Reactions of pyrrole with Ni(100)

The reactions of pyrrole with a clean Ni(100) surface have been studied with temperature programmed reaction (TPR), reflection absorption infrared spectroscopy (RAIS), and Auger electron spectroscopy (AES). RAIS indicated that pyrrole adsorbs on clean Ni(100) at 200 K with its ring parallel to the surface, presumably via π-bonding with the 1A₂ orbital. During TPR experiments with a heating rate of 8 K/s, pyrrole desorbs molecularly at 235 K and dihydrogen evolves above room temperature, in accord with equilibrium thermodynamics. During TPR experiments with a heating rate of 45 K/s, new pathways emerge. Light gases, principally HCN, H₂, and NH₃, desorb at circa 570 K. The variation of pyrrole decomposition products with slightly different heating rates suggests a change from a decomposition reaction to a polymerization reaction with increasing heating rates.