Ferroelectric-Based Catalysis: Switchable Surface Chemistry

The maximum efficiency of a fixed catalytic surface occurs when the adsorbate-surface interaction strength is optimal as per the Sabatier principle: strong enough to drive the reactions forward but weak enough to permit the products' desorption. Such a compromise can fundamentally limit catalytic activity. One solution is to create a surface with switchable activity between strong binding (rapid dissociation) and weak binding (easy desorption). On the basis of first-principles theory, we describe a class of catalysts comprising an epitaxial monolayer of a transition metal oxide on an oxide ferroelectric substrate in which reversing the ferroelectric polarization state switches the surface activity between these two limits. As an example, CrO2 monolayer on ferroelectric PbTiO3 permits direct NOx decomposition and CO oxidation while circumventing oxygen and sulfur poisoning. Our computed binding energy trends are explained by a generalization of the canonical d-band model for transition metals to metal oxide surfaces combined with charge transfer effects.