Facile H–D exchange in adsorbed methylidyne on Pt{110}–(1×2) and deuteration to gaseous methane

Hydrogen–deuterium exchange in adsorbed methylidyne, CHa, on Pt{110}–(1×2) has been studied for the first time using supersonic D2/H2 molecular beams, which provides new insights into the reversible hydrogenation of adsorbed hydrocarbon fragments. The exchange reaction is extremely facile at surface temperatures of 350–450 K and proceeds via a Langmuir–Hinshelwood reaction between Da and a CHa fragment to produce gas phase H2 and HD. The CDa+Ha (i.e., reverse) reaction was also studied and was found to proceed more slowly. Both exchange reactions were successfully modeled and the difference in reaction rates is explained using zero point energy differences alone. Finally, we demonstrate that with high incident D2 fluxes CHa can be completely deuterated to produce gaseous CHD3 and CD4.