In situ surface-enhanced IR absorption spectroscopy on the adsorption and reduction of nitric oxide at ruthenium electrode

Real-time attenuated total-reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), in conjunction to cyclic voltammetry, was applied to investigate the adsorption and reduction of nitric oxide at Ru electrode in acidic solutions. For a NO-predosed Ru electrode, only one band located at 1840–1874 cm−1 was detected in 0.1 M HClO4, attributable to atop NO coadsorbed with oxygen-containing species [designated ν2ν2(O)NO species]. For a Ru electrode in 0.1 M HClO4 containing 20 mM NaNO2, two IR bands were observed at 1850–1886 cm−1 and 1740–1790 cm−1. The former, predominant at relatively high potentials, is ascribable to the ν2ν2(O)NO species; the latter, to atop NO adsorbed on nominal Ru sites at relatively low potentials (designated ν2ν2-NO species). In addition, a very weak band at 1520–1578 cm−1 may be assigned to multicoordinated NO coadsorbed with oxygen-containing species. The real-time spectral results suggest that the reduction of NO molecules and the coadsorbed oxygen-containing species proceed simultaneously rather than separately.