First principles investigation of NO2 and SO2 adsorption on γ-Al2O3 supported mono- and diatomic metal clusters

Abstract

NO_x storage/reduction catalysts have been developed in the 1990's to minimize the emission of harmful NO and NO₂ gases as a result of lean burning in diesel engines. Sulfur poisoning of the catalyst occurs when SO_x (x = 2–3) species present in the fuel react aggressively with both the storage and the precious metal redox components. In the present work, DFT calculations within the plane wave, pseudopotential GGA framework were performed to study NO₂ and SO₂ adsorption on mono and diatomic clusters of Pt and Rh supported on the γ-Al₂O₃ (100) surface. The most stable adsorption geometries for the clusters on the surface were identified and used as anchoring points for the adsorption of NO₂ and SO₂ molecules. Binding energies of a large number of NO₂ and SO₂ adsorption geometries were reported. In all cases where direct comparison between NO₂ and SO₂ binding geometries was possible, NO₂ binding energies were observed to be larger than SO₂ binding energies, in some cases by more than 1 eV.