| AVS 54th International Symposium | |
| Surface Science | Wednesday Sessions |
| Session SS1-WeM |
| Session: | Oxide Surface Reactivity |
| Presenter: | D.E. Starr, Lawrence Berkeley National Laboratory |
| Authors: | D.E. Starr, Lawrence Berkeley National Laboratory Ch.D. Weiss, Lawrence Berkeley National Laboratory S. Yamamoto, Stanford Synchrotron Radiation Laboratory A. Nilsson, Stanford Synchrotron Radiation Laboratory M. Salmeron, Lawrence Berkeley National Laboratory H. Bluhm, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
NOx compounds are very harmful environmental contaminants commonly formed in combustion processes. Their adsorption onto the surfaces of alkaline-earth metal-oxides has recently received a great deal of attention due to the use of alkaline-earth metal-oxides as NOx storage compounds for controlling emissions during combustion under fuel-lean conditions. In this work we have studied the adsorption of NO2 on MgO(100) films grown on Ag(100) using photoemission spectroscopy. Many of the previous experimental studies of this system were performed at low temperatures with subsequent thermal heating under Ultra-High Vacuum conditions. In this study we have used the Ambient Pressure Photoemission Spectroscopy experiment at Beamline 11.0.2 of the Advanced Light Source to study the adsorption and reaction of NO2 onto MgO(100) at 300 K and 10-6 torr NO2 pressures for exposures ranging from a few Langmuir up to twenty thousand Langmuir. At these conditions, we find that the NO2 initially adsorbs as NO2 with low coverage (~0.05 ML). Upon increasing exposure, we observe a reduction in the coverage of NO2 and the presence of adsorbed NO3. Further, at high exposure we find increasing coverage of NO3 (~0.30 ML) without the presence of NO2 on the surface. This indicates that the production of NO3 on the surface likely occurs via initial NO2 dissociation which produces adsorbed O which then oxidizes NO2 to form NO3.