Pyrrole adsorption and reaction on Mo(1Â 1Â 0) and C/N-Mo(1Â 1Â 0)

The adsorption of pyrrole (C4H5N) on Mo(1 1 0) and C/N-Mo(1 1 0) surfaces has been investigated using temperature-programmed desorption (TPD) and Auger electron spectroscopy (AES). Pyrrole adsorbs and decomposes on both Mo(1 1 0) and C/N-Mo(1 1 0) giving rise to surface carbon and nitrogen with no additional reaction products desorbing from the surface. Molecular pyrrole desorbs at an average temperature of 351 K with a corresponding first-order activation energy of 21.9 ± 0.6 kcal mol−1 independent of surface exposures over the range of 0.5-5 L. A low-temperature peak corresponding to multilayer pyrrole sublimation was observed at 4 L exposure at approximately 250 K (11.1 kcal mol−1) that increases in intensity upon 5 L exposure. Auger analysis following TPD indicted a C:N ratio of 4:1 at exposures less than 2 L and 2:1 at higher exposures. Based on the activation energies and surface analysis, it is suggested that pyrrole adsorbs flat-lying through the π-orbitals without any bond cleavage, while at higher surface exposures the coexistence of slightly tilted mode with a flat-lying mode is possible.