(247b) Synthesis, Characterization and Catalytic Application of Dendrimer-Mediated Nickel and Iron Alloy Nanoparticles Containing An Average of 40 Atoms

Bimetallic nanoparticles (NPs), composed of two different
metals, have recently drawn great interest in the field of catalysis because bimetallization makes it possible to obtain catalysts with
improved catalytic activity that may not be achieved with monometallic
nanoparticles [1]. In addition, the size of the metal particles plays an
important role in the activity and selectivity of catalysts,
and an enhancement in the catalytic properties has been previously shown for
monodisperse particles with ~1nm of diameter [2]. Here we report the synthesis and characterization
of different ratios of Fe-Ni bimetallic nanoparticles of < 2nm diameter
supported on SiO₂ for the study of the catalytic activity in the
ethylene hydrogenation reaction.

The
nanoparticles were synthesized within a hydroxyl-terminated fourth generation
poly-aminoamide (PAMAM) Dendrimer (G4-OH), a hyperbranched
polymer, in aqueous solution and then immobilized by depositing onto a
CAB-O-SIL¨ M-5 Silicon dioxide support. UV-Vis
absorption spectrophotometry was used to monitor the coordination process
between Fe⁽⁺³⁾ and Ni⁽²⁺⁾
metals ions and the internal tertiary amine groups of the dendrimers. Transmission
Electron Microscopy and X-ray absorption spectroscopy were used to measure the
size and distribution of the zerovalent metals after
reduction of the coordinated metal ions. Catalytic activity of the supported Fe-Ni
nanoparticles was studied with ethylene hydrogenation at different temperatures
after hydrogen reduction pretreatment at 523 K.

Reference

1.         J.
H. Sinfelt, Acc. Chem. Res., Vol. 20 p. 134, 1987.

2.         Huang,
W. et al., Nano Letters. Vol. 8, No. 7 p. 2027, 2008.