Importance of Pd and Pt excited states in N2O capture and activation: A comparative study with Rh and Au atoms

Abstract

Nitrous oxide (N2O) is an intermediate compound formed during catalysis occurring in automobile exhaust pipes. In this work, the N2O capture and activation by Pt and Pd atoms in the ground and excited states of many multiplicities are studied. Pt and Pd + N2O reactions are studied at multireference second-order perturbation level of theory using Cs symmetry. The PtN2O (1A′, 5A′, and 5A″) species are spontaneously created from excited states. Only the 5A′ and 5A″ states exhibit N2O activation reaction paths when N2O approaches Pt end-on by the N or O atoms side or side-on yielding NO or N2 as products, respectively. Pt+ cations ground and excited states, capture N2O, although only Pt+ (6A′ and 6A″) states show N2O activation yielding O and N2 as products. In the Pd atom case, PdN2O (1A′ and 5A″) species are also spontaneously created from excited states. The 5A″ state exhibits N2O activation yielding N2 + O as products. Pd+ cations in both ground and excited states capture N2O; however, only the [PdN2O]+ (4A′, 4A″, 6A′, and 6A″) states in side-on approaches and (6A′) in end-on approach activate the N2O and yield the N2 bounded to the metal and O as product. The results obtained in this work are discussed and compared with previous calculations of Rh and Au atoms. The reaction paths show a metal–gas dative covalent bonding character. Löwdin charge population analyses for Pt and Pd active states show a binding done through charge donation and retrodonation between the metals and N2O. © 2013 Wiley Periodicals, Inc.