Formation of Si Nanowires By Electroreduction of Porous Ni/SiO2 Blocks in Molten CaCl2

Abstract

Electroreduction of porous SiO2 in molten CaCl2 is a promising approach to prepare silicon nanowires (SiNWs) in large quantities. However, it is difficult to control the morphologies and surface topologies of the produced SiNWs. In this work, pure nickel metal powders are added into SiO2, and SiNWs with straight morphology are prepared by electroreduction of solid Ni/SiO2 blocks in molten CaCl2 in a wide temperature range. The prepared SiNWs have a diameter distribution of 80 to 350nm, and nickel silicide is found at the tip of the nanowire. Cyclic voltammograms indicate that nickel does not change the mechanism of electrochemical reduction of SiO2. The growth process of SiNWs is investigated by XRD, FESEM, HRTEM, EDS, and SAED. It is confirmed that nano-sized nickel-silicon droplets formed at the Ni/SiO2/CaCl2 three-phase interface lead the growth of SiNWs, and adding nickel metal into SiO2 can promote the growth of straight nanowires during the electroreduction of Ni/SiO2 in molten CaCl2.