Formation of small Pt-Ir bimetallic clusters in NaY zeolite probed with ¹²⁹Xe NMR spectroscopy and ethane hydrogenolysis

Very small (about 1 nm) and homogeneous Pt-Ir bimetallic clusters were formed in the zeolite supercage by calcining NaY co-ion-exchanged with Pt(NH₃)²⁺₄ and Ir(NH₃)₅C1²⁺ at room temperature and subsequent reduction treatment with H₂ at 573 K. These bimetallic clusters were characterized by hydrogen and xenon adsorption, X-ray differaction (XRD), ¹²⁹Xe NMR spectroscopy, and ethane hydrogenolysis reaction. Pt-Ir bimetallic clusters showed specific characteristics different from those of Pt and Ir monometallic clusters and physical mixtures of corresponding monometallic clusters. The chemical shifts of Pt-Ir bimetallic clusters in ¹²⁹Xe NMR and their catalytic activities in ethane hydrogenolysis were lower than those of the corresponding physical mixtures of Pt and Ir monometallic clusters. The activation energies of Pt-Ir bimetallic clusters in ethane hydrogenolysis were smaller than those of monometallic Pt and Ir clusters. The turnover frequencies (TOFs) of bimetallic clusters in ethane hydrogenolysis are widely different from those of monometallic clusters.