Jinlong Gong1, Rotimi A. Ojifinni2, Nathan S. Froemming3, Ting Yan3, Graeme Henkelman4, and C. Buddie Mullins5. (1) Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712, (2) Center for Nano and Molecular Science and Technology and Texas Materials Institute, University of Texas at Austin, Austin, TX 78712, (3) Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712, (4) Department of Chemistry and Biochemistry, Center for Nano-and Molecular Science and Technology, and Texas Materials Institute, University of Texas at Austin, Austin, TX 78712, (5) Department of Chemical Engineering, Center for Nano-and Molecular Science and Technology, and Texas Materials Institute, University of Texas at Austin, Austin, TX 78712
The reactivity of atomic oxygen on Au(111) has been investigated employing molecular beam scattering and temperature programmed desorption (TPD) techniques under ultrahigh vacuum (UHV) conditions. We demonstrate that adsorbed O atoms (O
ad) facilitate NH
3,ad decomposition even though ammonia does not dissociate on the clean Au(111) surface. The selectivity of the catalytic oxidation of ammonia to N
2 or to NO on Au(111) is tunable by the amount of atomic oxygen pre-covering the surface. Both N
2 and NO are formed via simple recombination reactions (N
ad + N
ad and N
ad + O
ad). At low oxygen coverages (Θ
O < 0.5 ML), adsorbed ammonia is stripped to NH
x,ad which decomposes to form gaseous N
2.
We also present experimental and density functional theory (DFT) calculation results of formation and decomposition of the carbonate anion (CO3 = CO2 + Oad) on atomic oxygen pre-covered Au(111). A reaction probability on the order of 10-4 and an apparent activation energy of -0.15 eV are estimated for this reaction. The small values of reaction probability are likely part of the reason why an earlier study on Au(111) reported undetectable surface carbonate formation. Additionally, we have investigated partial oxidation of propanol on atomic oxygen covered Au(111). At reaction temperatures below 300 K, 1-propanol is oxidized to propaldehyde with 100% selectivity while acetone is the only products of 2-propanol partial oxidation. A small amount of CO2 is formed at higher surface temperatures (i.e., above 300 K).