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Detecting and utilizing minority phases in heterogeneous catalysis

View Article: PubMed Central - PubMed

ABSTRACT

Highly active phases in carbon monoxide oxidation are known, however they are transient in nature. Here, we determined for the first time the structure of such a highly active phase on platinum nanoparticles in an actual reactor. Unlike generally assumed, the surface of this phase is virtually free of adsorbates and co-exists with carbon-monoxide covered and surface oxidized platinum. Understanding the relation between gas composition and catalyst structure at all times and locations within a reactor enabled the rational design of a reactor concept, which maximizes the amount of the highly active phase and minimizes the amount of platinum needed.

No MeSH data available.


(A) Measured and (B) simulated mass spectrometry traces of carbon monoxide, oxygen, and carbon dioxide during the switch from a carbon monoxide atmosphere to a CO/O2 atmosphere. Measured and simulated data have identical features, including a pronounced peak in the oxygen signal before the increase to equilibrium level, caused by the lower activity of the initially present carbon monoxide-poisoned nanoparticles. There also is an overshoot in the carbon dioxide signal at the moment of light off, originating from the reaction of the chemisorbed carbon monoxide on the platinum nanoparticles, as observed earlier in oscillatory kinetics11.
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f2: (A) Measured and (B) simulated mass spectrometry traces of carbon monoxide, oxygen, and carbon dioxide during the switch from a carbon monoxide atmosphere to a CO/O2 atmosphere. Measured and simulated data have identical features, including a pronounced peak in the oxygen signal before the increase to equilibrium level, caused by the lower activity of the initially present carbon monoxide-poisoned nanoparticles. There also is an overshoot in the carbon dioxide signal at the moment of light off, originating from the reaction of the chemisorbed carbon monoxide on the platinum nanoparticles, as observed earlier in oscillatory kinetics11.

Mentions: Figure 2A depicts the composition of the reactor exhaust as determined by mass spectrometry during the switch. The most notable features are: the carbon dioxide signal increases and the oxygen signal goes through a maximum. The carbon dioxide signal reaches a maximum just before stabilizing at equilibrium. These features in the exhaust gas composition are clearly reproduced by the reactor simulation, which is based solely on the kinetic model that describes the experimentally determined structures using the XAS data (Fig. 2B). Because the mass spectrometry data and the structural characterization are simultaneously performed, they can be quantitatively correlated.


Detecting and utilizing minority phases in heterogeneous catalysis
(A) Measured and (B) simulated mass spectrometry traces of carbon monoxide, oxygen, and carbon dioxide during the switch from a carbon monoxide atmosphere to a CO/O2 atmosphere. Measured and simulated data have identical features, including a pronounced peak in the oxygen signal before the increase to equilibrium level, caused by the lower activity of the initially present carbon monoxide-poisoned nanoparticles. There also is an overshoot in the carbon dioxide signal at the moment of light off, originating from the reaction of the chemisorbed carbon monoxide on the platinum nanoparticles, as observed earlier in oscillatory kinetics11.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121607&req=5

f2: (A) Measured and (B) simulated mass spectrometry traces of carbon monoxide, oxygen, and carbon dioxide during the switch from a carbon monoxide atmosphere to a CO/O2 atmosphere. Measured and simulated data have identical features, including a pronounced peak in the oxygen signal before the increase to equilibrium level, caused by the lower activity of the initially present carbon monoxide-poisoned nanoparticles. There also is an overshoot in the carbon dioxide signal at the moment of light off, originating from the reaction of the chemisorbed carbon monoxide on the platinum nanoparticles, as observed earlier in oscillatory kinetics11.
Mentions: Figure 2A depicts the composition of the reactor exhaust as determined by mass spectrometry during the switch. The most notable features are: the carbon dioxide signal increases and the oxygen signal goes through a maximum. The carbon dioxide signal reaches a maximum just before stabilizing at equilibrium. These features in the exhaust gas composition are clearly reproduced by the reactor simulation, which is based solely on the kinetic model that describes the experimentally determined structures using the XAS data (Fig. 2B). Because the mass spectrometry data and the structural characterization are simultaneously performed, they can be quantitatively correlated.

View Article: PubMed Central - PubMed

ABSTRACT

Highly active phases in carbon monoxide oxidation are known, however they are transient in nature. Here, we determined for the first time the structure of such a highly active phase on platinum nanoparticles in an actual reactor. Unlike generally assumed, the surface of this phase is virtually free of adsorbates and co-exists with carbon-monoxide covered and surface oxidized platinum. Understanding the relation between gas composition and catalyst structure at all times and locations within a reactor enabled the rational design of a reactor concept, which maximizes the amount of the highly active phase and minimizes the amount of platinum needed.

No MeSH data available.