Temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) have been used to determine the NO2 adsorption energy and geometry in the presence of coadsorbed oxygen atoms on Pt(III) at 100 K. NO2 is adsorbed molecularly, regardless of the oxygen atom precoverage. Coadsorption with oxygen atoms causes a decrease in the amount of irreversible NO2 adsorption and also a decrease in the amount of the Pt(III) μ-N,O-nitrito surface complex (bridge-bonded NO2). Coadsorption also causes the formation of a new, low-temperature desorption state for NO2 which is associated with an NO2 bonding geometry possessing C2υ symmetry. It is proposed that this NO2 species is bonded to a platinum atom through the nitrogen atom in a nitro configuration. An NO3 species is not observed spectroscopically at any oxygen atom coverage in this work. However, an NO3 intermediate may be responsible for some of the features in the adsorption and desorption kinetics. At θo = 0.75 monolayer (ML), a chemisorbed NO2 saturation coverage of 0.15 ML can be achieved and all NO2 adsorption is reversible, having a chemisorption bond energy of 11 kcal/mol. When the chemisorbed state is saturated, an N2O4 multilayer can be formed at 100 K with greater NO2 exposures.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Surfaces and Interfaces