The effect of carbide surface structure: Different reaction pathways of cyclohexene on C/W(1 1 0) and C/W(1 1 1)

We have investigated the reactivities of clean and carbide-modified W(1 1 0) surfaces by using the dehydrogenation and decomposition of cyclohexene as probe reactions. The reaction pathways have been studied using temperature programmed desorption, Auger electron spectroscopy, and high-resolution electron energy loss spectroscopy. On the clean W(1 1 0) surface, cyclohexene molecules undergo complete decomposition to produce hydrogen and atomic carbon. On the carbide-modified W(1 1 0) surface, only a fraction of cyclohexene undergoes dehydrogenation to produce gas phase benzene while the dominant reaction pathway remains to be the complete decomposition to atomic carbon and hydrogen. Overall the reactivity and product selectivity of cyclohexene on C/W(1 1 0) are very different from our previous studies on carbide-modified W(1 1 1). The comparison clearly indicates that the chemical properties of carbide-modified surfaces depend strongly on the structure of the metal substrates.