N2 emission in NO and N2O reduction on Rh(100) and Rh(110)

Abstract

The angular distribution of desorbing N(2) was studied in both the thermal decomposition of N(2)O(a) on Rh(100) at 60-140 K and the steady-state NO (or N(2)O) + D(2) reaction on Rh(100) and Rh(110) at 280-900 K. In the former, N(2) desorption shows two peaks at around 85 and 110 K. At low N(2)O coverage, the desorption at 85 K collimates at about 66 degrees off normal towards the [001] direction, whereas at high coverage, it sharply collimates along the surface normal. In the NO reduction on Rh(100), the N(2) desorption preferentially collimates at around 71 degrees off normal towards the [001] direction below about 700 K, whereas it collimates predominantly along the surface normal at higher temperatures. At lower temperatures, the surface nitrogen removal in the NO reduction is due to the process of NO(a) + N(a) --> N(2)O(a) --> N(2)(g) + O(a). On the other hand, in the steady-state N(2)O + D(2) reaction on Rh(110), the N(2) desorption collimates closely along the [001] direction (close to the surface parallel) below 340 K and shifts to ca. 65 degrees off normal at higher temperatures. In the reduction with CO, the N(2) desorption collimates along around 65 degrees off normal towards the [001] direction above 520 K, and shifts to 45 degrees at 445 K with decreasing surface temperature. It is proposed that N(2)O is oriented along the [001] direction on both surfaces before dissociation and the emitted N(2) is not scattered by adsorbed hydrogen.

Surface reaction dynamics and energy partitioning

“…Nearly surface-parallel N 2 emission can be observed on Rh(110) at around 300 K when deposited oxygen is removed by hydrogen [84]. The N 2 emission is collimated at around 80° off normal.…”

Surface species studied by angle-resolved product desorption: Emission mechanism and spatial distribution

“…The surface-parallel N 2 emission can be observed on Rh(110) at around 300 K when deposited oxygen is removed by hydrogen [53]. The N 2 emission is collimated at around 80° off normal, which is almost a limiting value estimated from the van der Waals' radius of N 2 [59].…”

“…In the experiments, the fraction of N 2 signal due to the cosine distribution is enhanced at high CO pressures. The split angular distribution suggests the presence of at least two desorption components with different collimation angles [53,59]. Adsorbed CO suppresses the component that is closely surface-parallel.…”

“…This reduction is stable on Pd(110) in a wide temperature range (Fig. 7) [52], whereas it is highly retarded on Rh(110) when the N 2 O pressure is higher than that of CO or H 2 [53]. Using the new polar angle system in Fig.…”

Rhodium Nanoparticle Shape Dependence in the Reduction of NO by CO

“…The products of the reaction are CO 2 at all temperatures, N 2 O primarily (*75%) at the lower (\320°C) temperatures investigated in this study, and N 2 primarily at higher temperatures ([320°C) [12]. Although many mechanisms have been proposed for this reaction [14][15][16][17][18][19][20], it remains an open area of investigation [21,22] due to its enormous complexity. One relatively simple model, proposed by Permana et al [23], is as follows, where S refers to an available surface site:…”