Surface Ir-Ti Alloy Formed via Strong Metal − Support Interaction over Ir/TiO2

The strong metal-support interaction and its chemical nature was examined over a Ir/TiO 2 catalyst, constructed by dispersing 2 nm Ir colloids on the {001} facets of anatase TiO 2 . Air-calcination of the Ir/TiO 2 sample led to the oxidation of Ir particles into IrO x clusters. Upon H 2 -reduction at 573 K, the IrO x species were reduced into metallic with a prominent character for H 2 -chemisrption. As further raising the temperature to 673–773 K for H 2 -reduction, strong metal-support interactions occurred pronouncedly and the amounts of chemically adsorbed hydrogen dropped significantly. Spectroscopic and microscopic analysis found that the formation of surface Ir-Ti alloys on the Ir particles dominated the metal-support interactions, rather than the traditional encapsulation of the metal particles by TiO x overlayers. The surface Ir-Ti alloy, thus formed, promoted the selectivity for hydrogenating the C = O bond in acetophenone by altering the adsorption model of the C = O bond in the substrate. Graphic Abstract