Diffusion-Limited Formation of Nonequilibrium Intermetallic Nanophase for Selective Dehydrogenation

Nonequilibrium intermetallic phases in the nanoscale were realized by diffusion-controlled solid-state transformation, forming SiO₂ supported NPs with Pd core and a CsCl type Pd₁M₁ shell, where M is Sn or Sb. The core-shell geometry is identified from scanning transmission electron microscopy and infrared spectroscopy and the crystal structure is confirmed from in situ synchrotron X-ray diffraction and X-ray absorption spectroscopy. The highly symmetric Pd₁M₁ intermetallic phase has not been reported previously and contains catalytic ensembles with high selectivity toward dehydrogenation of propane. The kinetically limited solid-state reaction is generally applicable to nanoparticle synthesis and could produce materials with desired structures and properties beyond conventional structural limits.