| Title | XPS study of nitrogen dioxide adsorption on metal oxide particle surfaces under different environmental conditions. |
| Publication Type | Journal Article |
| Year of Publication | 2009 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 11 |
| Issue | 37 |
| Pagination | 8295 - 8305 |
| Authors | Baltrusaitis, Jonas, Pradeep M. Jayaweera, and Vicki H. Grassian |
| Publisher | Royal Society of Chemistry |
| ISBN Number | 1463-9076 |
| Keywords | nitrogen dioxide adsorbed metal oxide surface species XPS, oxygen nitrogen dioxide adsorbed metal oxide surface species XPS, UV nitrogen dioxide adsorbed metal oxide surface species XPS, water nitrogen dioxide adsorbed metal oxide surface species XPS |
| Abstract | The adsorption of nitrogen dioxide on gamma aluminum oxide (γ-Al2O3) and alpha iron oxide (α-Fe2O3) particle surfaces under various conditions of relative humidity, presence of mol. oxygen and UV light has been investigated. XPS is used to monitor the different surface species that form under these environmental conditions. Adsorption of NO2 on aluminum oxide particle surfaces results primarily in the formation of surface nitrate, NO3- with an oxidn. state of +5, as indicated by a peak with binding energy of 407.3 eV in the N1s region. An addnl. minority species, sensitive to the presence of relative humidity and mol. oxygen, is also obsd. in the N1s region with lower binding energy of 405.9 eV. This peak is assigned to a surface species in the +4 oxidn. state. When irradiated with UV light, other species form on the surface. These surface-bound photochem. products all have lower binding energy, between 400 and 402 eV, indicating reduced nitrogen species in the range of N oxidns. states spanning +1 to -1. Co-adsorbed water decreases the amt. of these reduced surface-bound products while the presence of mol. oxygen completely suppresses the formation of all reduced nitrogen species on aluminum oxide particle surfaces. For NO2 on iron oxide particle surfaces, photoredn. is enhanced relative to γ-Al2O3 and surface bound photoreduced species are obsd. under all environmental conditions. Complementing the exptl. data, N1s core electron binding energies (CEBEs) were calcd. using DFT for a no. of nitrogen-contg. species in the gas phase and adsorbed on an Al8O12 cluster. A range of CEBEs is calcd. for various nitrogen species in different adsorption modes and oxidn. states. These calcd. values are discussed in light of the peaks obsd. in the XPS N1s region and the possible species that form following NO2 adsorption and photoreaction on metal oxide particle surfaces under different conditions of relative humidity, presence of mol. oxygen and UV light. [on SciFinder(R)] |