Mechanism of N2O Formation During NO Reduction on the Au(111) Surface

Abstract

Density functional theory calculations have been performed to elucidate the mechanism of N2O formation over the Au(111) surface during NO reduction. It is shown that the dissociation of NO into an N atom and an O atom involves a barrier as high as 3.9 eV, implying that the formation of N2O does not occur via the direct dissociation mechanism of NO. Alternatively, we find that the reaction may occur via a dimer mechanism; i.e., two NO molecules initially associate into a dimeric (NO)2, which then dissociates into a N2O molecule and a N atom. We have scanned the potential energy surface forming N2O along different pathways, which involve a trapezoid OadNNOad dimer, an inverted trapezoid ONadNadO dimer, a zigzag ONadNOad dimer, or a rhombus ONadOadN dimer. The trapezoid dimer, OadNNOad, is found to be a necessary intermediate for the formation of N2O, and the calculated barrier for the rate-determining step along the energetically most favorable pathway is only 0.34 eV. The present results rationalize the ea...