Very Low Temperature Surface Reaction: N2O Formation from NO Dimers at 70 to 90 K on Ag{111}

Abstract

When Ag{ 11 l} is exposed to NO at 40 K, monolayer adsorption is followed by multilayer (N0)z formation. Heating to 60 K results in the desorption of the dimer multilayer, leaving a monolayer on the surface. Using isotopes, the monolayer has also been characterized as dimers, which have the N-N axis coplanar with the surface. At 70 to 90 K, N20 is formed from (N0)2 on the Ag{ 11 11 surface. Further heating to 120 K results in the desorption of the NzO. The reactive species is thus shown to be the adsorbed dimer, which cannot be formed at higher temperatures on exposure to NO because the surface coverage is too low. The monomer, adsorbed NO, is thus weakly adsorbed, in agreement with expectation.

Understanding the Role of Hyponitrite in Nitric Oxide Reduction

“…In this pathway, NO reduction proceeds via a "hyponitrite-like" (NO) 2 dimer (Scheme 1b), 20,22,[32][33][34] and, in fact, this intermediate has been detected directly with IR spectroscopy on Ag(111) at low temperatures (70 K). 22,35 (NO) 2 dimers have also been imaged on Cu(110) using scanning tunneling microscopy (STM), 33 and more recently, evidence for the formation (NO) 3 trimers on Cu(111) at 6 K has been collected with STM. 36 Nitric oxide also forms dimers on Pd(111) under certain conditions, as revealed by in situ infrared reflection absorption spectroscopy (IRAS).…”

Site-Selective Surface Reactions: Nitric Oxide Reduction on Mo(110)

“…Infrared spectroscopy was used to identify NO dimers on Ag(111) at temperatures as high as 90 K, and NÀN bond formation to evolve gaseous N 2 O was observed from these dimer precursors. [24,25] The same type of NO dimers on Cu(111) were subsequently observed using infrared spectroscopy. [26] The fact that the condensed-phase type dimers observed on these surfaces have n(NO) vibrational frequencies virtually unperturbed from those of true condensed-phase dimers suggests that their interaction with silver and copper is minimal.…”

Reaction of NO on Vanadium Oxide Surfaces: Observation of the NO Dimer Formation

“…3 However, formation of N2O on Ag(111) was observed when NO was adsorbed on the surface as low as 80 K. 4 In the case of the NO reaction on MgO, Rodriguez and co-workers suggested that the defective MgO surface was responsible for the production of N2O from NO, 5 while Kim and co-workers reported that more N2O was formed on a "low-defect" MgO surface below 75 K. 6 The anomaly in NO reactivity to form N2O at low temperatures on less-reactive surfaces can be explained by formation of (NO)2. [7][8][9] If the interaction of NO and the surface is week, NO molecules form dimeric NO on the surface. Thermal reaction of (NO)2 produces N2O.…”