Highly dispersed Pt–Ir nanoparticles on titania nanotubes

Bimetal ∼1.4 nm Pt–Ir nanoparticles were homogeneously dispersed on titania nanotubes by a conventional successive wet impregnation method, by first adding Ir and then, the Pt chloride precursors. Ir precursor interacts strongly with the nanotubular surface yielding highly dispersed ∼1.4 nm nanoparticles, and later acts as a nucleation site for the assembly of Pt atoms. The mean sizes of Ir, Pt–Ir were 1.4 nm and that of Pt nanoparticles was 3.5 nm. Bimetal Pt–Ir nanoparticles were more active in cyclohexene (CHE) disproportionation reaction than the corresponding monometal catalysts. At reaction temperatures <423 K, CHE is hydrogenated to cyclohexane (CHA) as the main product, whereas at >473 K, CHE is dehydrogenated to produce mainly benzene (BZ). The activity of Pt–Ir nanoparticles increased as the reduction temperature rose from 573 to 673 K, suggesting that electronic transfer between reducible NT support and metal nanoparticles favors CHE hydrogenation/dehydrogenation, which is a structure insensitive reaction.

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► 1.4 nm Pt–Ir nanoparticles homogeneously dispersed on titania nanotubes.
► Ir nanoparticles act as nucleation sites for Pt atoms assembly.
► Pt–Ir nanoparticles were more active for cyclohexene hydrogenation than Pt or Ir nanoparticles.