Structural and electrochemical properties of nanostructured nickel silicides by reduction and silicification of high-surface-area nickel oxide

Graphical abstract: Nanostructured nickel silicides have been synthesized by reduction and silification of high-surface-area nickel oxide, and exhibited remarkably like-noble metal property, lower electric resistivity, and ferromagnetism at room temperature. Highlights: ► NiSix have been prepared by reduction and silification of high-surface-area NiO. ► The structure of nickel silicides changed with increasing reaction temperature. ► Si doping into nickel changed the magnetic properties of metallic nickel. ► NiSix have remarkably lower electric resistivity and like-noble metal property. -- Abstract: Nanostructured nickel silicides have been prepared by reduction and silicification of high-surface-area nickel oxide (145 m2 g−1) produced via precipitation. The prepared materials were characterized by nitrogen adsorption, X-ray diffraction, thermal analysis, FT-IR spectroscopy, scanning electron microscopy, transmission electron microscopy, magnetic and electrochemical measurements. The nickel silicide formation involves the following sequence: NiO (cubic) → Ni (cubic) → Ni2Si (orthorhombic) → NiSi (orthorhombic) → NiSi2 (cubic), with particles growing from 13.7 to 21.3 nm. The nickel silicides are ferromagnetic at room temperature, and their saturation magnetization values change drastically with the increase of Si content. Nickel silicides have remarkably low electrical resistivity and noble metal-like properties because of a constriction of the Ni d band and an increase of the electronic density of states. The results suggest that such silicides are promising candidates as inexpensive yet functional materials for applications in electrochemistry as well as catalysis.