Adsorption and reaction of nitric oxide with atomic oxygen covered Au(111)

Molecular beam scattering techniques were employed to investigate the adsorption/reaction of NO with an atomic oxygen covered Au(111) surface to form nitrogen dioxide, NO2. Results suggest that at temperatures above Ts approximate to 200 K, the NO2 production is limited by NO surface lifetime on O/Au(111); at temperatures below T-s approximate to 200 K NO2 production is limited by both a reduction in the NO2 reaction rate and NO2 desorption limitations. Collision induced desorption (CID) and temperature programmed desorption (TPD) spectra provide evidence that suggests nitric oxide may react with chemisorbed oxygen atoms at temperatures as low as T-s 85 K. A simple kinetic model was employed to estimate the activation energy (E-r approximate to 0.21 +/- 0.02 eV) of this reaction on the Au(111) surface with an atomic oxygen coverage of theta(o) approximate to 0.95 ML. These results illustrate that while bulk gold surfaces are generally considered to be catalytically inert, the presence of chemisorbed atomic oxygen significantly increases the adsorption/reactive properties of the Au(111) surface toward gas-phase nitric oxide.