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Activity Trends for Catalytic CO and NO Co-Oxidation at Low Temperature Diesel Emission Conditions

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journal contribution
posted on 28.08.2018, 00:00 by Yuying Song, Lars C. Grabow
The diesel oxidation catalyst (DOC) is an essential component of modern vehicle emissions control systems. The pervasive challenge for low temperature oxidation of engine exhaust gas is the mutual inhibition between the various pollutants, causing a marked increase in light-off temperature. Using a combination of density functional theory and descriptor-based microkinetic modeling, we have screened catalysts for low temperature co-oxidation of CO and NO with specific emphasis on minimizing inhibition effects. Compared to standard Pt–Pd alloys, we find that coinage metal alloys, i.e., Cu, Ag, and Au with at least one oxophilic constituent, should possess more robust low temperature activity with minimal inhibition. We attribute this remarkable performance to high surface concentrations of oxygen due to the oxophilic component and less competitive adsorption between CO and NO to the exposed coinage metal sites. We believe that these fundamental insights provide valuable design principles for improved low temperature oxidation catalysts.

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