| AVS 55th International Symposium & Exhibition | |
| Surface Science | Friday Sessions |
| Session SS+AS+NC-FrM |
| Session: | Environmental Surfaces and Water Interaction with Oxide Surfaces |
| Presenter: | M.A. Brown, University of California, Irvine |
| Authors: | M.A. Brown, University of California, Irvine T.M. McIntire, University of California, Irvine M.J. Krisch, University of California, Irvine V. Johánek, University of Virginia P.D. Ashby, Lawrence Berkeley National Laboratory Z. Liu, Lawrence Berkeley National Laboratory A. Mehta, Stanford Linear Accelerator Center D.F. Ogeltree, Lawrence Berkeley National Laboratory M. Salmeron, Lawrence Berkeley National Laboratory J.C. Hemminger, University of California, Irvine |
| Correspondent: | Click to Email |
Sea salt aerosols are known to undergo heterogeneous reactions with atmospheric oxidants, resulting in halide depletion as they travel through polluted regions of the environment. The subsequent photochemistry of halide compounds (including halogenated oxides) strongly influences the chemical composition of the atmosphere. The results from uptake measurements of O3 and OH radical on potassium iodide will be discussed. The reactivity of KI with O3 and OH radical are remarkably different and result in reaction products of KIO3 and KOH, respectively. We describe results from X-ray photoemission spectroscopy, X-ray diffraction, Atomic Force Microscopy and IR spectroscopy. In the case of O3, under conditions in which the KI surface is devoid of adsorbed water molecules the reaction is self-passivating, and results in a thin layer of KIO3 with an rms roughness of 3.6 nm. Subsequent exposure to water vapor mobilizes the KIO3 oxide layer, revealing additional KI substrate that is readily available for further oxidation. As such, under conditions of low relative humidity the uptake of O3 onto KI is not expected to be self-passivating. Under similar conditions, the reaction of OH radical with KI results in halide vacancies (iodide is released into the gas phase) created in the outermost surface lattice sites. The iodide vacancies are filled with OH- to generate a layer of KOH that is self-passivating following prolonged exposures. There is no spectroscopic evidence of stable oxidized iodide reaction products. AFM and IR results will also be discussed.