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Highly Enhanced Concentration and Stability of Reactive Ce^3+ on Doped CeO_2 Surface Revealed In Operando

Chueh, William C. and McDaniel, Anthony H. and Grass, Michael E. and Hao, Yong and Jabeen, Naila and Liu, Zhi and Haile, Sossina M. and McCarty, Kevin F. and Bluhm, Hendrik and El Gabaly, Farid (2012) Highly Enhanced Concentration and Stability of Reactive Ce^3+ on Doped CeO_2 Surface Revealed In Operando. Chemistry of Materials, 24 (10). pp. 1876-1882. ISSN 0897-4756. doi:10.1021/cm300574v.

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Trivalent cerium ions in CeO_2 are the key active species in a wide range of catalytic and electro-catalytic reactions. We employed ambient pressure X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy to quantify simultaneously the concentration of the reactive Ce^3+ species on the surface and in the bulk of Sm-doped CeO_2(100) in hundreds of millitorr of H2–H2O gas mixtures. Under relatively oxidizing conditions, when the bulk cerium is almost entirely in the 4+ oxidation state, the surface concentration of the reduced Ce^3+ species can be over 180 times the bulk concentration. Furthermore, in stark contrast to the bulk, the surface’s 3+ oxidation state is also highly stable, with concentration almost independent of temperature and oxygen partial pressure. Our thermodynamic measurements reveal that the difference between the bulk and surface partial molar entropies plays a key role in this stabilization. The high concentration and stability of reactive surface Ce^3+ over wide ranges of temperature and oxygen partial pressure may be responsible for the high activity of doped ceria in many pollution-control and energy-conversion reactions, under conditions at which Ce^3+ is not abundant in the bulk.

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Haile, Sossina M.0000-0002-5293-6252
Additional Information:© 2012 American Chemical Society. Published In Issue May 22, 2012: Article ASAP: May 07, 2012; Just Accepted Manuscript: April 25, 2012; Received: February 21, 2012; Revised: April 13, 2012. This research was supported by the U.S. Department of Energy through the Sandia Laboratory Directed Research and Development program under Contract DE-AC04-94AL85000. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231. Additional support was provided by the NSF through Award DMR-0604004 and through the Caltech Center for the Science and Engineering of Materials, a Materials Research Science and Engineering Center (DMR-052056). W.C.C. was also supported by an appointment to the Sandia National Laboratories Truman Fellowship in National Security Science and Engineering. The authors are grateful to Norm Bartelt for insightful discussion and also acknowledge Carol Garland for her assistance with electron microscopy and Taesik Oh for his assistance with experiments at the Advanced Light Source.
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC04-94AL85000
Department of Energy (DOE)DE-AC02-05CH11231
Sandia National Laboratories Truman FellowshipUNSPECIFIED
Subject Keywords:ceria; ambient pressure XPS; catalysis; electrochemistry
Issue or Number:10
Record Number:CaltechAUTHORS:20120618-102638412
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Official Citation:Highly Enhanced Concentration and Stability of Reactive Ce3+ on Doped CeO2 Surface Revealed In Operando William C. Chueh, Anthony H. McDaniel, Michael E. Grass, Yong Hao, Naila Jabeen, Zhi Liu, Sossina M. Haile, Kevin F. McCarty, Hendrik Bluhm, and Farid El Gabaly Chemistry of Materials 2012 24 (10), 1876-1882
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31927
Deposited By: Jason Perez
Deposited On:18 Jun 2012 22:59
Last Modified:09 Nov 2021 20:02

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