Ultimate dispersion of metallic and ionic platinum on ceria

Abstract

Ceria represents a technologically indispensable reducible catalyst support. Besides the general impact on the surface chemistry, the oxygen content of the ceria surface directly influences the dispersion of ceria-supported metal nanoparticles, and the properties of ceria-supported metal catalysts. We investigate the role of oxygen atoms on a CeO₂(111) surface in supporting Pt as smallest metallic Pt clusters or, concurrently, as monodispersed Pt²⁺ ions. We demonstrate that the necessary condition for the formation of Pt²⁺ ions is the availability of lattice O or excess O atoms at surface step edges. Although Pt²⁺ ions can exist on partially reduced surfaces, excess O atoms are required to maximize the capacity of the surface to accommodate Pt²⁺ and to trigger the redispersion of metallic Pt clusters. Our study provides atomic-level understanding and control of the highest dispersions of Pt on the ceria surface for advancing the state-of-the-art Pt/ceria catalysts that are presently identified at the verge of single-atom Pt dispersion.