Electrochemical preparation of silicon nanowires from porous NiO/SiO2 blocks in molten CaCl2

•Si nanowires were produced by the electrolysis of porous NiO/SiO2 blocks.•The addition of NiO powders seeds the growth of straight silicon nanowires.•Nano-sized nickel silicide particles were observed in the body of a nanowire.

Silicon nanowires (SiNWs) were produced by the electrochemical reduction of porous NiO/SiO2 blocks ([SiO2]/[NiO]=10 M ratio) in molten CaCl2 at 1173 K for the first time. NiO additives seed the growth of straight SiNWs. The produced SiNWs have diameter distributions ranging from 60 to 330 nm and outer amorphous layers with thickness about 2.5–3.1 nm. The length of the nanowire can be as long as 30 µm. The high length-to-diameter suggests that silicon is incorporated through the tip of the nanowire. Nano-sized nickel silicide particles are observed in the body of a zigzag SiNW. The results indicate that the electrochemical reduction process has the potential to produce nano-sized Si-based composite and metal silicide.