Size-dependent magnetic and electrocatalytic properties of nickel phosphide nanoparticles

Abstract Nickel phosphide (Ni 2 P) nanoparticles (NPs) with different sizes were synthesized via thermal decomposition of bis(triphenylphosphine)nickel dichloride precursor in the presence of oleylamine. The size of the as-synthesized Ni 2 P NPs could easily be controlled by increasing the reaction temperature from 300 to 340 °C. The structure and morphology were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 adsorption–desorption and X-ray photoelectron spectroscopy (XPS). Then the influences of the size of the Ni 2 P NPs on the magnetic and electrocatalytic properties were investigated systematically. The results indicate that the as-synthesized Ni 2 P NPs exhibit ferromagnetic characteristic at 5 K. The Ni 2 P NPs with small size exhibit superparamagnetism and the larger size exhibit ferromagnetic characteristic at 300 K. The blocking temperature, saturation magnetization, remanent magnetization and coercivity increased significantly with the increase of size of Ni 2 P NPs, indicating the strong size effect of Ni 2 P NPs for magnetic properties. Electrochemical tests indicate that the catalytic activity can be enhanced by decreasing the size of Ni 2 P NPs. Due to the larger electrochemical active surface area and higher electrical conductivity, the Ni 2 P NPs with small size exhibit higher electrocatalytic activity. This work suggests that the size of Ni 2 P NPs is an important factor to affect the magnetic and electrocatalytic properties.