Dispersion and support dictated properties and activities of Pt/metal oxide catalysts in heterogeneous CO oxidation

The source of activity of metal/metal oxides has always been an interesting, important but highly challenging research topic in heterogeneous catalysis. In CO oxidation reaction, this work clarifies dispersion and support dictated activities of Pt including single-atom (Pt 1 ), 2.8 nm (Pt NP-S ) and 36 nm (Pt NP-L ) Pt supported on both reducible TiO 2 and “inert” Al 2 O 3 supports. The X-ray absorption fine structure (XAFS) shows that chemical state of Pt is affected by both dispersion and support: Pt 1 presents fully oxidized state in both Pt 1 /TiO 2 and Pt 1 /Al 2 O 3 ; Pt NP-S in Pt NP-S /TiO 2 appear nearly oxidized state while about half of Pt is metallic state in Pt NP-S /Al 2 O 3 ; Pt NP-L in both Pt NP-L /TiO 2 and Pt NP-L /Al 2 O 3 exhibit metallic state. All the Pt species supported on TiO 2 present much lower apparent activation barriers ( E app ) than that on Al 2 O 3 . Moreover, Pt 1 /TiO 2 possesses dozen times of efficiency than Pt NP-S /TiO 2 although they have similar E app values. A truth is finally made clear that a reducible metal oxide with low oxygen vacancy formation energy is critical to endow Pt/metal oxide a high activity and the single-atom dispersion of Pt is the way to maximize the active sites of Pt/metal oxide.