Adsorption and reaction of NO on oxidized and reduced SrTiO3(100) surfaces

Abstract

Adsorption and reaction of NO on oxidized and reduced SrTiO3(100) surfaces have been studied using temperature programmed desorption (TPD). Major desorption peaks for NO from the fully oxidized surface are found at 140 and 260 K, along with a long tail that continues up to 500 K. The desorption features at 140 and 260 K correspond to activation energies of 36 and 66 kJ/mol, respectively, using a simple Redhead analysis. NO reacts nondissociatively on the fully oxidized surface. Reactivity of reduced SrTiO3(100) is relatively higher than that of the fully oxidized surface and is influenced by the adsorption temperature of the NO molecules on the surface. NO and N2O are the major desorption products following adsorption of NO on the reduced surface at 110 K. Desorption of N2O from significantly reduced SrTiO3(100) indicates that the oxygen atoms of the adsorbed NO molecules are preferentially extracted by the surface oxygen vacancy sites, whereas the surface oxidizes as a result of the deoxygenation of the adsorbates. Adsorption of NO on the reduced surface at 297 K is followed by breakage of the N–O bond producing adsorbed N and O atoms and recombination of these adspecies results in desorption of NO and N2 from this surface. Adsorption of NO on the significantly reduced surface at 200 K is followed by desorption of NO, N2, and N2O as TPD products and the reactivity of this surface at 200 K presumably is a composite of the behavior observed for NO adsorption at 110 and 297 K.