NO adsorption and reaction on single crystal rutile TiO2(110) surfaces studied using UHV–FTIRS

Abstract

The adsorption and reaction of NO on both the oxidized and reduced single crystal rutile TiO₂(110) surfaces were studied in a UHV–FTIRS system at low temperature. The monodentate adsorption configuration of the cis-(NO)₂ dimer at bridge oxygen vacancy (Vo) sites was detected for the first time on reduced TiO₂(110) surfaces. With the aid of (NO)₂ dimer adsorption anisotropy, the bidentate configuration of the cis-(NO)₂ dimer on fivefold coordinated Ti_5c⁴⁺ cation sites was clearly confirmed. The (NO)₂ dimer converts to N₂O on Ti_5c⁴⁺ cation sites at higher NO dosage on both oxidized and reduced surfaces, rather than at Vo sites. The (NO)₂ → N₂O conversion is independent of the presence of Vo on TiO₂(110) surfaces. To explain the signs of absorption bands of the dimer monodentate configuration, the local optical constant at Vo sites was introduced.