The adsorption of nitrogen dioxide (NO2) on Pt(111) has been investigated using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). At 100 K, NO2 is adsorbed molecularly at all coverages to form a Pt(111) μ-N,O-nitrito surface complex. This puts NO2 in an upright bridge-bonded configuration with Cs symmetry. Our assignment of this surface species is supported by the infrared spectrum of a μ-N,O-nitritoplatinate complex. The saturation coverage of chemisorbed NO2 is about 0.5 monolayers (ML) at 100 K. At low coverages, θNO2<0.25 ML, adsorption is irreversible and NO2 dissociates completely by 285 K to O atoms and NO. However, at coverages greater than θNO2=0.25 ML, the adsorption is partially reversible and NO2 desorbs molecularly with first-order kinetics with Ea=19 kcal/mol. About 20% of the NO2 adsorbs reversibly at saturation coverage. With higher exposures of NO2, a condensed multilayer of N2O4 can be formed.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry