XPS study of the adsorption of NH3 on nickel oxide on Ni(111)

Abstract

The aim of the present work was to investigate the initial stages of NH 3 interaction with nickel oxide layers formed on well-defined Ni(111) surfaces. The selected technique was x-ray photoelectron spectroscopy. Ammonia adsorption was performed at 10 −7 mbar and room temperature in a preparation chamber attached to the analysis chamber. After each adsorption, the N 1s core level was analysed and its intensity was plotted as a function of exposure (at the same pressure) to obtain the adsorption kinetics. The XPS peak shapes and the chemical shifts were related to the nature of the adsorption products. In our experimental conditions, we observed that the more reactive initial surface was the one covered by the O-adsorbed phase corresponding to the precursor state of the NiO formation. The NiO alone does not exhibit significant reactivity, whereas a mixture of NiO and the O-adsorbed phase shows a similar behaviour to that of the pure O-adsorbed phase. From the first adsorption until the last one, two nitrogen adspecies were detected: one with an N 1s binding energy (BE) of 397.8 eV and the other at 399.7 eV. The data indicate that the surface reactivity is structure-sensitive for the NiO layer and the mechanisms of adsorption seem to involve NH 3 dissociation into NH x adspecies, along with OH formation.

Ternary Transition Metal Oxide Nanoparticles with Spinel Structure for the Oxygen Reduction Reaction

“…26, 27 The lower intensity of the 2p satellite peaks and the asymmetrical shape of 2p3/2 indicate the mixed chemical environment of the Ni 2+ ions, which is present in both the octahedral and tetrahedral sites of the spinel lattice. At lower energy, the shoulder of the 2p 3/2 peak can be observed at 852.8 eV 28. This indicates the presence of traces of elemental nickel on the surface.…”

Supported Co catalysts prepared as thin films by magnetron sputtering for sodium borohydride and ammonia borane hydrolysis

“…These B-O based species were detected in B1s and O1s levels together with Na 1s signal from XPS on the used catalyst after cycle 4 (Table 3) and by SEM images as a film (Fig 8.b). After diluted acid washing, the catalytic activity was recovered (cycle 5) despite the XPS characteristic signals of B-O species were still present in the catalyst (191.9 eV, Table 3 bonds assigned according to Ref [18] and [37]) and SEM micrographs (Fig 8.c) show partial recovery of the structural features of A c c e p t e d M a n u s c r i p t the fresh catalyst (Fig 8.a). Quantification of the XPS spectra permitted to calculate B/Co ratio before and after acid washing.…”

Epitaxial growth of ultra-thin NiO films on Cu(111)

“…Under these conditions, different authors reported epitaxial NiO films. The electronic structure [8,10,[14][15][16][18][19][20] as well as the crystal structure [7,12,17] were investigated. More recently, NiO ultra-thin films grown by molecular beam epitaxy (MBE) at room temperature [8,18] have also been characterized.…”