The interaction of ethane, propane, isobutane, and neopentane with the (110) surface of iridium

Abstract

The adsorption and reaction of ethane, propane, isobutane, and neopentane with the reconstructed Ir (110)–(1×2) surface have been studied with the thermal description mass spectrometry. As the surface is heated, these hydrocarbons decompose to yield gaseous hydrogen and adsorbed carbon. No hydrocarbons other than the hydrocarbon initially adsorbed was observed to desorb under any of the conditions described in this investigation. The reactivity of the surface for the dissociation of the saturated hydrocarbons is linearly related to the availability of vacant β2 hydrogen adsites on the surface. Three thermal desorption states of hydrogen, identified as the α, β′2, and γ thermal desorption states, were observed following the dissociation of propane, isobutane, and neopentane. The α and γ thermal desorption states are hydrogen molecules desorbing from the surface following the dehydrogenation of hydrocarbon fragments on the surface, and the β′2 thermal desorption state represents hydrogen atoms that are bound to the metal surface in sites that are similar to the β2 adsites of hydrogen on the clean surface. The thermal desorption of hydrogen following exposure of the surface to ethane exhibits only a β′2 thermal desorption peak.