CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions

Handle URI:
http://hdl.handle.net/10754/597788
Title:
CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions
Authors:
Michalak, William D.; Krier, James M.; Alayoglu, Selim; Shin, Jae-Yoon; An, Kwangjin; Komvopoulos, Kyriakos; Liu, Zhi; Somorjai, Gabor A.
Abstract:
The barrier to CO oxidation on Pt catalysts is the strongly bound adsorbed CO, which inhibits O2 adsorption and hinders CO2 formation. Using reaction studies and in situ X-ray spectroscopy with colloidally prepared, monodisperse ∼2 nm Pt and PtSn nanoparticle catalysts, we show that the addition of Sn to Pt provides distinctly different reaction sites and a more efficient reaction mechanism for CO oxidation compared to pure Pt catalysts. To probe the influence of Sn, we intentionally poisoned the Pt component of the nanoparticle catalysts using a CO-rich atmosphere. With a reaction environment comprised of 100 Torr CO and 40 Torr O2 and a temperature range between 200 and 300 C, Pt and PtSn catalysts exhibited activation barriers for CO2 formation of 133 kJ/mol and 35 kJ/mol, respectively. While pure Sn is readily oxidized and is not active for CO oxidation, the addition of Sn to Pt provides an active site for O2 adsorption that is important when Pt is covered with CO. Sn oxide was identified as the active Sn species under reaction conditions by in situ ambient pressure X-ray photoelectron spectroscopy measurements. While chemical signatures of Pt and Sn indicated intermixed metallic components under reducing conditions, Pt and Sn were found to reversibly separate into isolated domains of Pt and oxidic Sn on the nanoparticle surface under reaction conditions of 100 mTorr CO and 40 mTorr O2 between temperatures of 200-275 C. Under these conditions, PtSn catalysts exhibited apparent reaction orders in O2 for CO 2 production that were 0.5 and lower with increasing partial pressures. These reaction orders contrast the first-order dependence in O 2 known for pure Pt. The differences in activation barriers, non-first-order dependence in O2, and the presence of a partially oxidized Sn indicate that the enhanced activity is due to a reaction mechanism that occurs at a Pt/Sn oxide interface present at the nanoparticle surface. © 2014 Published by Elsevier Inc.
Citation:
Michalak WD, Krier JM, Alayoglu S, Shin J-Y, An K, et al. (2014) CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions. Journal of Catalysis 312: 17–25. Available: http://dx.doi.org/10.1016/j.jcat.2014.01.005.
Publisher:
Elsevier BV
Journal:
Journal of Catalysis
Issue Date:
Apr-2014
DOI:
10.1016/j.jcat.2014.01.005
Type:
Article
ISSN:
0021-9517
Sponsors:
This research was funded by the U.S. Department of Energy, Office of Basic Energy Sciences, under contract no. DE-AC02-05CH11231. K.K. also acknowledges funding provided by the UCB-KAUST Academic Excellence Alliance (AEA) Program. This work was performed in part at the Molecular Foundry and the Advanced Light Source, beamline 9.3.2 of the Lawrence Berkeley National Laboratory. 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.
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DC FieldValue Language
dc.contributor.authorMichalak, William D.en
dc.contributor.authorKrier, James M.en
dc.contributor.authorAlayoglu, Selimen
dc.contributor.authorShin, Jae-Yoonen
dc.contributor.authorAn, Kwangjinen
dc.contributor.authorKomvopoulos, Kyriakosen
dc.contributor.authorLiu, Zhien
dc.contributor.authorSomorjai, Gabor A.en
dc.date.accessioned2016-02-25T12:56:43Zen
dc.date.available2016-02-25T12:56:43Zen
dc.date.issued2014-04en
dc.identifier.citationMichalak WD, Krier JM, Alayoglu S, Shin J-Y, An K, et al. (2014) CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions. Journal of Catalysis 312: 17–25. Available: http://dx.doi.org/10.1016/j.jcat.2014.01.005.en
dc.identifier.issn0021-9517en
dc.identifier.doi10.1016/j.jcat.2014.01.005en
dc.identifier.urihttp://hdl.handle.net/10754/597788en
dc.description.abstractThe barrier to CO oxidation on Pt catalysts is the strongly bound adsorbed CO, which inhibits O2 adsorption and hinders CO2 formation. Using reaction studies and in situ X-ray spectroscopy with colloidally prepared, monodisperse ∼2 nm Pt and PtSn nanoparticle catalysts, we show that the addition of Sn to Pt provides distinctly different reaction sites and a more efficient reaction mechanism for CO oxidation compared to pure Pt catalysts. To probe the influence of Sn, we intentionally poisoned the Pt component of the nanoparticle catalysts using a CO-rich atmosphere. With a reaction environment comprised of 100 Torr CO and 40 Torr O2 and a temperature range between 200 and 300 C, Pt and PtSn catalysts exhibited activation barriers for CO2 formation of 133 kJ/mol and 35 kJ/mol, respectively. While pure Sn is readily oxidized and is not active for CO oxidation, the addition of Sn to Pt provides an active site for O2 adsorption that is important when Pt is covered with CO. Sn oxide was identified as the active Sn species under reaction conditions by in situ ambient pressure X-ray photoelectron spectroscopy measurements. While chemical signatures of Pt and Sn indicated intermixed metallic components under reducing conditions, Pt and Sn were found to reversibly separate into isolated domains of Pt and oxidic Sn on the nanoparticle surface under reaction conditions of 100 mTorr CO and 40 mTorr O2 between temperatures of 200-275 C. Under these conditions, PtSn catalysts exhibited apparent reaction orders in O2 for CO 2 production that were 0.5 and lower with increasing partial pressures. These reaction orders contrast the first-order dependence in O 2 known for pure Pt. The differences in activation barriers, non-first-order dependence in O2, and the presence of a partially oxidized Sn indicate that the enhanced activity is due to a reaction mechanism that occurs at a Pt/Sn oxide interface present at the nanoparticle surface. © 2014 Published by Elsevier Inc.en
dc.description.sponsorshipThis research was funded by the U.S. Department of Energy, Office of Basic Energy Sciences, under contract no. DE-AC02-05CH11231. K.K. also acknowledges funding provided by the UCB-KAUST Academic Excellence Alliance (AEA) Program. This work was performed in part at the Molecular Foundry and the Advanced Light Source, beamline 9.3.2 of the Lawrence Berkeley National Laboratory. 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.en
dc.publisherElsevier BVen
dc.subjectAmbient pressure X-ray photoelectron spectroscopyen
dc.subjectCarbon monoxide oxidationen
dc.subjectCatalysisen
dc.subjectInterfaceen
dc.subjectNanoparticleen
dc.subjectPten
dc.subjectRedox coupleen
dc.subjectSnen
dc.titleCO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditionsen
dc.typeArticleen
dc.identifier.journalJournal of Catalysisen
dc.contributor.institutionLawrence Berkeley National Laboratory, Berkeley, United Statesen
dc.contributor.institutionUC Berkeley, Berkeley, United Statesen
kaust.grant.programAcademic Excellence Alliance (AEA)en
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