Advanced

Reversed Hysteresis during CO Oxidation over Pd75Ag25(100)

Fernandes, Vasco R.; Bossche, Maxime Van Den; Knudsen, Jan LU ; Farstad, Mari H.; Gustafson, Johan LU ; Venvik, Hilde J.; Grönbeck, Henrik and Borg, Anne (2016) In ACS Catalysis 6(7). p.4154-4161
Abstract

CO oxidation over Pd(100) and Pd75Ag25(100) has been investigated by a combination of near-ambient-pressure X-ray photoelectron spectroscopy, quadrupole mass spectrometry, density functional theory calculations, and microkinetic modeling. For both surfaces, hysteresis is observed in the CO2 formation during the heating and cooling cycles. Whereas normal hysteresis with light-off temperature higher than extinction temperature is present for Pd(100), reversed hysteresis is observed for Pd75Ag25(100). The reversed hysteresis can be explained by dynamic changes in the surface composition. At the beginning of the heating ramp, the surface is rich in palladium, which gives a CO coverage... (More)

CO oxidation over Pd(100) and Pd75Ag25(100) has been investigated by a combination of near-ambient-pressure X-ray photoelectron spectroscopy, quadrupole mass spectrometry, density functional theory calculations, and microkinetic modeling. For both surfaces, hysteresis is observed in the CO2 formation during the heating and cooling cycles. Whereas normal hysteresis with light-off temperature higher than extinction temperature is present for Pd(100), reversed hysteresis is observed for Pd75Ag25(100). The reversed hysteresis can be explained by dynamic changes in the surface composition. At the beginning of the heating ramp, the surface is rich in palladium, which gives a CO coverage that poisons the surface until the desorption rate becomes sufficiently high. The thermodynamic preference for an Ag-rich surface in the absence of adsorbates promotes diffusion of Ag from the bulk to the surface as CO desorbs. During the cooling ramp, an appreciable surface coverage is reached at temperatures too low for efficient diffusion of Ag back into the bulk. The high concentration of Ag in the surface leads to a high extinction temperature and, consequently, the reversed hysteresis.

(Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
CO oxidation, DFT, hysteresis, microkinetic modeling, NAP-XPS, Pd(100), PdAg(100)
in
ACS Catalysis
volume
6
issue
7
pages
8 pages
publisher
The American Chemical Society
external identifiers
  • scopus:84977080444
  • wos:000379457300013
ISSN
2155-5435
DOI
10.1021/acscatal.6b00658
language
English
LU publication?
yes
id
265ee443-dba2-4e56-8f10-8360eb388d4e
date added to LUP
2017-01-17 16:24:07
date last changed
2017-11-19 04:36:47
@article{265ee443-dba2-4e56-8f10-8360eb388d4e,
  abstract     = {<p>CO oxidation over Pd(100) and Pd<sub>75</sub>Ag<sub>25</sub>(100) has been investigated by a combination of near-ambient-pressure X-ray photoelectron spectroscopy, quadrupole mass spectrometry, density functional theory calculations, and microkinetic modeling. For both surfaces, hysteresis is observed in the CO<sub>2</sub> formation during the heating and cooling cycles. Whereas normal hysteresis with light-off temperature higher than extinction temperature is present for Pd(100), reversed hysteresis is observed for Pd<sub>75</sub>Ag<sub>25</sub>(100). The reversed hysteresis can be explained by dynamic changes in the surface composition. At the beginning of the heating ramp, the surface is rich in palladium, which gives a CO coverage that poisons the surface until the desorption rate becomes sufficiently high. The thermodynamic preference for an Ag-rich surface in the absence of adsorbates promotes diffusion of Ag from the bulk to the surface as CO desorbs. During the cooling ramp, an appreciable surface coverage is reached at temperatures too low for efficient diffusion of Ag back into the bulk. The high concentration of Ag in the surface leads to a high extinction temperature and, consequently, the reversed hysteresis.</p>},
  author       = {Fernandes, Vasco R. and Bossche, Maxime Van Den and Knudsen, Jan and Farstad, Mari H. and Gustafson, Johan and Venvik, Hilde J. and Grönbeck, Henrik and Borg, Anne},
  issn         = {2155-5435},
  keyword      = {CO oxidation,DFT,hysteresis,microkinetic modeling,NAP-XPS,Pd(100),PdAg(100)},
  language     = {eng},
  month        = {07},
  number       = {7},
  pages        = {4154--4161},
  publisher    = {The American Chemical Society},
  series       = {ACS Catalysis},
  title        = {Reversed Hysteresis during CO Oxidation over Pd<sub>75</sub>Ag<sub>25</sub>(100)},
  url          = {http://dx.doi.org/10.1021/acscatal.6b00658},
  volume       = {6},
  year         = {2016},
}