Adsorption and decomposition of CH3NO2 on a polycrystalline Pt foil using TPD, MBRS, XPS and FT-RAIRS

The adsorption and decomposition of nitromethane (CH3NO2) on a polycrystalline Pt foil has been studied using a combination of temperature-programmed desorption (TPD), molecular beam reactive scattering (MBRS), and X-ray photoelectron (XPS) and Fourier-transform-reflection/absorption IR (FT-RAIRS) spectroscopies. Adsorption at 100 K is predominantly molecular, with multilayers of physisorbed CH3NO2 desorbing at 140 K and the first monolayer at 170 K. Adsorption at 300 K leads to complete dissociation of nitromethane to yield CO, NO, and H-2 as major desorption products, C2N2, and CH4, H2O and CO2 as minor desorption products. MBRS experiments reveal that some molecular H2O is also formed following adsorption at 300 K, but the surface lifetime of H2O at 300 K is relatively short and spontaneous desorption occurs at this temperature. The possible involvement of a nitrite intermediate in the thermal decomposition at 300 K and also under XPS acquisition conditions at lower temperatures is discussed.