AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuM

Paper SS1-TuM4
Chemistry of SO@sub 2@ and NO@sub 2@ on ZnO(0001)-Zn and ZnO Powders: Changes in Reactivity with Surface Structure and Composition

Tuesday, October 3, 2000, 9:20 am, Room 208

Session: Reactions on Oxides and Environmental Chemistry
Presenter: J.A. Rodriguez, Brookhaven National Laboratory
Authors: J.A. Rodriguez, Brookhaven National Laboratory
T. Jirsak, Brookhaven National Laboratory
J. Dvorak, Brookhaven National Laboratory
J. Hrbek, Brookhaven National Laboratory
Correspondent: Click to Email
Synchrotron-based photoemission and x-ray absorption spectroscopy have been used to study the interaction of SO@sub 2@ and NO@sub 2@ with ZnO(0001)-Zn and polycrystalline surfaces of zinc oxide (films and powders). Important differences are observed when comparing the behavior of the adsorbates on these oxide surfaces. These differences are in a part a result of changes in structural properties (flat vs rough surfaces), but in some cases they clearly originate in variations in surface composition (Zn-adsorbate vs O-adsorbate interactions). For example, the Zn-terminated (0001) face of ZnO interacts weakly with SO@sub 2@ (desorption temperature of adsorbate < 200 K). In contrast, the SO@sub 2@ molecules interact readily with O sites of Ar@super +@ sputtered ZnO(0001)-Zn or polycrystalline ZnO forming very stable SO@sub 3@ species. Due to its radical nature, adsorbed NO@sub 2@ is more chemically active than SO@sub 2@. After dosing nitrogen dioxide to ZnO(0001) at 100 K, chemisorbed NO@sub 2@ and NO@sub 3@ coexists on the surface. Partial transformation of NO@sub 2@ into NO@sub 3@ is observed from 150 to 300 K. The data for the NO@sub 2@/ZnO(0001)-Zn system clearly prove that large quantities of NO@sub 3@ can be formed on metal sites of an oxide surface as a consequence of partial decomposition or disproportionation of NO@sub 2@.