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

Abstract

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 H₂ 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.

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