The dynamic surface chemistry during the interaction of CO with ceria captured by Raman spectroscopy |
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Authors: | Meghan Swanson Vladimir V Pushkarev Vladimir I Kovalchuk Julie L d’Itri |
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Affiliation: | (1) Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA |
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Abstract: | The interaction of CO with ceria under conditions typically used to measure the oxygen storage capacity (OSC) of automotive
three way catalysts (TWC) has been investigated by in situ Raman spectroscopy. During exposure of the ceria to CO at 623 K vibrational bands at 1582–1600 and 1331–1340 cm−1 appeared; these bands increased with increasing time of exposure to CO. The band positions are consistent with phonon modes
of carbon; however, assignment to carboxylate species or carbonate species cannot be excluded. Subsequent exposure to O2 at room temperature resulted in a decrease in the intensities of the 1582–1600 and 1331–1340 cm−1 bands by more than 90%. As well, exposure to O2 at room temperature also resulted in the appearance of Raman modes characteristic of formate and peroxide surface species.
The mechanism by which formate forms upon room temperature O2 exposure is discussed in the context of the assignment of the 1582–1600 and 1331–1340 cm−1 bands to carbon phonon modes which result from the disproportionation of CO on reduced ceria. |
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Keywords: | CO adsorption ceria CO disproportionation carbonates carboxylates oxygen storage capacity in situ Raman spectroscopy |
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