Coordinatively Unsaturated Al ³⁺ Centers as Binding Sites for Active Catalyst Phases of Platinum on γ-Al ₂ O ₃

TLDR

Binding of noble metals to reducible oxides occurs at exposed cations, but it is unclear how such binding occurs on nonreducible oxides like alumina. The study employed high‑resolution TEM and solid‑state magic‑angle spinning NMR to investigate platinum anchoring on alumina at high and low loadings. Al³⁺ ions at the alumina surface are penta‑coordinated, and DFT calculations support a model where the cation bonds to three alumina oxygens and two from platinum oxide. Kwak et al.

Abstract

Bonding Oxides and Metals The binding of noble metals that can act as catalysts to metal oxides that are reducible is assumed to occur at the exposed cation of the oxide. For nonreducable oxides such as aluminum oxide, it is not so obvious how the metal can bind strongly. Kwak et al. (p. 1670 ) used a combination of high-resolution transmission electron microscopy and solid-state magic-angle spinning nuclear magnetic resonance to study the anchoring of platinum at high and low loadings on alumina. At the surface, the Al 3+ ions were penta-coordinated. Density functional calculations support a model in which the cation binds three oxygen atoms in the alumina and two from platinum oxide.