Modifying Surface Reactivity by Carbide Formation: Reaction Pathways of Cyclohexene over Clean and Carbide-Modified W(111)

The decomposition and dehydrogenation of cyclohexene (c-C 6 H 10 ) are used as probe reactions to compare the surface reactivities of clean and carbide-modified W(111). The reaction mechanisms have been studied using temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy (HREELS), and near-edge X-ray absorption fine structure (NEXAFS). On the clean W(111) surface, cyclohexene molecules decompose to produce hydrogen, atomic carbon and cyclohexane. In contrast, on the carbide-modified W(111) surface, cyclohexene undergoes primarily dehydrogenation to form benzene and hydrogen. The selectivity to the production of gas-phase benzene on C/W(111) is similar to that observed on the Pt(111) surface.