AVS 46th International Symposium
    Surface Science Division Monday Sessions
       Session SS1+EM-MoM

Paper SS1+EM-MoM6
Interactions of HCOOH with Stoichiometric and Defective SrTiO@sub 3@(100) Surfaces

Monday, October 25, 1999, 10:00 am, Room 606

Session: Chemistry on Oxides
Presenter: L. Wang, Pacific Northwest National Laboratories
Authors: L. Wang, Pacific Northwest National Laboratories
F. Ferris, Pacific Northwest National Laboratories
H. Engelhardt, Pacific Northwest National Laboratories
Correspondent: Click to Email
Interactions of HCOOH with stoichiometric (nearly defect-free) and defective SrTiO@sub 3@(100) surfaces have been studied using x-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and electronic structure calculations. Two reaction pathways were observed for formaldehyde formation from formic acid on SrTiO@sub 3@(100) surfaces. On stoichiometric surfaces, formaldehyde was produced through bimolecular coupling of two formates. However, on Ar+ sputtered surfaces, formaldehyde formation involves the reduction of surface formate by the oxidation of reduced Ti cations. XPS results show that surface defects on sputtered SrTiO@sub 3@(100) surfaces were reoxidized significantly upon exposure to 30 L HCOOH at 300 K, in contrast to defects on sputtered TiO@sub 2@(110) surfaces where no reduction in defect intensity was observed under the same condition. The fact that surface formate was reduced at 300 K on SrTiO@sub 3@(100) is clearly evident in TPD data where the desorption peak of formaldehyde is shifted to a lower temperature and broadened significantly down to 300 K for Ar+ sputtered SrTiO@sub 3@(100) surfaces as compared with stoichiometric surfaces. Electronic structure calculations have been used to investigate the adsorptive interactions for formate and formaldehyde on the cation sites of both stoichiometric and defective SrTiO@sub 3@(100) surfaces. The results for formate indicate a strong adsorptive interaction consistent with the experimental observations, with significant charge redistribution. Further results will be discussed in terms of potential reaction mechanisms.