Reversed Hysteresis during CO Oxidation over Pd75Ag25(100)
Artikel i vetenskaplig tidskrift, 2016

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.

ray photoelectron-spectroscopy

surface

microkinetic modeling

density-functional calculations

carbon-monoxide oxidation

bimetallic catalysts

pressure conditions

pd(111) surfaces

NAP-XPS

segregation

Pd(100)

ultrahigh-vacuum

pt-group metals

hydrogen

hysteresis

Chemistry

Pd75Ag25(100)

ambient

DFT

CO oxidation

adsorption

Författare

V. R. Fernandes

Norges teknisk-naturvitenskapelige universitet

Maxime van den Bossche

Kompetenscentrum katalys (KCK)

Chalmers, Fysik, Kemisk fysik

J. Knudsen

Lunds universitet

M. H. Farstad

Norges teknisk-naturvitenskapelige universitet

J. Gustafson

Lunds universitet

H. J. Venvik

Norges teknisk-naturvitenskapelige universitet

Henrik Grönbeck

Chalmers, Fysik, Kemisk fysik

Kompetenscentrum katalys (KCK)

A. Borg

Norges teknisk-naturvitenskapelige universitet

ACS Catalysis

2155-5435 (eISSN)

Vol. 6 7 4154-4161

Ämneskategorier

Fysikalisk kemi

DOI

10.1021/acscatal.6b00658

Mer information

Senast uppdaterat

2018-04-20