Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 8: Oxides and insulators: Adsorption I

O 8.2: Talk

Monday, March 14, 2011, 11:30–11:45, WIL C307

DFT study of the Interaction of Hydrogen with ZnO(1010) Surfaces — •Jakub Goclon and Bernd Meyer — Interdisciplinary Center for Molecular Materials ICMM and Computer-Chemistry-Center CCC, University of Erlangen-Nürnberg, Germany

Understanding the interaction of hydrogen with ZnO is of fundamental interest in view of its widespread use in heterogeneous catalysis for hydrogenation and dehydrogenation reactions. Using DFT calculations in combination with a thermodynamic analysis we have calculated the relative stability of various structural models of the mixed-terminated nonpolar ZnO(1010) surface as a function of hydrogen and water chemical potentials. The coverage dependence of heterolytic hydrogen adsorption on O and Zn sites as well as surface hydroxylation via homolytic hydrogen and dissociative water adsorption were taken into account. From the adsorption energies a phase diagram of the lowest energy adsorbate structures in thermodynamic equilibrium with hydrogen and water reservoirs is constructed. It is found that at low hydrogen coverage only OH groups are formed, leading to a reduction of ZnO. However, as soon as a critical degree of reduction is reached, heterolytic hydrogen adsorption becomes more favorable, and at very hydrogen rich conditions a structure in which all surface O and Zn atoms are saturated with hydrogen is the most stable one. On the other hand, in water rich conditions a surface structure with a full zinc hydroxide layer is predicted to be the lowest energy structure.