Abstract
Developing better three-way catalysts with improved low-temperature performance is essential for cold start emission control. Density functional theory in combination with microkinetics simulations is used to predict reactivity of CO/NO/H(2) mixtures on a small Pd cluster on CeO(2)(111). At low temperatures, N(2)O formation occurs via a N(2)O(2) dimer over metallic Pd(3). Part of the N(2)O intermediate product re-oxidizes Pd, limiting NO conversion and requiring rich conditions to obtain high N(2) selectivity. High N(2) selectivity at elevated temperatures is due to N(2)O decomposition on oxygen vacancies. Doping CeO(2) by Fe is predicted to lead to more oxygen vacancies and a higher N(2) selectivity, which is validated by the lower onset of N(2) formation for a Pd catalyst supported on Fe-doped CeO(2) prepared by flame spray pyrolysis. Activating ceria surface oxygen by transition metal doping is a promising strategy to improve the performance of three-way catalysts.