Improved Pd/CeO2 Catalysts for Low-Temperature NO Reduction: Activation of CeO2 Lattice Oxygen by Fe Doping

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 CeO2(111). At low temperatures, N2O formation occurs via a N2O2 dimer over metallic Pd-3. Part of the N2O 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 N2O decomposition on oxygen vacancies. Doping CeO2 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 CeO2 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.

Automated summary

Developing better three-way catalysts with improved low-temperature performance is crucial for cold start emission control. Research shows that N2O formation can be reduced and N-2 selectivity can be improved at low temperatures by combining metal Pd and CeO2 in reactions; it is predicted that doping CeO2 with Fe can increase oxygen vacancies and lower the onset temperature of N-2 formation for a Pd catalyst supported on Fe-doped CeO2 prepared by flame spray pyrolysis.