The unusual adsorption behaviour of benzene on Co(10(1)over-bar0)

Adsorption of benzene on Co(10 (1) over bar 0) leads to formation of an ordered p(3 x 1) monolayer. ARPES measurements combined with adlayer density considerations indicate that the Co(10 (1) over bar 0)-p(3 x 1) monolayer consists of molecules whose symmetry has been reduced to C-1 consistent with a partially dehydrogenated tilted cyclic Ca intermediate (phenyl or C6H4). Desorption measurements in conjunction with ARPES indicate that a stepwise dehydrogenation of the ring occurs with the dehydrogenation step above room temperature at similar to 380 K corresponding to formation of small well-oriented CxHy (x,y = 1 or 2) hydrocarbon fragment(s) (possibly C2H and CH) resulting from ring opening. Complete dehydrogenation occurs for temperatures above 550 K, leaving a carbonaceous residue. The low dehydrogenation and decomposition temperatures indicate Co(10 (1) over bar 0) to be particularly active towards both C-H bond scission and ring opening.