Adsorption of NO on the TiO2(110) Surface: An Experimental and Theoretical Study

Abstract

The chemisorption properties of NO on the oxidized TiO2(110) surface have been investigated using both experimental and theoretical methods. The results of temperature-programmed desorption measurements indicate that for NO exposures less than 1.1 × 1014 molecules/cm2 NO adsorbs weakly and desorbs at ∼127 K. The thermal desorption kinetics are almost independent of the coverage of adsorbed NO molecules. The experimental activation energy for NO desorption from the nondefective TiO2(110) surface is 8.4 kcal/mol in the limit of zero coverage. Above a critical NO surface exposure of 5.5 × 1014 molecules/cm2, partial conversion of NO to N2O is observed yielding N2O desorption processes at ∼169 and ∼250 K. The weak interaction between the NO molecule and the TiO2(110) surface has been also revealed from first-principles calculations based on density functional theory and the pseudopotential method in which NO molecules are adsorbed at the in-plane Ti cation sites. These calculations employ slab geometry and pe...