Adsorption and thermal decomposition of n-azopropane on Pt(111)

The adsorption and thermal decomposition of n-azopropane on Pt (111) were studied by using temperature-programmed desorption (TPD) and reflection-absorption infra-red spectroscopy (RAIRS). At low temperatures, n-azopropane chemisorbs molecularly on Pt(111), but it isomerizes into a cis configuration upon bonding to the surface and changes its adsorption orientation as a function coverage. Multilayer and monolayer molecular desorption occur about 130 and 170 K, respectively, and a new surface species -probably dipropyl hydrazine - forms upon annealing the remaining chemisorbed molecules above 175 K. Further heating of the sample leads to the desorption of small amounts of propylene and ethylene, at 240 and 275 K, respectively. Another surface transformation is identified by RAIRS around 275 K, possibly the conversion to an imine-type species, and propionitrile and small amounts of propyl and methyl amines are produced soon after that; they desorb at 320 and 330 K, respectively. Finally, a more extensive dehydrogenation of the remaining surface species takes place, and HCN desorbs in two stages around 525 and 600 K. The chemistry of propionitrile and propyl amine was also explored briefly by RAIRS and TPD for reference.