Surface-enhanced infrared absorption spectroscopic studies of adsorbed nitrate, nitric oxide, and related compounds 2: Nitrate ion adsorption at a platinum electrode.

The adsorbed species formed from the nitrate ion were examined using surface-enhanced infrared absorption spectroscopy (SEIRAS). The main band was observed at 1547-1568 cm-1 at 0.2 V in 0.01 M NaNO3 + 0.1 M HClO4. Although this band is close to that assigned to the adsorbed NO in the literature, it is assigned to the N=O stretching vibration of the chelating bidentate form of nitrate for the following reasons. (i) Nitrate gives a single band, while NO has three bands independent of the coverage. (ii) The band intensity remained constant in the potential range from 0.1 to 0.6 V, while that of the bridged NO at around 1600 cm-1 decreased in this range. (iii) The rate constants for the reduction and/or desorption at negative potentials are about 3 times higher than those of the bridged NO. (iv) The adsorbed species from nitrate is replaced with CO more easily than the bridged NO.