An infrared study of acid sites on carbons by pyridine adsorption

Abstract The acidic properties of carbon films have been investigated by means of the IR spectroscopy of adsorbed pyridine. In the studies, carbon films have been used differing in the chemical structure of surface functional groups. Besides physically adsorbed molecules, pyridine can be adsorbed via hydrogen bonding interactions with surface hydroxyl groups and may be associatively bound to Lewis acidic surface sites. No evidence for Bronsted acidity of surface hydroxyl groups could be detected. These results reveal clearly that the protons responsible for the OH stretching bands are not acidic enough to interact with pyridine. The effect of Na+ poisoning on the pyridine adsorption is discussed.