Modifying surface reactivity by carbide formation: Reaction pathways of cyclohexene over clean and carbide-modified W(111)

The decomposition and dehydrogenation of cyclohexene (c-C6H10) are used as probe reactions to compare the surface reactivities of clean and carbide-mo dified 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 spectrosc opy (HREELS), and near-edge X-ray absorption fine structure (NEXAFS). On th e 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.