Species formed after NO adsorption and NO + O2 co-adsorption on TiO2: an FTIR spectroscopic study

Abstract

Adsorption of NO and its co-adsorption with oxygen on TiO₂ (Degussa P-25) were studied by FTIR spectroscopy. It was found that NO adsorption results in its disproportionation to NO⁻ (1170 cm⁻¹), N₂O₂ ²⁻ (1335 cm⁻¹) and nitrates (1650–1550 and 1240–1220 cm⁻¹). The nitrate bands develop with time and coordinated NO (ca. 1900 cm⁻¹) is formed. Addition of oxygen to NO results in a strong increase in concentration of the nitrates and formation of NO⁺ (2206 cm⁻¹). In addition, species assigned to nitrocomplexes (1520 and 1284 cm⁻¹) are found. The stability and reactivity of the different surface compounds as well as their interconversion are studied and discussed.