H2O chemisorption and H2 oxidation on yttria-stabilized zirconia: Density functional theory and temperature-programmed desorption studies

The mechanism of H2O dissociation as well as the adsorption and oxidation reaction of H-2 on yttria-stabilized zirconia (YSZ), commonly used as part of solid oxide fuel cell (SOFC) anodes, was investigated employing temperature-programmed desorption (TPD) spectroscopy and density functional theory (DFT). In agreement with theory the experimental results show that interaction of gaseous H2O with YSZ results in dissociative adsorption leading to strongly bound OH surface species. In the interaction of gaseous H-2 with an oxygen-enriched YSZ surface (YSZ + O) similar OH surface species are formed as reaction intermediates in the H-2 oxidation. Our experiments showed that in both the H2O/YSZ and the H-2/YSZ + O heterogeneous reaction systems noticeable amounts of H2O are "dissolved" in the bulk as interstitial hydrogen and hydroxyl species. The experimental H2O desorption data is used to access the accuracy of the H-2/H2O/YSZ adsorption/desorption and surface reaction kinetics data, employed in previous modeling studies of the electrochemical H-2 oxidation on Ni-pattern/YSZ model anodes by Vogler et al. [J. Electrochem. Soc., 156 (2009) B663] and Goodwin et al. [J. Electrochem. Soc., 156 (2009) B1004]. Finally a refined experimentally validated H-2/H2O/YSZ adsorption/desorption and surface reaction kinetics data set is presented. (C) 2010 Elsevier B.V. All rights reserved.