Unexpected Nondissociative Binding of N2O on Oxygen Vacancies on a Rutile TiO2(110)-1×1

Abstract

The interaction of N2O with oxygen vacancies (VO’s) on a partially reduced rutile TiO2(110)-1×1 surface was investigated using temperature-programmed desorption (TPD). Contrary to a common belief that VO on a rutile TiO2(110) is a dissociation site for N2O, our results indicate that N2O does not dissociate to form N2(g) and O(a). In TPD, N2O desorption shows two peaks with maxima at 135 and 175 K that are assigned to N2O desorption from Ti4+ and VO sites, respectively, with absolute coverages determined to be 5.4 × 1014 N2O/cm2 and 2.3 × 1013 N2O/cm2, respectively, on the TiO2(110)-1×1 surface used (VO concentration of 5%, 2.6 × 1013/cm2). When VO’s are passivated by dissociative adsorption of H2O, the N2O desorption peak at 175 K disappears, evidencing that the peak is related to VO-bonded N2O. The absence of N2O dissociation on VO’s is supported by a number of observations. First, the integrated amount of N2O desorbed from the substrate during TPD vs the amount of N2O dosed at 70 K shows a straight line...