The adsorption of NO2 on Au(111) has been investigated using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). At 100 K, NO2 is adsorbed molecularly to form a Au(111) O,O'-nitrito surface chelate with C2v symmetry. The saturation coverage of chemisorbed NO2 is about 0.4 monolayers. The adsorption is reversible and NO2 desorbs with first-order kinetics and an activation energy of 14 kcal/mol. When the chemisorbed state is saturated, an N2O4 multilayer can be formed at 100 K with greater NO2 exposures. Also, when the chemisorbed NO2 surface chelate is exposed to NO at 100 K, N2O3 is formed on the surface in an upright configuration. While it is not clear whether NO2 chemisorbs on Au(111) as a radical, its reactivity towards gas-phase NO to produce adsorbed N2O3 shows that it is capable of undergoing radical-radical types of reactions. The reaction can be reversed by warming to 175 K implying that the N-N bond energy is approximately 10 kcal/mol. NO and N2O do not adsorb on Au(111) at 95 K. in ultrahigh vacuum.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry