Controllable synthesis of hexagonal close-packed nickel nanoparticles under high nickel concentration and its catalytic properties

The hexagonal close-packed (hcp) Ni nanoparticles have been synthesized successfully in triethylene glycol with high ionic Ni concentration under the presence of protective agent (PVP or PEG). The protective agent (PVP or PEG) played an important role in the formation of hcp Ni. The crystal structure of nickel can be tuned by changing the concentration of Ni ions, reaction temperature, and amount of protectors. The X-ray diffraction and magnetic studies revealed the formation of pure hcp Ni. The VSM study showed that the magnetic properties of hcp Ni is quite different from that of face-centered cubic (fcc) Ni. The hcp Ni nanoparticle had a low saturation magnetization, while the coercivity value of hcp Ni was nearly the same as that of fcc Ni. A stable hcp Ni supported on γ-Al2O3 catalyst was also prepared successfully for the first time and its catalytic activity was investigated in the aqueous-phase reforming of glycerol. The achieved conversion of glycerol and selectivity to hydrogen was high up to 52 and 64%, while the selectivity to methane was only 5%, indicating the preventing of methanation on hcp Ni.