Pinpoint and bulk electrochemical reduction of insulating silicon dioxide to silicon

Abstract

Silicon dioxide (SiO(2)) is conventionally reduced to silicon by carbothermal reduction, in which the oxygen is removed by a heterogeneous-homogeneous reaction sequence at approximately 1,700 degrees C. Here we report pinpoint and bulk electrochemical methods for removing oxygen from solid SiO(2) in a molten CaCl(2) electrolyte at 850 degrees C. This approach involves a 'contacting electrode', in which a metal wire supplies electrons to a selected region of the insulating SiO(2). Bulk reduction of SiO(2) is possible by increasing the number of contacting points. The same method was also demonstrated with molten LiCl-KCl-CaCl(2) at 500 degrees C. The novelty and relative simplicity of this method might lead to new processes in silicon semiconductor technology, as well as in high-purity silicon production. The methodology may be applicable to electrochemical processing of a wide variety of insulating materials, provided that the electrolyte dissolves the appropriate constituent ion(s) of the material.

Reduction of TiO<SUB>2</SUB> in Molten CaCl<SUB>2</SUB> by Ca Deposited during CaO Electrolysis

“…Therefore, the negative electrochemical potential should be supplied to TiO 2 , i.e., TiO 2 should contact with the cathode electrically and accept the electron from the cathode. Okabe et al [22][23][24] and Nohira et al 25) pointed the importance of electron transfer from the cathode to TiO 2 .…”

Facile synthesis of freestanding Si nanowire arrays by one-step template-free electro-deoxidation of SiO2 in a molten salt

“…16,17 In this synthesis, it is found that the electrode structure plays an important role in the growth of Si NWAs. The nickel nets in the sandwich structure of the electrode (Fig.…”

Direct reduction processes for titanium oxide in molten salt

“…Nohira et al (14) reported that CaSi/CaSi 2 and pure Si were obtained above 2.8 V and below 2.45 V, respectively, when the SiO 2 plate was reduced. This indicates the contribution of Ca in the formation of Ca-based alloys, but a less active Ca does not form these alloys although it can reduce SiO 2 .…”