XPS study of nitrogen dioxide adsorption on metal oxide particle surfaces under different environmental conditions

Abstract

The adsorption of nitrogen dioxide on gamma aluminium oxide (gamma-Al(2)O(3)) and alpha iron oxide (alpha-Fe(2)O(3)) particle surfaces under various conditions of relative humidity, presence of molecular oxygen and UV light has been investigated. X-Ray photoelectron spectroscopy (XPS) is used to monitor the different surface species that form under these environmental conditions. Adsorption of NO(2) on aluminum oxide particle surfaces results primarily in the formation of surface nitrate, NO(3)(-) with an oxidation state of +5, as indicated by a peak with binding energy of 407.3 eV in the N1s region. An additional minority species, sensitive to the presence of relative humidity and molecular oxygen, is also observed in the N1s region with lower binding energy of 405.9 eV. This peak is assigned to a surface species in the +4 oxidation state. When irradiated with UV light, other species form on the surface. These surface-bound photochemical products all have lower binding energy, between 400 and 402 eV, indicating reduced nitrogen species in the range of N oxidations states spanning +1 to -1. Co-adsorbed water decreases the amount of these reduced surface-bound products while the presence of molecular oxygen completely suppresses the formation of all reduced nitrogen species on aluminum oxide particle surfaces. For NO(2) on iron oxide particle surfaces, photoreduction is enhanced relative to gamma-Al(2)O(3) and surface bound photoreduced species are observed under all environmental conditions. Complementing the experimental data, N1s core electron binding energies (CEBEs) were calculated using DFT for a number of nitrogen-containing species in the gas phase and adsorbed on an Al(8)O(12) cluster. A range of CEBEs is calculated for various nitrogen species in different adsorption modes and oxidation states. These calculated values are discussed in light of the peaks observed in the XPS N1s region and the possible species that form following NO(2) adsorption and photoreaction on metal oxide particle surfaces under different conditions of relative humidity, presence of molecular oxygen and UV light.

Surface-enhanced redox chemistry of polysulphides on a metallic and polar host for lithium-sulphur batteries

“…5). We further note that binding energy shifts of a similar magnitude (1.1-3.8 eV) have been predicted on the basis of theory, and experimentally recorded, for anions such as NO x n À species adsorbed on alumina clusters 35 . The minor, broad background contribution between 166 and 169.5 eV on S 2p spectra (Fig.…”

Influence of relative humidity on heterogeneous kinetics of NO2 on kaolin and hematite

“…20 Besides surface nitrates and nitrites, 19,[29][30][31] HONO is also detected as a gaseous product. 6,11,18 Under ultra-violet irradiation, the HONO yield (y HONO ) is 75%, 33% and 80% for reactions of NO 2 on pure TiO 2 , 22 1% TiO 2 /SiO 2 and Saharan sand, 18 respectively.…”

Effect of N bonding structure in AlON deposited by plasma-assisted atomic layer deposition on electrical properties of 4H-SiC MOS capacitor

“…These spectra can be deconvoluted into three components with peaks at 403.2 ± 0.1, 398.5 ± 0.1, and 396.7 eV, which correspond to the chemical bonding states of Al-NO 2 , Al-NO, and Al-N, respectively, referring to a previous report. 30) Figure 9(b) shows the N content dependence of the composition of each chemical bonding component of N. Each composition was estimated from the ratio of the area intensity of each component to the total intensity of all elements (Al 2p, O 1s, and N 1s core levels) measured by XPS. The compositions of Al-N and Al-NO bonds increase with the N content.…”