| Title | Surface Photochemistry of Adsorbed Nitrate: The Role of Adsorbed Water in the Formation of Reduced Nitrogen Species on α-Fe2O3 Particle Surfaces. |
| Publication Type | Journal Article |
| Year of Publication | 2014 |
| Journal | Journal of Physical Chemistry A |
| Volume | 118 |
| Issue | 1 |
| Pagination | 158 - 166 |
| Authors | Nanayakkara, Charith E., Pradeep M. Jayaweera, Gayan Rubasinghege, Jonas Baltrusaitis, and Vicki H. Grassian |
| Publisher | American Chemical Society |
| ISBN Number | 1089-5639 |
| Keywords | surface photochem nitrate nitric acid adsorbate iron oxide particle |
| Abstract | The surface photochem. of nitrate, formed from nitric acid adsorption, on hematite (α-Fe2O3) particle surfaces under different environmental conditions is investigated using XPS. Following exposure of α-Fe2O3 particle surfaces to gas-phase nitric acid, a peak in the N1s region is seen at 407.4 eV; this binding energy is indicative of adsorbed nitrate. Upon broadband irradn. with light (λ > 300 nm), the nitrate peak decreases in intensity as a result of a decrease in adsorbed nitrate on the surface. Concomitant with this decrease in the nitrate coverage, there is the appearance of two lower binding energy peaks in the N1s region at 401.7 and 400.3 eV, due to reduced nitrogen species. The formation as well as the stability of these reduced nitrogen species, identified as NO- and N-, are further investigated as a function of water vapor pressure. Addnl., irradn. of adsorbed nitrate on α-Fe2O3 generates three nitrogen gas-phase products including NO2, NO, and N2O. As shown here, different environmental conditions of water vapor pressure and the presence of mol. oxygen greatly influence the relative photoproduct distribution from nitrate surface photochem. The atm. implications of these results are discussed. [on SciFinder(R)] |