Two consecutive Eley–Rideal reaction steps in a D atom/adsorbate interaction: from methylene iodide via methyl iodide to methane

The interaction of gaseous D atoms with methylene iodide molecules adsorbed on graphite monolayer covered Pt(111) surfaces was studied using direct product rate measurement. At 85 K methane was observed as a reaction product from two consecutive D/adsorbate reaction steps. Via D addition to methylene iodide, adsorbed methyl iodide is formed as an intermediate. Subsequently, D abstracts methyl from methyl iodide towards methane. Approaching and passing the methyl iodide intermediate desorption temperature of 135 K during the reaction, the desorption of the intermediate prevents methane production. The kinetics of methane and intermediate methyl iodide formation is in agreement with the operation of Eley–Rideal reaction steps. This is in accordance with the expectation that on a substrate with a flat adsorption well for atoms from the gas phase the Eley Rideal mechanism should operate in atom/adsorbate reactions.