PNNL

Abstract

The impact of oxygen induced regrowth of TiO2 on the reduced rutile TiO2(110) surface has been studied using temperature programmed desorption (TPD) of adsorbed water multilayers. Pre-exposure of UHV annealed TiO2(110) surfaces to O2 at temperatures from 300 to 850 K induced changes in subsequent water TPDs that were interpreted in terms of the rougher surface morphologies resulting from the regrowth process. Water TPD from TiO2(110) previously oxidized at 300 K exhibited a new peak at *312 K due to reaction of water with O adatoms. These O adatoms were produced by dissociative adsorption of O2 at O-vacancy sites. Additionally, oxygen reacted (slowly) with surface Ti2O3 strands at RT. Water TPD from surfaces pre-oxidized at higher temperatures (P500 K) exhibited features reflective of desorption from rough surfaces, namely loss of peak resolution and eventual merger of the second layer and ice peaks, formation of a high temperature tail on the second layer peak, and broadening of the first layer TPD peak. The multiplicity of kinetically different adsorption sites on the roughened TiO2(110) surfaces contributed to the widening of the desorption features. Published by Elsevier B.V.