H_2O chemisorption and H_2 oxidation on yttria-stabilized zirconia: Density functional theory and temperature-programmed desorption studies

摘要

The mechanism of H_2O 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 H_2O 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 H_2O/YSZ and the H_2/YSZ + O heterogeneous reaction systems noticeable amounts of H_2O are "dissolved" in the bulk as interstitial hydrogen and hydroxyl species. The experimental H_2O desorption data is used to access the accuracy of the H_2/H_2O/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) Bl004]. Finally a refined experimentally validated H_2/H_2O/YSZ adsorption/desorption and surface reaction kinetics data set is presented.