A Photoemission Study of Ethylene Decomposition on a Co(0001) Surface: Formation of Different Types of Carbon Species

We have studied the interaction of ethylene on Co(0001) in detail by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). At 130 K, the chemisorption and decomposition of C 2 H 4 were found to depend on the vacant sites available on Co(0001). C 2 H 4 chemisorbs dissociatively at low exposures but both dissociatively and molecularly at large exposures. Upon heating, some C 2 H 4 (a) desorbs molecularly from the surface, releasing vacant surface sites that result in the simultaneous decomposition of other C 2 H 4 (a). C 2 H 2 (a) is the surface intermediate for the decomposition of C 2 H 4 (a) on Co(0001). At elevated temperatures, C 2 H 2 (a) simultaneously undergoes the direct dehydrogenation and the cyclopolymerization–dehydrogenation to form surface C 2 cluster and graphitic carbon on Co(0001). At 500 K, C 2 H 4 directly decomposes on Co(0001), forming surface atomic carbon. These results provide novel information on the chemisorption and decomposition of C 2 H 4 on Co(0001) and the nature of resulted carbon species, greatly deepening our fundamental understanding of the relevant heterogeneous catalytic reactions catalyzed by Co-based catalysts and the growth of graphene on Co surfaces by chemical vapor deposition.