Unravelling the Different Reaction Pathways for Low Temperature CO Oxidation on Pt/CeO₂ and Pt/Al₂O₃ by Spatially Resolved Structure–Activity Correlations

Abstract

Spatially resolved <i>operando</i> HERFD-XANES (high energy resolution fluorescence detected X-ray absorption near edge structure) complemented by CO concentration gradient profiles along the catalyst bed (SpaciPro) was used to identify the dominant reaction paths for the low and high temperature CO oxidation on Pt/CeO₂ and Pt/Al₂O₃. At low temperatures, features associated with CO adsorption on Pt were found for both catalysts. During the oxidation reaction light-off, the evolution of the spectral and catalytic profile diverged along the catalyst bed. The CO oxidation rate was high on Pt/CeO₂ from the beginning of the catalyst bed with CO being adsorbed on Pt, whereas low CO conversion due to strong CO poisoning was found on Pt/Al₂O₃. This correlation of the CO concentration gradient with unique insight by HERFD-XANES gave direct proof of the crucial contribution of the Pt-CeO₂ perimeter sites overcoming the CO self-inhibition effect at low temperatures.