Ferroelectric surface chemistry: First-principles study of the PbTiO3 surface

Ferroelectric surfaces provide a promising method for modifying surface reactions via an external electric field, which can potentially provide an avenue for tunable molecular binding and surface catalysis. Using first-principles density functional theory, we investigate how the properties of the PbTiO3 surface vary with polarization and how these changes affect CO2 and H2O adsorption. We find that the polarized stoichiometric surfaces cancel the depolarizing field with an electronic reconstruction, which has a large effect on molecular binding energies. However, thermodynamically, the system will instead cancel the depolarizing field by adjusting the surface stoichiometry. Variation of the polarization and the environmental conditions can thus be used to systematically tune the surface chemistry over a wide range. In addition, we consider the addition of several different catalytic monolayers to the PbTiO3 surface, and we find that additional surface layers can be used to modify the binding of molecules to the surface while still responding to the polarization of the substrate.