The adsorption and thermal activation of 3-bromocyclohexene on Pt(111)
was studied by temperature programmed desorption (TPD), high-resoluti
on electron energy loss spectroscopy (HREELS), and X-ray photoelectron
spectroscopy (XPS). Upon adsorption, the first layer of 3-bromocycloh
exene dissociatively adsorbs to make Br-Pt and C6H9-Pt bonds and produ
ces benzene upon thermal activation. At higher coverages, 3-bromocyclo
hexene molecularly adsorbs and desorbs as the temperature increases, A
t lower coverages, the second layer molecular desorption peak at 192 K
is distinct from the multilayer desorption peak at 173 K, but as the
total coverage grows, the second layer shifts into the multilayer. Fol
lowing molecular desorption, C, symmetric pi-allylic C6H9 species rema
in on the surface and are stable until 250 K, where they dehydrogenate
to benzene; the dehydrogenation is rapidly completed by 280 K. Most o
f the benzene desorbs above 300 K, but a small amount decomposes to Cx
Hy species above 400 K to form surface carbide. The surface Br either
captures H generated by the dehydrogenation and leaves the surface as
HBr between 220 and 280 K or recombines as Br-2 above 500 K.