_0.95Cu_0.05O ₂ catalyst was comparable to that of a 5 wt% CuO_x/CeO ₂ catalyst and much bigger than those of pure ceria or CuO.

Original language	English (US)
Pages (from-to)	81-88
Number of pages	8
Journal	Topics in Catalysis
Volume	49
Issue number	1-2
DOIs	https://doi.org/10.1007/s11244-008-9071-6
State	Published - Jul 2008
Externally published	Yes

All Science Journal Classification (ASJC) codes

Catalysis
General Chemistry

Keywords

Ceria catalysts
Copper catalysts
Gold catalysts
Hydrogen
In situ characterization
Water-gas shift reaction
X-ray absorption fine structure
X-ray diffraction

Access to Document

10.1007/s11244-008-9071-6

Cite this

@article{c354b52bb3284367a5cd3af9e47a787d,

title = "Ceria-based catalysts for the production of H2 through the water-gas-shift reaction: Time-resolved XRD and XAFS studies",

abstract = "Hydrogen is a potential alternate energy source for satisfying many of our energy needs. In this work, we studied H2 production from the water-gas-shift (WGS) reaction over Ce1-xCuxO2 catalysts, prepared with a novel microemulsion method, using two synchrotron-based techniques: time-resolved X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The results are compared with those reported for conventional CuOx/CeO2 and AuOx/CeO 2 catalysts obtained through impregnation of ceria. For the fresh Ce1-xCuxO2 catalysts, the results of XAFS measurements at the Cu K-edge indicate that Cu is in an oxidation state higher than in CuO. Nevertheless, under WGS reaction conditions the Ce 1-xCuxO2 catalysts undergo reduction and the active phase contains very small particles of metallic Cu and CeO2-x. Time-resolved XRD and XAFS results also indicate that Cuδ+ and Auδ+ species present in fresh CuOx/CeO2 and AuOx/CeO2 catalysts do not survive above 200 °C under the WGS conditions. In all these systems, the ceria lattice displayed a significant increase after exposure to CO and a decrease in H2O, indicating that CO reduced ceria while H2O oxidized it. Our data suggest that H2O dissociation occurred on the Ovacancy sites or the Cu-Ovacancy and Au-Ovacancy interfaces. The rate of H2 generation by a Ce0.95Cu0.05O 2 catalyst was comparable to that of a 5 wt% CuOx/CeO 2 catalyst and much bigger than those of pure ceria or CuO.",

keywords = "Ceria catalysts, Copper catalysts, Gold catalysts, Hydrogen, In situ characterization, Water-gas shift reaction, X-ray absorption fine structure, X-ray diffraction",

author = "Xianqin Wang and Rodriguez, {Jos{\'e} A.} and Hanson, {Jonathan C.} and Daniel Gamarra and Arturo Mart{\'i}nez-Arias and Marcos Fern{\'a}ndez-Garc{\'i}a",

note = "Funding Information: Acknowledgements The research carried out at the Chemistry Department of Brookhaven National Laboratory was financed through Contract No. DE-AC02-98CH10086 with the US Department of Energy, Division of Chemical Sciences. The NSLS is supported by the Divisions of Materials and Chemical Sciences of DOE. Work at the {\textquoteleft}{\textquoteleft}Instituto de Cat{\'a}lisis (CSIC){\textquoteright}{\textquoteright} was done with financial support from CICYT (Contracts No. CTQ2004-03409/BQU and MAT2003-03925); D. G. thanks the FPI program of the Ministerio de Educaci{\'o}n y Ciencia for a PhD grant. Thanks are due to Syed Khalid and Wolfgang Caliebe for their help and facilities given in the operation of beamlines X18B and X19A. The authors are grateful to M. Stephanopoulos for many useful conversations about the behavior of ceria-based catalysts during the water-gas shift.",

year = "2008",

month = jul,

doi = "10.1007/s11244-008-9071-6",

language = "English (US)",

volume = "49",

pages = "81--88",

journal = "Topics in Catalysis",

issn = "1022-5528",

publisher = "Springer Netherlands",

number = "1-2",

}

TY - JOUR

T1 - Ceria-based catalysts for the production of H2 through the water-gas-shift reaction

T2 - Time-resolved XRD and XAFS studies

AU - Wang, Xianqin

AU - Rodriguez, José A.

AU - Hanson, Jonathan C.

AU - Gamarra, Daniel

AU - Martínez-Arias, Arturo

AU - Fernández-García, Marcos

N1 - Funding Information: Acknowledgements The research carried out at the Chemistry Department of Brookhaven National Laboratory was financed through Contract No. DE-AC02-98CH10086 with the US Department of Energy, Division of Chemical Sciences. The NSLS is supported by the Divisions of Materials and Chemical Sciences of DOE. Work at the ‘‘Instituto de Catálisis (CSIC)’’ was done with financial support from CICYT (Contracts No. CTQ2004-03409/BQU and MAT2003-03925); D. G. thanks the FPI program of the Ministerio de Educación y Ciencia for a PhD grant. Thanks are due to Syed Khalid and Wolfgang Caliebe for their help and facilities given in the operation of beamlines X18B and X19A. The authors are grateful to M. Stephanopoulos for many useful conversations about the behavior of ceria-based catalysts during the water-gas shift.

PY - 2008/7

Y1 - 2008/7

N2 - Hydrogen is a potential alternate energy source for satisfying many of our energy needs. In this work, we studied H2 production from the water-gas-shift (WGS) reaction over Ce1-xCuxO2 catalysts, prepared with a novel microemulsion method, using two synchrotron-based techniques: time-resolved X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The results are compared with those reported for conventional CuOx/CeO2 and AuOx/CeO 2 catalysts obtained through impregnation of ceria. For the fresh Ce1-xCuxO2 catalysts, the results of XAFS measurements at the Cu K-edge indicate that Cu is in an oxidation state higher than in CuO. Nevertheless, under WGS reaction conditions the Ce 1-xCuxO2 catalysts undergo reduction and the active phase contains very small particles of metallic Cu and CeO2-x. Time-resolved XRD and XAFS results also indicate that Cuδ+ and Auδ+ species present in fresh CuOx/CeO2 and AuOx/CeO2 catalysts do not survive above 200 °C under the WGS conditions. In all these systems, the ceria lattice displayed a significant increase after exposure to CO and a decrease in H2O, indicating that CO reduced ceria while H2O oxidized it. Our data suggest that H2O dissociation occurred on the Ovacancy sites or the Cu-Ovacancy and Au-Ovacancy interfaces. The rate of H2 generation by a Ce0.95Cu0.05O 2 catalyst was comparable to that of a 5 wt% CuOx/CeO 2 catalyst and much bigger than those of pure ceria or CuO.

AB - Hydrogen is a potential alternate energy source for satisfying many of our energy needs. In this work, we studied H2 production from the water-gas-shift (WGS) reaction over Ce1-xCuxO2 catalysts, prepared with a novel microemulsion method, using two synchrotron-based techniques: time-resolved X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The results are compared with those reported for conventional CuOx/CeO2 and AuOx/CeO 2 catalysts obtained through impregnation of ceria. For the fresh Ce1-xCuxO2 catalysts, the results of XAFS measurements at the Cu K-edge indicate that Cu is in an oxidation state higher than in CuO. Nevertheless, under WGS reaction conditions the Ce 1-xCuxO2 catalysts undergo reduction and the active phase contains very small particles of metallic Cu and CeO2-x. Time-resolved XRD and XAFS results also indicate that Cuδ+ and Auδ+ species present in fresh CuOx/CeO2 and AuOx/CeO2 catalysts do not survive above 200 °C under the WGS conditions. In all these systems, the ceria lattice displayed a significant increase after exposure to CO and a decrease in H2O, indicating that CO reduced ceria while H2O oxidized it. Our data suggest that H2O dissociation occurred on the Ovacancy sites or the Cu-Ovacancy and Au-Ovacancy interfaces. The rate of H2 generation by a Ce0.95Cu0.05O 2 catalyst was comparable to that of a 5 wt% CuOx/CeO 2 catalyst and much bigger than those of pure ceria or CuO.

KW - Ceria catalysts

KW - Copper catalysts

KW - Gold catalysts

KW - Hydrogen

KW - In situ characterization

KW - Water-gas shift reaction

KW - X-ray absorption fine structure

KW - X-ray diffraction

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U2 - 10.1007/s11244-008-9071-6

DO - 10.1007/s11244-008-9071-6

M3 - Article

AN - SCOPUS:47549115848

SN - 1022-5528

VL - 49

SP - 81

EP - 88

JO - Topics in Catalysis

JF - Topics in Catalysis

IS - 1-2

ER -