Influence of Strain on Acid-Basic Properties of Oxide Surfaces

The surface of oxide nanostructures (nanoparticles, nanowires, and epitaxial thin films) can be significantly strained compared to the regular crystallographic surfaces. In this work, using density functional theory methods, we studied the dependence of properties of MgO(100), CaO(100), SrO(100), BaO(100), anatase TiO2(101), and tetragonal ZrO2(101) surfaces (band gap, work function) on external tensile and compressive strain from +4 to-4%. To probe the acid sites, the adsorption of CO as a probe molecule was investigated. In most cases, tensile strain favors the adsorption of CO, while compressive strain weakens it. To also probe the anionic basic sites, we used H2O as a probe molecule. On most surfaces, two competing adsorption modes (molecular and dissociative) are present. Applying strain has a different effect on the adsorption modes. On t-ZrO2, we can invert the stability order of molecular and dissociative adsorption by applying 1.4% biaxial tensile strain. We described the dependency of different properties on strain with a simple empirical model with only three fitting parameters. This allows for a precise interpolation of our data and gives the opportunity to predict surface properties of strained surfaces.