Segregation dynamics of a Pd-Ag surface during CO oxidation investigated by NAP-XPS

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Segregation dynamics of a Pd-Ag surface during CO oxidation investigated by NAP-XPS

Strømsheim, Marie D. (author): Norwegian University of Science and Technology

Svenum, Ingeborg Helene (author): Foundation for Scientific and Industrial Research (SINTEF),Norwegian University of Science and Technology

Mahmoodinia, Mehdi (author): Norwegian University of Science and Technology

Boix, Virgínia (author): Lund University,Lunds universitet,Synkrotronljusfysik,Fysiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Synchrotron Radiation Research,Department of Physics,Departments at LTH,Faculty of Engineering, LTH

Knudsen, Jan (author): Lund University,Lunds universitet,NanoLund: Centre for Nanoscience,Annan verksamhet, LTH,Lunds Tekniska Högskola,MAX IV-laboratoriet,Synkrotronljusfysik,Fysiska institutionen,Institutioner vid LTH,Other operations, LTH,Faculty of Engineering, LTH,MAX IV Laboratory,Synchrotron Radiation Research,Department of Physics,Departments at LTH,Faculty of Engineering, LTH

Venvik, Hilde J. (author): Norwegian University of Science and Technology

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Elsevier BV, 2022
2022
English.
In: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 384-386, s. 265-273

Related links:: http://dx.doi.org/10... (free); show more...; https://doi.org/10.1...; https://lup.lub.lu.s...; https://doi.org/10.1...; show less...

Journal article (peer-reviewed)

Abstract Subject headings

The dynamic changes in composition in the near-surface region of a Pd75%Ag25%(100) single crystal were monitored using near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) during CO oxidation under oxygen rich conditions at a total pressure of 1.1 mbar. Six CO oxidation temperature cycles were investigated at different heating rates and maximum temperatures of 450 °C or 600 °C. It was found that the history of the bimetallic sample plays an important role, as the CO2 formation profile varies depending on initial conditions, and previous heating rates and maximum temperatures. In terms of CO coverage effects, normal, reversed and no hysteresis behaviour were all observed. In agreement with previous modelling predictions, the NAP-XPS data confirm a dynamic segregation behaviour upon heating/cooling where the amount of Pd in the surface region decreases with increasing temperature. Nevertheless, the Pd 3d5/2 core level relative area assessment is not fully capable of capturing all the surface dynamics inferred from the temperature dependent CO2 formation profiles, due to the probing depth. While residing at ambient temperature in the reaction mixture, however, there is a build-up of adsorbed CO at the surface showing that CO induces segregation of Pd to the topmost surface layer under these conditions. In total, this suggests that the segregation is kinetically relatively facile during temperature cycling, and that adsorbate coverage is the main controlling factor for the surface termination.

Subject headings

TEKNIK OCH TEKNOLOGIER -- Kemiteknik -- Kemiska processer (hsv//swe)
ENGINEERING AND TECHNOLOGY -- Chemical Engineering -- Chemical Process Engineering (hsv//eng)
NATURVETENSKAP -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)
NATURAL SCIENCES -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)
NATURVETENSKAP -- Fysik -- Den kondenserade materiens fysik (hsv//swe)
NATURAL SCIENCES -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Keyword

Bimetallic catalysis
Carbon monoxide oxidation
Palladium
Segregation
Silver
Single crystal surface

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By the author/editor: Strømsheim, Mari ...; Svenum, Ingeborg ...; Mahmoodinia, Meh ...; Boix, Virgínia; Knudsen, Jan; Venvik, Hilde J.

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ENGINEERING AND TECHNOLOGY: ENGINEERING AND ...; and Chemical Enginee ...; and Chemical Process ...

NATURAL SCIENCES: NATURAL SCIENCES; and Biological Scien ...; and Biochemistry and ...

NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Condensed Matter ...

Articles in the publication: Catalysis Today

By the university: Lund University

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