Electron-induced surface chemistry: Production and characterization of NH2 and NH species on Pt(111)

Abstract

A lowenergy electron diffraction data acquisition system for very low electron doses based upon a slow scan charge coupled device camera Rev.Irradiating molecularly adsorbed NH 3 with controlled fluences of 50 eV electrons on Pt͑111͒ at 100 K leads to NH 2 , NH, and H species. Temperature programmed desorption shows dihydrogen desorption, confirming electron induced decomposition of ammonia, and a new NH 3 desorption peak ͑210 K͒ attributed to hydrogenation of NH 2 . High resolution electron energy loss spectroscopy identifies NH 2 through two vibrational features at 830 and 1392 cm Ϫ1 that are assigned to rocking and wagging modes, and NH through a single strong stretching feature at 3280 cm Ϫ1 . NH was stable up to 400 K where it dehydrogenated, leaving N on the surface, which was stable up to 700 K. In x-ray photoelectron spectroscopy a N(1s) peak, shifted to lower binding energy, appears after electron irradiation.

Catalytic decomposition of ammonia over silicon-carbide nanotube: a DFT study

“…N ? H. This is significantly larger than the corresponding barriers on Pt(111) (32 kcal/mol) and Pt(100) (24 kcal/mol) [48]. In light of the relatively high reaction barrier and the endothermicity of this reaction, it is thus expected that the dissociation of NH fragment on SiCNT is unfavorable both kinetically and thermodynamically, which is consistent with the other theoretical results [36][37][38].…”

“…All of these NH x species have been experimentally observed on metal surface using surface sensitive techniques such as high resolution electron energy loss spectroscopy (HREELS) [48,49]. A recent study [36] suggests that the successive dehydrogenation of ammonia over Fe(100) surface is not a quick kinetic process, but rather sizeable activation energy barriers exist along the reaction pathway.…”

Low-temperature ammonia oxidation on platinum sponge studied with positron emission profiling

“…According to Sun et al [34], the peak at lower binding energy of 398.0 eV is assigned to NH and the peak at higher binding energy to NH 2 species. The BE peaks representing NO (a) [35,36], NH 3 [34,37], N 2 [38], N 2 O [39], and atomic nitrogen [40] were not observed in our XP spectra.…”

The catalytic reduction of NO by H2 on Ru(0001): Observation of NHads species

“…Unfortunately, not much XPS data on NH x fragments with clear assignment of the peak positions were available in the literature (Table 2). Sun et al [31] and Weststrate et al [32] reported the BE of 397.5 eV and 397.6 eV for the NH ads species on the Pt(1 1 1) and Ir(1 1 0) surfaces, respectively. Assuming the correctness of the above outlined BE assignments, we suggested that the NH ads species was present on the Ru(0 0 0 1) surface during the steadystate catalytic reduction of nitric oxide with excess hydrogen.…”

“…The rule of thumb is that the DBE between different NH x,ads species is approximately 1 eV (see for instance Refs. [31,32] and Table 2). From this point of view, the DBE between NH ads (397.4 eV) and N ads (397.1 eV), which is only 0.3 eV, does not look very convincing.…”