Application of surface-enhanced infrared absorption spectroscopy to investigate pyridine adsorption on platinum-group electrodes

In situ surface-enhanced infrared absorption spectroscopy (SEIRAS) was applied to investigate adsorption configurations of pyridine (Py) on platinum, palladium, ruthenium, and rhodium nanoparticle film electrodes. The results reveal that alpha-pyridyl species predominantly form on Pt electrodes by assuming an edge-on configuration with its ring N and alpha-C atoms bonding to the Pt surface, while on Ru and Rh electrodes pyridine molecules essentially remain intact by adopting a slightly edge-tilted configuration through bonding with its N lone pair electrons. Py adsorption on a Pd electrode may lie in between the above two cases; both alpha-pyridyl species and edge-tilted intact pyridine could be significantly present. Further comparison of the typical adsorption configurations on the above four electrodes with those on Ag, An, Cu, Cd, and Ni film electrodes suggests that valence electrons and the periodic row of metals may play an important role in determining the adsorption configuration.