CO oxidation by Pd supported on CeO2(100) and CeO2(111) facets

Giulia Spezzati, Angelica D. Benavidez, Andrew T. DeLaRiva, Yaqiong Su, Jan P. Hofmann, Shunsuke Asahina, Ezra J. Olivier, Johannes H. Neethling, Jeffrey T. Miller, Abhaya K. Datye, Emiel J.M. Hensen

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Pd/CeO2 is an active component in emission control catalysts for CO oxidation. Nanostructured CeO2 powders can be prepared in the form of rods exposing predominantly (111) surfaces and cubes exposing (100) surfaces. While differences in the reactivity of Pd supported on these facets of ceria have been reported, the origins of the reactivity differences are not well understood. Pd supported on (111) surfaces of ceria rods exhibits room-temperature CO oxidation activity, while Pd on (100) surface of ceria cubes shows comparable activity at a temperature that is 60 °C higher. Earlier, we established that Pd/CeO2-rods are active due to a Langmuir-Hinshelwood mechanism involving isolated Pd atoms in the form of Pd1O and Pd1O2 species. Here, we establish using in situ CO IR spectroscopy and density functional theory (DFT) that, in addition to TEM-visible Pd nanoparticles, Pd/CeO2-cubes also contain isolated Pd species, predominantly in the form of Pd1O. DFT calculations show that CO oxidation proceeds via a Mars-van Krevelen pathway, which is possible for the (100) surface because of the lower Ce-O binding energy compared to the (111) surface. Overall, the catalytic cycle for CO oxidation on Pd/CeO2(100) involves a higher free energy barrier than on Pd/CeO2(111) in keeping with the experimentally observed activity difference. EXAFS measurements show that the active Pd phase in both Pd/CeO2-rods and Pd/CeO2-cubes responds dynamically with respect to reducing and oxidizing conditions. The redispersion of Pd in oxidative conditions is more pronounced for Pd/CeO2-rods and the catalyst is more active after an oxidative treatment.

LanguageEnglish
Pages36-46
Number of pages11
JournalApplied Catalysis. B, Environmental
Volume243
DOIs
StatePublished - Apr 2019

Fingerprint

Carbon Monoxide
oxidation
Oxidation
Cerium compounds
Density functional theory
catalyst
Catalysts
Energy barriers
Emission control
emission control
Binding energy
Powders
subspecies
Free energy
energy
transmission electron microscopy
Mars
Infrared spectroscopy
Thermodynamic properties
temperature

Keywords

  • CeO
  • CO oxidation
  • Palladium
  • Reaction mechanism
  • Single atoms

Cite this

Spezzati, Giulia ; Benavidez, Angelica D. ; DeLaRiva, Andrew T. ; Su, Yaqiong ; Hofmann, Jan P. ; Asahina, Shunsuke ; Olivier, Ezra J. ; Neethling, Johannes H. ; Miller, Jeffrey T. ; Datye, Abhaya K. ; Hensen, Emiel J.M./ CO oxidation by Pd supported on CeO2(100) and CeO2(111) facets. In: Applied Catalysis. B, Environmental. 2019 ; Vol. 243. pp. 36-46
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title = "CO oxidation by Pd supported on CeO2(100) and CeO2(111) facets",
abstract = "Pd/CeO2 is an active component in emission control catalysts for CO oxidation. Nanostructured CeO2 powders can be prepared in the form of rods exposing predominantly (111) surfaces and cubes exposing (100) surfaces. While differences in the reactivity of Pd supported on these facets of ceria have been reported, the origins of the reactivity differences are not well understood. Pd supported on (111) surfaces of ceria rods exhibits room-temperature CO oxidation activity, while Pd on (100) surface of ceria cubes shows comparable activity at a temperature that is 60 °C higher. Earlier, we established that Pd/CeO2-rods are active due to a Langmuir-Hinshelwood mechanism involving isolated Pd atoms in the form of Pd1O and Pd1O2 species. Here, we establish using in situ CO IR spectroscopy and density functional theory (DFT) that, in addition to TEM-visible Pd nanoparticles, Pd/CeO2-cubes also contain isolated Pd species, predominantly in the form of Pd1O. DFT calculations show that CO oxidation proceeds via a Mars-van Krevelen pathway, which is possible for the (100) surface because of the lower Ce-O binding energy compared to the (111) surface. Overall, the catalytic cycle for CO oxidation on Pd/CeO2(100) involves a higher free energy barrier than on Pd/CeO2(111) in keeping with the experimentally observed activity difference. EXAFS measurements show that the active Pd phase in both Pd/CeO2-rods and Pd/CeO2-cubes responds dynamically with respect to reducing and oxidizing conditions. The redispersion of Pd in oxidative conditions is more pronounced for Pd/CeO2-rods and the catalyst is more active after an oxidative treatment.",
keywords = "CeO, CO oxidation, Palladium, Reaction mechanism, Single atoms",
author = "Giulia Spezzati and Benavidez, {Angelica D.} and DeLaRiva, {Andrew T.} and Yaqiong Su and Hofmann, {Jan P.} and Shunsuke Asahina and Olivier, {Ezra J.} and Neethling, {Johannes H.} and Miller, {Jeffrey T.} and Datye, {Abhaya K.} and Hensen, {Emiel J.M.}",
year = "2019",
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Spezzati, G, Benavidez, AD, DeLaRiva, AT, Su, Y, Hofmann, JP, Asahina, S, Olivier, EJ, Neethling, JH, Miller, JT, Datye, AK & Hensen, EJM 2019, 'CO oxidation by Pd supported on CeO2(100) and CeO2(111) facets' Applied Catalysis. B, Environmental, vol. 243, pp. 36-46. DOI: 10.1016/j.apcatb.2018.10.015

CO oxidation by Pd supported on CeO2(100) and CeO2(111) facets. / Spezzati, Giulia; Benavidez, Angelica D.; DeLaRiva, Andrew T.; Su, Yaqiong; Hofmann, Jan P.; Asahina, Shunsuke; Olivier, Ezra J.; Neethling, Johannes H.; Miller, Jeffrey T.; Datye, Abhaya K.; Hensen, Emiel J.M.

In: Applied Catalysis. B, Environmental, Vol. 243, 04.2019, p. 36-46.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - CO oxidation by Pd supported on CeO2(100) and CeO2(111) facets

AU - Spezzati,Giulia

AU - Benavidez,Angelica D.

AU - DeLaRiva,Andrew T.

AU - Su,Yaqiong

AU - Hofmann,Jan P.

AU - Asahina,Shunsuke

AU - Olivier,Ezra J.

AU - Neethling,Johannes H.

AU - Miller,Jeffrey T.

AU - Datye,Abhaya K.

AU - Hensen,Emiel J.M.

PY - 2019/4

Y1 - 2019/4

N2 - Pd/CeO2 is an active component in emission control catalysts for CO oxidation. Nanostructured CeO2 powders can be prepared in the form of rods exposing predominantly (111) surfaces and cubes exposing (100) surfaces. While differences in the reactivity of Pd supported on these facets of ceria have been reported, the origins of the reactivity differences are not well understood. Pd supported on (111) surfaces of ceria rods exhibits room-temperature CO oxidation activity, while Pd on (100) surface of ceria cubes shows comparable activity at a temperature that is 60 °C higher. Earlier, we established that Pd/CeO2-rods are active due to a Langmuir-Hinshelwood mechanism involving isolated Pd atoms in the form of Pd1O and Pd1O2 species. Here, we establish using in situ CO IR spectroscopy and density functional theory (DFT) that, in addition to TEM-visible Pd nanoparticles, Pd/CeO2-cubes also contain isolated Pd species, predominantly in the form of Pd1O. DFT calculations show that CO oxidation proceeds via a Mars-van Krevelen pathway, which is possible for the (100) surface because of the lower Ce-O binding energy compared to the (111) surface. Overall, the catalytic cycle for CO oxidation on Pd/CeO2(100) involves a higher free energy barrier than on Pd/CeO2(111) in keeping with the experimentally observed activity difference. EXAFS measurements show that the active Pd phase in both Pd/CeO2-rods and Pd/CeO2-cubes responds dynamically with respect to reducing and oxidizing conditions. The redispersion of Pd in oxidative conditions is more pronounced for Pd/CeO2-rods and the catalyst is more active after an oxidative treatment.

AB - Pd/CeO2 is an active component in emission control catalysts for CO oxidation. Nanostructured CeO2 powders can be prepared in the form of rods exposing predominantly (111) surfaces and cubes exposing (100) surfaces. While differences in the reactivity of Pd supported on these facets of ceria have been reported, the origins of the reactivity differences are not well understood. Pd supported on (111) surfaces of ceria rods exhibits room-temperature CO oxidation activity, while Pd on (100) surface of ceria cubes shows comparable activity at a temperature that is 60 °C higher. Earlier, we established that Pd/CeO2-rods are active due to a Langmuir-Hinshelwood mechanism involving isolated Pd atoms in the form of Pd1O and Pd1O2 species. Here, we establish using in situ CO IR spectroscopy and density functional theory (DFT) that, in addition to TEM-visible Pd nanoparticles, Pd/CeO2-cubes also contain isolated Pd species, predominantly in the form of Pd1O. DFT calculations show that CO oxidation proceeds via a Mars-van Krevelen pathway, which is possible for the (100) surface because of the lower Ce-O binding energy compared to the (111) surface. Overall, the catalytic cycle for CO oxidation on Pd/CeO2(100) involves a higher free energy barrier than on Pd/CeO2(111) in keeping with the experimentally observed activity difference. EXAFS measurements show that the active Pd phase in both Pd/CeO2-rods and Pd/CeO2-cubes responds dynamically with respect to reducing and oxidizing conditions. The redispersion of Pd in oxidative conditions is more pronounced for Pd/CeO2-rods and the catalyst is more active after an oxidative treatment.

KW - CeO

KW - CO oxidation

KW - Palladium

KW - Reaction mechanism

KW - Single atoms

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