Surface-Enhanced Infrared Absorption Spectroscopic Studies of Adsorbed Nitrate, Nitric Oxide, and Related Compounds. 3. Formation and Reduction of Adsorbed Nitrite at a Platinum Electrode

The formation, potential-dependent structural change, and reduction of adsorbed nitrite at a platinum electrode were examined in 0.1 M HClO4 and 0.1 M NaClO4 by surface-enhanced infrared absorption spectroscopy (SEIRAS). The band assigned to the symmetric NO2 stretch of the nitro form of nitrite appeared at around 1300 cm−1 in both solutions. The potential dependence of the spectra revealed that this adsorbed nitrite is converted to NO adsorbed at on-top, bridge, and defect sites via IR-inactive surface nitrite species. In 0.1 M HClO4, these three adsorbed NO species were also formed during the adsorption process from the solution NO formed by the disproportionation of nitrite. In addition to the reduction via the IR-inactive surface nitrite species, a direct conversion from adsorbed nitrite to adsorbed NO was also suggested in 0.1 M HClO4.